11 files changed, 452 insertions, 1120 deletions

diff --git a/doc/builders/packages/kakoune.xml b/doc/builders/packages/kakoune.xml
index 728d40dacc92f..045dbd0a653bf 100644
--- a/doc/builders/packages/kakoune.xml
+++ b/doc/builders/packages/kakoune.xml
@@ -6,9 +6,7 @@
  <para>
   Kakoune can be built to autoload plugins:
 <programlisting>(kakoune.override {
-  configure = {
-    plugins = with pkgs.kakounePlugins; [ parinfer-rust ];
-  };
+  plugins = with pkgs.kakounePlugins; [ parinfer-rust ];
 })</programlisting>
  </para>
 </section>
diff --git a/doc/builders/packages/opengl.xml b/doc/builders/packages/opengl.xml
index 5f4433a288446..dfd64b1885863 100644
--- a/doc/builders/packages/opengl.xml
+++ b/doc/builders/packages/opengl.xml
@@ -4,6 +4,6 @@
  <title>OpenGL</title>
 
  <para>
-  Packages that use OpenGL have NixOS desktop as their primary target. The current solution for loading the GPU-specific drivers is based on <literal>libglvnd</literal> and looks for the driver implementation in <literal>LD_LIBRARY_PATH</literal>. If you are using a non-NixOS GNU/Linux/X11 desktop with free software video drivers, consider launching OpenGL-dependent programs from Nixpkgs with Nixpkgs versions of <literal>libglvnd</literal> and <literal>mesa_drivers</literal> in <literal>LD_LIBRARY_PATH</literal>. For proprietary video drivers you might have luck with also adding the corresponding video driver package.
+  Packages that use OpenGL have NixOS desktop as their primary target. The current solution for loading the GPU-specific drivers is based on <literal>libglvnd</literal> and looks for the driver implementation in <literal>LD_LIBRARY_PATH</literal>. If you are using a non-NixOS GNU/Linux/X11 desktop with free software video drivers, consider launching OpenGL-dependent programs from Nixpkgs with Nixpkgs versions of <literal>libglvnd</literal> and <literal>mesa.drivers</literal> in <literal>LD_LIBRARY_PATH</literal>. For proprietary video drivers you might have luck with also adding the corresponding video driver package.
  </para>
 </section>
diff --git a/doc/contributing/coding-conventions.xml b/doc/contributing/coding-conventions.xml
index fcb6501f61599..e587275a63836 100644
--- a/doc/contributing/coding-conventions.xml
+++ b/doc/contributing/coding-conventions.xml
@@ -524,6 +524,16 @@ args.stdenv.mkDerivation (args // {
        </varlistentry>
        <varlistentry>
         <term>
+         If it’s a <emphasis>terminal emulator</emphasis>:
+        </term>
+        <listitem>
+         <para>
+          <filename>applications/terminal-emulators</filename> (e.g. <filename>alacritty</filename> or <filename>rxvt</filename> or <filename>termite</filename>)
+         </para>
+        </listitem>
+       </varlistentry>
+       <varlistentry>
+        <term>
          If it’s for <emphasis>video playback / editing</emphasis>:
         </term>
         <listitem>
diff --git a/doc/languages-frameworks/agda.section.md b/doc/languages-frameworks/agda.section.md
index 9ce046d05b6f0..5ba4e285f424d 100644
--- a/doc/languages-frameworks/agda.section.md
+++ b/doc/languages-frameworks/agda.section.md
@@ -12,12 +12,13 @@ Agda can be installed from `agda`:
 $ nix-env -iA agda
 ```
 
-To use agda with libraries, the `agda.withPackages` function can be used. This function either takes:
-+ A list of packages,
-+ or a function which returns a list of packages when given the `agdaPackages` attribute set,
-+ or an attribute set containing a list of packages and a GHC derivation for compilation (see below).
+To use Agda with libraries, the `agda.withPackages` function can be used. This function either takes:
 
-For example, suppose we wanted a version of agda which has access to the standard library. This can be obtained with the expressions:
+* A list of packages,
+* or a function which returns a list of packages when given the `agdaPackages` attribute set,
+* or an attribute set containing a list of packages and a GHC derivation for compilation (see below).
+
+For example, suppose we wanted a version of Agda which has access to the standard library. This can be obtained with the expressions:
 
 ```
 agda.withPackages [ agdaPackages.standard-library ]
@@ -33,18 +34,19 @@ or can be called as in the [Compiling Agda](#compiling-agda) section.
 
 If you want to use a library in your home directory (for instance if it is a development version) then typecheck it manually (using `agda.withPackages` if necessary) and then override the `src` attribute of the package to point to your local repository.
 
-Agda will not by default use these libraries. To tell agda to use the library we have some options:
-- Call `agda` with the library flag:
+Agda will not by default use these libraries. To tell Agda to use the library we have some options:
+
+* Call `agda` with the library flag:
 ```
 $ agda -l standard-library -i . MyFile.agda
 ```
-- Write a `my-library.agda-lib` file for the project you are working on which may look like:
+* Write a `my-library.agda-lib` file for the project you are working on which may look like:
 ```
 name: my-library
 include: .
 depend: standard-library
 ```
-- Create the file `~/.agda/defaults` and add any libraries you want to use by default.
+* Create the file `~/.agda/defaults` and add any libraries you want to use by default.
 
 More information can be found in the [official Agda documentation on library management](https://agda.readthedocs.io/en/v2.6.1/tools/package-system.html).
 
@@ -60,12 +62,13 @@ agda.withPackages {
 ```
 
 ## Writing Agda packages
-To write a nix derivation for an agda library, first check that the library has a `*.agda-lib` file.
+To write a nix derivation for an Agda library, first check that the library has a `*.agda-lib` file.
 
 A derivation can then be written using `agdaPackages.mkDerivation`. This has similar arguments to `stdenv.mkDerivation` with the following additions:
-+ `everythingFile` can be used to specify the location of the `Everything.agda` file, defaulting to `./Everything.agda`. If this file does not exist then either it should be patched in or the `buildPhase` should be overridden (see below).
-+ `libraryName` should be the name that appears in the `*.agda-lib` file, defaulting to `pname`.
-+ `libraryFile` should be the file name of the `*.agda-lib` file, defaulting to `${libraryName}.agda-lib`.
+
+* `everythingFile` can be used to specify the location of the `Everything.agda` file, defaulting to `./Everything.agda`. If this file does not exist then either it should be patched in or the `buildPhase` should be overridden (see below).
+* `libraryName` should be the name that appears in the `*.agda-lib` file, defaulting to `pname`.
+* `libraryFile` should be the file name of the `*.agda-lib` file, defaulting to `${libraryName}.agda-lib`.
 
 ### Building Agda packages
 The default build phase for `agdaPackages.mkDerivation` simply runs `agda` on the `Everything.agda` file.
@@ -74,12 +77,14 @@ Additionally, a `preBuild` or `configurePhase` can be used if there are steps th
 `agda` and the Agda libraries contained in `buildInputs` are made available during the build phase.
 
 ### Installing Agda packages
-The default install phase copies agda source files, agda interface files (`*.agdai`) and `*.agda-lib` files to the output directory.
+The default install phase copies Agda source files, Agda interface files (`*.agdai`) and `*.agda-lib` files to the output directory.
 This can be overridden.
 
-By default, agda sources are files ending on  `.agda`, or literate agda files ending on `.lagda`, `.lagda.tex`, `.lagda.org`, `.lagda.md`, `.lagda.rst`. The list of recognised agda source extensions can be extended by setting the `extraExtensions` config variable.
+By default, Agda sources are files ending on `.agda`, or literate Agda files ending on `.lagda`, `.lagda.tex`, `.lagda.org`, `.lagda.md`, `.lagda.rst`. The list of recognised Agda source extensions can be extended by setting the `extraExtensions` config variable.
+
+## Adding Agda packages to Nixpkgs
 
-To add an agda package to `nixpkgs`, the derivation should be written to `pkgs/development/libraries/agda/${library-name}/` and an entry should be added to `pkgs/top-level/agda-packages.nix`. Here it is called in a scope with access to all other agda libraries, so the top line of the `default.nix` can look like:
+To add an Agda package to `nixpkgs`, the derivation should be written to `pkgs/development/libraries/agda/${library-name}/` and an entry should be added to `pkgs/top-level/agda-packages.nix`. Here it is called in a scope with access to all other Agda libraries, so the top line of the `default.nix` can look like:
 ```
 { mkDerivation, standard-library, fetchFromGitHub }:
 ```
@@ -103,4 +108,4 @@ mkDerivation {
 ```
 This library has a file called `.agda-lib`, and so we give an empty string to `libraryFile` as nothing precedes `.agda-lib` in the filename. This file contains `name: IAL-1.3`, and so we let `libraryName =  "IAL-1.3"`. This library does not use an `Everything.agda` file and instead has a Makefile, so there is no need to set `everythingFile` and we set a custom `buildPhase`.
 
-When writing an agda package it is essential to make sure that no `.agda-lib` file gets added to the store as a single file (for example by using `writeText`). This causes agda to think that the nix store is a agda library and it will attempt to write to it whenever it typechecks something. See [https://github.com/agda/agda/issues/4613](https://github.com/agda/agda/issues/4613).
+When writing an Agda package it is essential to make sure that no `.agda-lib` file gets added to the store as a single file (for example by using `writeText`). This causes Agda to think that the nix store is a Agda library and it will attempt to write to it whenever it typechecks something. See [https://github.com/agda/agda/issues/4613](https://github.com/agda/agda/issues/4613).
diff --git a/doc/languages-frameworks/haskell.section.md b/doc/languages-frameworks/haskell.section.md
index cba4d0561b074..67318a5b74671 100644
--- a/doc/languages-frameworks/haskell.section.md
+++ b/doc/languages-frameworks/haskell.section.md
@@ -3,1092 +3,11 @@ title: User's Guide for Haskell in Nixpkgs
 author: Peter Simons
 date: 2015-06-01
 ---
-# Haskell
-
-
-## How to install Haskell packages
-
-Nixpkgs distributes build instructions for all Haskell packages registered on
-[Hackage](http://hackage.haskell.org/), but strangely enough normal Nix package
-lookups don't seem to discover any of them, except for the default version of ghc, cabal-install, and stack:
-```
-$ nix-env -i alex
-error: selector ‘alex’ matches no derivations
-$ nix-env -qa ghc
-ghc-7.10.2
-```
-
-The Haskell package set is not registered in the top-level namespace because it
-is *huge*. If all Haskell packages were visible to these commands, then
-name-based search/install operations would be much slower than they are now. We
-avoided that by keeping all Haskell-related packages in a separate attribute
-set called `haskellPackages`, which the following command will list:
-```
-$ nix-env -f "<nixpkgs>" -qaP -A haskellPackages
-haskellPackages.a50                                             a50-0.5
-haskellPackages.AAI                                             AAI-0.2.0.1
-haskellPackages.abacate                                         abacate-0.0.0.0
-haskellPackages.abc-puzzle                                      abc-puzzle-0.2.1
-haskellPackages.abcBridge                                       abcBridge-0.15
-haskellPackages.abcnotation                                     abcnotation-1.9.0
-haskellPackages.abeson                                          abeson-0.1.0.1
-[... some 14000 entries omitted  ...]
-```
-
-To install any of those packages into your profile, refer to them by their
-attribute path (first column):
-```shell
-nix-env -f "<nixpkgs>" -iA haskellPackages.Allure ...
-```
-
-The attribute path of any Haskell packages corresponds to the name of that
-particular package on Hackage: the package `cabal-install` has the attribute
-`haskellPackages.cabal-install`, and so on. (Actually, this convention causes
-trouble with packages like `3dmodels` and `4Blocks`, because these names are
-invalid identifiers in the Nix language. The issue of how to deal with these
-rare corner cases is currently unresolved.)
-
-Haskell packages whose Nix name (second column) begins with a `haskell-` prefix
-are packages that provide a library whereas packages without that prefix
-provide just executables. Libraries may provide executables too, though: the
-package `haskell-pandoc`, for example, installs both a library and an
-application. You can install and use Haskell executables just like any other
-program in Nixpkgs, but using Haskell libraries for development is a bit
-trickier and we'll address that subject in great detail in section [How to
-create a development environment](#how-to-create-a-development-environment).
-
-Attribute paths are deterministic inside of Nixpkgs, but the path necessary to
-reach Nixpkgs varies from system to system. We dodged that problem by giving
-`nix-env` an explicit `-f "<nixpkgs>"` parameter, but if you call `nix-env`
-without that flag, then chances are the invocation fails:
-```
-$ nix-env -iA haskellPackages.cabal-install
-error: attribute ‘haskellPackages’ in selection path
-       ‘haskellPackages.cabal-install’ not found
-```
-
-On NixOS, for example, Nixpkgs does *not* exist in the top-level namespace by
-default. To figure out the proper attribute path, it's easiest to query for the
-path of a well-known Nixpkgs package, i.e.:
-```
-$ nix-env -qaP coreutils
-nixos.coreutils  coreutils-8.23
-```
-
-If your system responds like that (most NixOS installations will), then the
-attribute path to `haskellPackages` is `nixos.haskellPackages`. Thus, if you
-want to use `nix-env` without giving an explicit `-f` flag, then that's the way
-to do it:
-```shell
-nix-env -qaP -A nixos.haskellPackages
-nix-env -iA nixos.haskellPackages.cabal-install
-```
-
-Our current default compiler is GHC 8.8.x and the `haskellPackages` set
-contains packages built with that particular version. Nixpkgs contains the last
-three major releases of GHC and there is a whole family of package sets
-available that defines Hackage packages built with each of those compilers,
-too:
-```shell
-nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc865
-nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc8101
-```
-
-The name `haskellPackages` is really just a synonym for
-`haskell.packages.ghc882`, because we prefer that package set internally and
-recommend it to our users as their default choice, but ultimately you are free
-to compile your Haskell packages with any GHC version you please. The following
-command displays the complete list of available compilers:
-```
-$ nix-env -f "<nixpkgs>" -qaP -A haskell.compiler
-haskell.compiler.ghc8101                 ghc-8.10.1
-haskell.compiler.integer-simple.ghc8101  ghc-8.10.1
-haskell.compiler.ghcHEAD                 ghc-8.11.20200505
-haskell.compiler.integer-simple.ghcHEAD  ghc-8.11.20200505
-haskell.compiler.ghc822Binary            ghc-8.2.2-binary
-haskell.compiler.ghc844                  ghc-8.4.4
-haskell.compiler.ghc863Binary            ghc-8.6.3-binary
-haskell.compiler.ghc865                  ghc-8.6.5
-haskell.compiler.integer-simple.ghc865   ghc-8.6.5
-haskell.compiler.ghc882                  ghc-8.8.2
-haskell.compiler.integer-simple.ghc882   ghc-8.8.2
-haskell.compiler.ghc883                  ghc-8.8.3
-haskell.compiler.integer-simple.ghc883   ghc-8.8.3
-haskell.compiler.ghcjs                   ghcjs-8.6.0.1
-```
-
-We have no package sets for `jhc` or `uhc` yet, unfortunately, but for every
-version of GHC listed above, there exists a package set based on that compiler.
-Also, the attributes `haskell.compiler.ghcXYC` and
-`haskell.packages.ghcXYC.ghc` are synonymous for the sake of convenience.
-
-## How to create a development environment
-
-### How to install a compiler
-
-A simple development environment consists of a Haskell compiler and one or both
-of the tools `cabal-install` and `stack`. We saw in section
-[How to install Haskell packages](#how-to-install-haskell-packages) how you can install those programs into your
-user profile:
-```shell
-nix-env -f "<nixpkgs>" -iA haskellPackages.ghc haskellPackages.cabal-install
-```
-
-Instead of the default package set `haskellPackages`, you can also use the more
-precise name `haskell.compiler.ghc7102`, which has the advantage that it refers
-to the same GHC version regardless of what Nixpkgs considers "default" at any
-given time.
-
-Once you've made those tools available in `$PATH`, it's possible to build
-Hackage packages the same way people without access to Nix do it all the time:
-```shell
-cabal get lens-4.11 && cd lens-4.11
-cabal install -j --dependencies-only
-cabal configure
-cabal build
-```
-
-If you enjoy working with Cabal sandboxes, then that's entirely possible too:
-just execute the command
-```shell
-cabal sandbox init
-```
-before installing the required dependencies.
-
-The `nix-shell` utility makes it easy to switch to a different compiler
-version; just enter the Nix shell environment with the command
-```shell
-nix-shell -p haskell.compiler.ghc784
-```
-to bring GHC 7.8.4 into `$PATH`. Alternatively, you can use Stack instead of
-`nix-shell` directly to select compiler versions and other build tools
-per-project. It uses `nix-shell` under the hood when Nix support is turned on.
-See [How to build a Haskell project using Stack](#how-to-build-a-haskell-project-using-stack).
-
-If you're using `cabal-install`, re-running `cabal configure` inside the spawned
-shell switches your build to use that compiler instead. If you're working on
-a project that doesn't depend on any additional system libraries outside of GHC,
-then it's even sufficient to just run the `cabal configure` command inside of
-the shell:
-```shell
-nix-shell -p haskell.compiler.ghc784 --command "cabal configure"
-```
-
-Afterwards, all other commands like `cabal build` work just fine in any shell
-environment, because the configure phase recorded the absolute paths to all
-required tools like GHC in its build configuration inside of the `dist/`
-directory. Please note, however, that `nix-collect-garbage` can break such an
-environment because the Nix store paths created by `nix-shell` aren't "alive"
-anymore once `nix-shell` has terminated. If you find that your Haskell builds
-no longer work after garbage collection, then you'll have to re-run `cabal
-configure` inside of a new `nix-shell` environment.
-
-### How to install a compiler with libraries
-
-GHC expects to find all installed libraries inside of its own `lib` directory.
-This approach works fine on traditional Unix systems, but it doesn't work for
-Nix, because GHC's store path is immutable once it's built. We cannot install
-additional libraries into that location. As a consequence, our copies of GHC
-don't know any packages except their own core libraries, like `base`,
-`containers`, `Cabal`, etc.
-
-We can register additional libraries to GHC, however, using a special build
-function called `ghcWithPackages`. That function expects one argument: a
-function that maps from an attribute set of Haskell packages to a list of
-packages, which determines the libraries known to that particular version of
-GHC. For example, the Nix expression `ghcWithPackages (pkgs: [pkgs.mtl])`
-generates a copy of GHC that has the `mtl` library registered in addition to
-its normal core packages:
-```
-$ nix-shell -p "haskellPackages.ghcWithPackages (pkgs: [pkgs.mtl])"
-
-[nix-shell:~]$ ghc-pkg list mtl
-/nix/store/zy79...-ghc-7.10.2/lib/ghc-7.10.2/package.conf.d:
-    mtl-2.2.1
-```
-
-This function allows users to define their own development environment by means
-of an override. After adding the following snippet to `~/.config/nixpkgs/config.nix`,
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    myHaskellEnv = self.haskell.packages.ghc7102.ghcWithPackages
-                     (haskellPackages: with haskellPackages; [
-                       # libraries
-                       arrows async cgi criterion
-                       # tools
-                       cabal-install haskintex
-                     ]);
-  };
-}
-```
-it's possible to install that compiler with `nix-env -f "<nixpkgs>" -iA
-myHaskellEnv`. If you'd like to switch that development environment to a
-different version of GHC, just replace the `ghc7102` bit in the previous
-definition with the appropriate name. Of course, it's also possible to define
-any number of these development environments! (You can't install two of them
-into the same profile at the same time, though, because that would result in
-file conflicts.)
-
-The generated `ghc` program is a wrapper script that re-directs the real
-GHC executable to use a new `lib` directory --- one that we specifically
-constructed to contain all those packages the user requested:
-```
-$ cat $(type -p ghc)
-#! /nix/store/xlxj...-bash-4.3-p33/bin/bash -e
-export NIX_GHC=/nix/store/19sm...-ghc-7.10.2/bin/ghc
-export NIX_GHCPKG=/nix/store/19sm...-ghc-7.10.2/bin/ghc-pkg
-export NIX_GHC_DOCDIR=/nix/store/19sm...-ghc-7.10.2/share/doc/ghc/html
-export NIX_GHC_LIBDIR=/nix/store/19sm...-ghc-7.10.2/lib/ghc-7.10.2
-exec /nix/store/j50p...-ghc-7.10.2/bin/ghc "-B$NIX_GHC_LIBDIR" "$@"
-```
-
-The variables `$NIX_GHC`, `$NIX_GHCPKG`, etc. point to the *new* store path
-`ghcWithPackages` constructed specifically for this environment. The last line
-of the wrapper script then executes the real `ghc`, but passes the path to the
-new `lib` directory using GHC's `-B` flag.
-
-The purpose of those environment variables is to work around an impurity in the
-popular [ghc-paths](http://hackage.haskell.org/package/ghc-paths) library. That
-library promises to give its users access to GHC's installation paths. Only,
-the library can't possible know that path when it's compiled, because the path
-GHC considers its own is determined only much later, when the user configures
-it through `ghcWithPackages`. So we [patched
-ghc-paths](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/patches/ghc-paths-nix.patch)
-to return the paths found in those environment variables at run-time rather
-than trying to guess them at compile-time.
-
-To make sure that mechanism works properly all the time, we recommend that you
-set those variables to meaningful values in your shell environment, too, i.e.
-by adding the following code to your `~/.bashrc`:
-```bash
-if type >/dev/null 2>&1 -p ghc; then
-  eval "$(egrep ^export "$(type -p ghc)")"
-fi
-```
-
-If you are certain that you'll use only one GHC environment which is located in
-your user profile, then you can use the following code, too, which has the
-advantage that it doesn't contain any paths from the Nix store, i.e. those
-settings always remain valid even if a `nix-env -u` operation updates the GHC
-environment in your profile:
-```bash
-if [ -e ~/.nix-profile/bin/ghc ]; then
-  export NIX_GHC="$HOME/.nix-profile/bin/ghc"
-  export NIX_GHCPKG="$HOME/.nix-profile/bin/ghc-pkg"
-  export NIX_GHC_DOCDIR="$HOME/.nix-profile/share/doc/ghc/html"
-  export NIX_GHC_LIBDIR="$HOME/.nix-profile/lib/ghc-$($NIX_GHC --numeric-version)"
-fi
-```
-
-### How to install a compiler with libraries, hoogle and documentation indexes
-
-If you plan to use your environment for interactive programming, not just
-compiling random Haskell code, you might want to replace `ghcWithPackages` in
-all the listings above with `ghcWithHoogle`.
-
-This environment generator not only produces an environment with GHC and all
-the specified libraries, but also generates a `hoogle` and `haddock` indexes
-for all the packages, and provides a wrapper script around `hoogle` binary that
-uses all those things. A precise name for this thing would be
-"`ghcWithPackagesAndHoogleAndDocumentationIndexes`", which is, regrettably, too
-long and scary.
-
-For example, installing the following environment
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    myHaskellEnv = self.haskellPackages.ghcWithHoogle
-                     (haskellPackages: with haskellPackages; [
-                       # libraries
-                       arrows async cgi criterion
-                       # tools
-                       cabal-install haskintex
-                     ]);
-  };
-}
-```
-allows one to browse module documentation index [not too dissimilar to
-this](https://downloads.haskell.org/~ghc/latest/docs/html/libraries/index.html)
-for all the specified packages and their dependencies by directing a browser of
-choice to `~/.nix-profile/share/doc/hoogle/index.html` (or
-`/run/current-system/sw/share/doc/hoogle/index.html` in case you put it in
-`environment.systemPackages` in NixOS).
-
-After you've marveled enough at that try adding the following to your
-`~/.ghc/ghci.conf`
-```
-:def hoogle \s -> return $ ":! hoogle search -cl --count=15 \"" ++ s ++ "\""
-:def doc \s -> return $ ":! hoogle search -cl --info \"" ++ s ++ "\""
-```
-and test it by typing into `ghci`:
-```
-:hoogle a -> a
-:doc a -> a
-```
-
-Be sure to note the links to `haddock` files in the output. With any modern and
-properly configured terminal emulator you can just click those links to
-navigate there.
-
-Finally, you can run
-```shell
-hoogle server --local -p 8080
-```
-and navigate to http://localhost:8080/ for your own local
-[Hoogle](https://www.haskell.org/hoogle/). The `--local` flag makes the hoogle
-server serve files from your nix store over http, without the flag it will use
-`file://` URIs. Note, however, that Firefox and possibly other browsers
-disallow navigation from `http://` to `file://` URIs for security reasons,
-which might be quite an inconvenience. Versions before v5 did not have this
-flag. See
-[this page](http://kb.mozillazine.org/Links_to_local_pages_do_not_work) for
-workarounds.
-
-For NixOS users there's a service which runs this exact command for you.
-Specify the `packages` you want documentation for and the `haskellPackages` set
-you want them to come from. Add the following to `configuration.nix`.
-
-```nix
-services.hoogle = {
-  enable = true;
-  packages = (hpkgs: with hpkgs; [text cryptonite]);
-  haskellPackages = pkgs.haskellPackages;
-};
-```
-
-### How to build a Haskell project using Stack
-
-[Stack](http://haskellstack.org) is a popular build tool for Haskell projects.
-It has first-class support for Nix. Stack can optionally use Nix to
-automatically select the right version of GHC and other build tools to build,
-test and execute apps in an existing project downloaded from somewhere on the
-Internet. Pass the `--nix` flag to any `stack` command to do so, e.g.
-```shell
-git clone --recurse-submodules https://github.com/yesodweb/wai.git
-cd wai
-stack --nix build
-```
-
-If you want `stack` to use Nix by default, you can add a `nix` section to the
-`stack.yaml` file, as explained in the [Stack documentation][stack-nix-doc]. For
-example:
-```yaml
-nix:
-  enable: true
-  packages: [pkgconfig zeromq zlib]
-```
-
-The example configuration snippet above tells Stack to create an ad hoc
-environment for `nix-shell` as in the below section, in which the `pkgconfig`,
-`zeromq` and `zlib` packages from Nixpkgs are available. All `stack` commands
-will implicitly be executed inside this ad hoc environment.
-
-Some projects have more sophisticated needs. For examples, some ad hoc
-environments might need to expose Nixpkgs packages compiled in a certain way, or
-with extra environment variables. In these cases, you'll need a `shell` field
-instead of `packages`:
-```yaml
-nix:
-  enable: true
-  shell-file: shell.nix
-```
-
-For more on how to write a `shell.nix` file see the below section. You'll need
-to express a derivation. Note that Nixpkgs ships with a convenience wrapper
-function around `mkDerivation` called `haskell.lib.buildStackProject` to help you
-create this derivation in exactly the way Stack expects. However for this to work
-you need to disable the sandbox, which you can do by using `--option sandbox relaxed`
-or `--option sandbox false` to the Nix command. All of the same inputs
-as `mkDerivation` can be provided. For example, to build a Stack project that
-including packages that link against a version of the R library compiled with
-special options turned on:
-```nix
-with (import <nixpkgs> { });
-
-let R = pkgs.R.override { enableStrictBarrier = true; };
-in
-haskell.lib.buildStackProject {
-  name = "HaskellR";
-  buildInputs = [ R zeromq zlib ];
-}
-```
-
-You can select a particular GHC version to compile with by setting the
-`ghc` attribute as an argument to `buildStackProject`. Better yet, let
-Stack choose what GHC version it wants based on the snapshot specified
-in `stack.yaml` (only works with Stack >= 1.1.3):
-```nix
-{nixpkgs ? import <nixpkgs> { }, ghc ? nixpkgs.ghc}:
-
-with nixpkgs;
-
-let R = pkgs.R.override { enableStrictBarrier = true; };
-in
-haskell.lib.buildStackProject {
-  name = "HaskellR";
-  buildInputs = [ R zeromq zlib ];
-  inherit ghc;
-}
-```
-
-[stack-nix-doc]: http://docs.haskellstack.org/en/stable/nix_integration.html
-
-### How to create ad hoc environments for `nix-shell`
-
-The easiest way to create an ad hoc development environment is to run
-`nix-shell` with the appropriate GHC environment given on the command-line:
-```shell
-nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [mtl pandoc])"
-```
-
-For more sophisticated use-cases, however, it's more convenient to save the
-desired configuration in a file called `shell.nix` that looks like this:
-```nix
-{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
-let
-  inherit (nixpkgs) pkgs;
-  ghc = pkgs.haskell.packages.${compiler}.ghcWithPackages (ps: with ps; [
-          monad-par mtl
-        ]);
-in
-pkgs.stdenv.mkDerivation {
-  name = "my-haskell-env-0";
-  buildInputs = [ ghc ];
-  shellHook = "eval $(egrep ^export ${ghc}/bin/ghc)";
-}
-```
-
-Now run `nix-shell` --- or even `nix-shell --pure` --- to enter a shell
-environment that has the appropriate compiler in `$PATH`. If you use `--pure`,
-then add all other packages that your development environment needs into the
-`buildInputs` attribute. If you'd like to switch to a different compiler
-version, then pass an appropriate `compiler` argument to the expression, i.e.
-`nix-shell --argstr compiler ghc784`.
-
-If you need such an environment because you'd like to compile a Hackage package
-outside of Nix --- i.e. because you're hacking on the latest version from Git
----, then the package set provides suitable nix-shell environments for you
-already! Every Haskell package has an `env` attribute that provides a shell
-environment suitable for compiling that particular package. If you'd like to
-hack the `lens` library, for example, then you just have to check out the
-source code and enter the appropriate environment:
-```
-$ cabal get lens-4.11 && cd lens-4.11
-Downloading lens-4.11...
-Unpacking to lens-4.11/
-
-$ nix-shell "<nixpkgs>" -A haskellPackages.lens.env
-[nix-shell:/tmp/lens-4.11]$
-```
-
-At point, you can run `cabal configure`, `cabal build`, and all the other
-development commands. Note that you need `cabal-install` installed in your
-`$PATH` already to use it here --- the `nix-shell` environment does not provide
-it.
-
-## How to create Nix builds for your own private Haskell packages
-
-If your own Haskell packages have build instructions for Cabal, then you can
-convert those automatically into build instructions for Nix using the
-`cabal2nix` utility, which you can install into your profile by running
-`nix-env -i cabal2nix`.
-
-### How to build a stand-alone project
-
-For example, let's assume that you're working on a private project called
-`foo`. To generate a Nix build expression for it, change into the project's
-top-level directory and run the command:
-```shell
-cabal2nix . > foo.nix
-```
-Then write the following snippet into a file called `default.nix`:
-```nix
-{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
-nixpkgs.pkgs.haskell.packages.${compiler}.callPackage ./foo.nix { }
-```
-
-Finally, store the following code in a file called `shell.nix`:
-```nix
-{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
-(import ./default.nix { inherit nixpkgs compiler; }).env
-```
-
-At this point, you can run `nix-build` to have Nix compile your project and
-install it into a Nix store path. The local directory will contain a symlink
-called `result` after `nix-build` returns that points into that location. Of
-course, passing the flag `--argstr compiler ghc763` allows switching the build
-to any version of GHC currently supported.
-
-Furthermore, you can call `nix-shell` to enter an interactive development
-environment in which you can use `cabal configure` and `cabal build` to develop
-your code. That environment will automatically contain a proper GHC derivation
-with all the required libraries registered as well as all the system-level
-libraries your package might need.
-
-If your package does not depend on any system-level libraries, then it's
-sufficient to run
-```shell
-nix-shell --command "cabal configure"
-```
-once to set up your build. `cabal-install` determines the absolute paths to all
-resources required for the build and writes them into a config file in the
-`dist/` directory. Once that's done, you can run `cabal build` and any other
-command for that project even outside of the `nix-shell` environment. This
-feature is particularly nice for those of us who like to edit their code with
-an IDE, like Emacs' `haskell-mode`, because it's not necessary to start Emacs
-inside of nix-shell just to make it find out the necessary settings for
-building the project; `cabal-install` has already done that for us.
-
-If you want to do some quick-and-dirty hacking and don't want to bother setting
-up a `default.nix` and `shell.nix` file manually, then you can use the
-`--shell` flag offered by `cabal2nix` to have it generate a stand-alone
-`nix-shell` environment for you. With that feature, running
-```shell
-cabal2nix --shell . > shell.nix
-nix-shell --command "cabal configure"
-```
-is usually enough to set up a build environment for any given Haskell package.
-You can even use that generated file to run `nix-build`, too:
-```shell
-nix-build shell.nix
-```
-
-### How to build projects that depend on each other
-
-If you have multiple private Haskell packages that depend on each other, then
-you'll have to register those packages in the Nixpkgs set to make them visible
-for the dependency resolution performed by `callPackage`. First of all, change
-into each of your projects top-level directories and generate a `default.nix`
-file with `cabal2nix`:
-```shell
-cd ~/src/foo && cabal2nix . > default.nix
-cd ~/src/bar && cabal2nix . > default.nix
-```
-Then edit your `~/.config/nixpkgs/config.nix` file to register those builds in the
-default Haskell package set:
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    haskellPackages = super.haskellPackages.override {
-      overrides = self: super: {
-        foo = self.callPackage ../src/foo {};
-        bar = self.callPackage ../src/bar {};
-      };
-    };
-  };
-}
-```
-Once that's accomplished, `nix-env -f "<nixpkgs>" -qA haskellPackages` will
-show your packages like any other package from Hackage, and you can build them
-```shell
-nix-build "<nixpkgs>" -A haskellPackages.foo
-```
-or enter an interactive shell environment suitable for building them:
-```shell
-nix-shell "<nixpkgs>" -A haskellPackages.bar.env
-```
-
-## Miscellaneous Topics
-
-### How to build with profiling enabled
-
-Every Haskell package set takes a function called `overrides` that you can use
-to manipulate the package as much as you please. One useful application of this
-feature is to replace the default `mkDerivation` function with one that enables
-library profiling for all packages. To accomplish that add the following
-snippet to your `~/.config/nixpkgs/config.nix` file:
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    profiledHaskellPackages = self.haskellPackages.override {
-      overrides = self: super: {
-        mkDerivation = args: super.mkDerivation (args // {
-          enableLibraryProfiling = true;
-        });
-      };
-    };
-  };
-}
-```
-Then, replace instances of `haskellPackages` in the `cabal2nix`-generated
-`default.nix` or `shell.nix` files with `profiledHaskellPackages`.
-
-### How to override package versions in a compiler-specific package set
 
-Nixpkgs provides the latest version of
-[`ghc-events`](http://hackage.haskell.org/package/ghc-events), which is 0.4.4.0
-at the time of this writing. This is fine for users of GHC 7.10.x, but GHC
-7.8.4 cannot compile that binary. Now, one way to solve that problem is to
-register an older version of `ghc-events` in the 7.8.x-specific package set.
-The first step is to generate Nix build instructions with `cabal2nix`:
-```shell
-cabal2nix cabal://ghc-events-0.4.3.0 > ~/.nixpkgs/ghc-events-0.4.3.0.nix
-```
-Then add the override in `~/.config/nixpkgs/config.nix`:
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    haskell = super.haskell // {
-      packages = super.haskell.packages // {
-        ghc784 = super.haskell.packages.ghc784.override {
-          overrides = self: super: {
-            ghc-events = self.callPackage ./ghc-events-0.4.3.0.nix {};
-          };
-        };
-      };
-    };
-  };
-}
-```
-
-This code is a little crazy, no doubt, but it's necessary because the intuitive
-version
-```nix
-{ # ...
-
-  haskell.packages.ghc784 = super.haskell.packages.ghc784.override {
-    overrides = self: super: {
-      ghc-events = self.callPackage ./ghc-events-0.4.3.0.nix {};
-    };
-  };
-}
-```
-doesn't do what we want it to: that code replaces the `haskell` package set in
-Nixpkgs with one that contains only one entry,`packages`, which contains only
-one entry `ghc784`. This override loses the `haskell.compiler` set, and it
-loses the `haskell.packages.ghcXYZ` sets for all compilers but GHC 7.8.4. To
-avoid that problem, we have to perform the convoluted little dance from above,
-iterating over each step in hierarchy.
-
-Once it's accomplished, however, we can install a variant of `ghc-events`
-that's compiled with GHC 7.8.4:
-```shell
-nix-env -f "<nixpkgs>" -iA haskell.packages.ghc784.ghc-events
-```
-Unfortunately, it turns out that this build fails again while executing the
-test suite! Apparently, the release archive on Hackage is missing some data
-files that the test suite requires, so we cannot run it. We accomplish that by
-re-generating the Nix expression with the `--no-check` flag:
-```shell
-cabal2nix --no-check cabal://ghc-events-0.4.3.0 > ~/.nixpkgs/ghc-events-0.4.3.0.nix
-```
-Now the builds succeeds.
-
-Of course, in the concrete example of `ghc-events` this whole exercise is not
-an ideal solution, because `ghc-events` can analyze the output emitted by any
-version of GHC later than 6.12 regardless of the compiler version that was used
-to build the `ghc-events` executable, so strictly speaking there's no reason to
-prefer one built with GHC 7.8.x in the first place. However, for users who
-cannot use GHC 7.10.x at all for some reason, the approach of downgrading to an
-older version might be useful.
-
-### How to override packages in all compiler-specific package sets
-
-In the previous section we learned how to override a package in a single
-compiler-specific package set. You may have some overrides defined that you want
-to use across multiple package sets. To accomplish this you could use the
-technique that we learned in the previous section by repeating the overrides for
-all the compiler-specific package sets. For example:
-
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    haskell = super.haskell // {
-      packages = super.haskell.packages // {
-        ghc784 = super.haskell.packages.ghc784.override {
-          overrides = self: super: {
-            my-package = ...;
-            my-other-package = ...;
-          };
-        };
-        ghc822 = super.haskell.packages.ghc784.override {
-          overrides = self: super: {
-            my-package = ...;
-            my-other-package = ...;
-          };
-        };
-        ...
-      };
-    };
-  };
-}
-```
-
-However there's a more convenient way to override all compiler-specific package
-sets at once:
-
-```nix
-{
-  packageOverrides = super: let self = super.pkgs; in
-  {
-    haskell = super.haskell // {
-      packageOverrides = self: super: {
-        my-package = ...;
-        my-other-package = ...;
-      };
-    };
-  };
-}
-```
-
-### How to specify source overrides for your Haskell package
-
-When starting a Haskell project you can use `developPackage`
-to define a derivation for your package at the `root` path
-as well as source override versions for Hackage packages, like so:
-
-```nix
-# default.nix
-{ compilerVersion ? "ghc842" }:
-let
-  # pinning nixpkgs using new Nix 2.0 builtin `fetchGit`
-  pkgs = import (fetchGit (import ./version.nix)) { };
-  compiler = pkgs.haskell.packages."${compilerVersion}";
-  pkg = compiler.developPackage {
-    root = ./.;
-    source-overrides = {
-      # Let's say the GHC 8.4.2 haskellPackages uses 1.6.0.0 and your test suite is incompatible with >= 1.6.0.0
-      HUnit = "1.5.0.0";
-    };
-  };
-in pkg
-```
-
-This could be used in place of a simplified `stack.yaml` defining a Nix
-derivation for your Haskell package.
-
-As you can see this allows you to specify only the source version found on
-Hackage and nixpkgs will take care of the rest.
-
-You can also specify `buildInputs` for your Haskell derivation for packages
-that directly depend on external libraries like so:
-
-```nix
-# default.nix
-{ compilerVersion ? "ghc842" }:
-let
-  # pinning nixpkgs using new Nix 2.0 builtin `fetchGit`
-  pkgs = import (fetchGit (import ./version.nix)) { };
-  compiler = pkgs.haskell.packages."${compilerVersion}";
-  pkg = compiler.developPackage {
-    root = ./.;
-    source-overrides = {
-      HUnit = "1.5.0.0"; # Let's say the GHC 8.4.2 haskellPackages uses 1.6.0.0 and your test suite is incompatible with >= 1.6.0.0
-    };
-  };
-  # in case your package source depends on any libraries directly, not just transitively.
-  buildInputs = [ zlib ];
-in pkg.overrideAttrs(attrs: {
-  buildInputs = attrs.buildInputs ++ buildInputs;
-})
-```
-
-Notice that you will need to override (via `overrideAttrs` or similar) the
-derivation returned by the `developPackage` Nix lambda as there is no `buildInputs`
-named argument you can pass directly into the `developPackage` lambda.
-
-### How to recover from GHC's infamous non-deterministic library ID bug
-
-GHC and distributed build farms don't get along well:
-
-  - https://ghc.haskell.org/trac/ghc/ticket/4012
-
-When you see an error like this one
-```
-package foo-0.7.1.0 is broken due to missing package
-text-1.2.0.4-98506efb1b9ada233bb5c2b2db516d91
-```
-then you have to download and re-install `foo` and all its dependents from
-scratch:
-```shell
-nix-store -q --referrers /nix/store/*-haskell-text-1.2.0.4 \
-  | xargs -L 1 nix-store --repair-path
-```
-
-If you're using additional Hydra servers other than `hydra.nixos.org`, then it
-might be necessary to purge the local caches that store data from those
-machines to disable these binary channels for the duration of the previous
-command, i.e. by running:
-```shell
-rm ~/.cache/nix/binary-cache*.sqlite
-```
-
-### Builds on Darwin fail with `math.h` not found
-
-Users of GHC on Darwin have occasionally reported that builds fail, because the
-compiler complains about a missing include file:
-```
-fatal error: 'math.h' file not found
-```
-The issue has been discussed at length in [ticket
-6390](https://github.com/NixOS/nixpkgs/issues/6390), and so far no good
-solution has been proposed. As a work-around, users who run into this problem
-can configure the environment variables
-```shell
-export NIX_CFLAGS_COMPILE="-idirafter /usr/include"
-export NIX_CFLAGS_LINK="-L/usr/lib"
-```
-in their `~/.bashrc` file to avoid the compiler error.
-
-### Builds using Stack complain about missing system libraries
-
-```
---  While building package zlib-0.5.4.2 using:
-  runhaskell -package=Cabal-1.22.4.0 -clear-package-db [... lots of flags ...]
-Process exited with code: ExitFailure 1
-Logs have been written to: /home/foo/src/stack-ide/.stack-work/logs/zlib-0.5.4.2.log
-
-Configuring zlib-0.5.4.2...
-Setup.hs: Missing dependency on a foreign library:
-* Missing (or bad) header file: zlib.h
-This problem can usually be solved by installing the system package that
-provides this library (you may need the "-dev" version). If the library is
-already installed but in a non-standard location then you can use the flags
---extra-include-dirs= and --extra-lib-dirs= to specify where it is.
-If the header file does exist, it may contain errors that are caught by the C
-compiler at the preprocessing stage. In this case you can re-run configure
-with the verbosity flag -v3 to see the error messages.
-```
-
-When you run the build inside of the nix-shell environment, the system
-is configured to find `libz.so` without any special flags -- the compiler
-and linker "just know" how to find it. Consequently, Cabal won't record
-any search paths for `libz.so` in the package description, which means
-that the package works fine inside of nix-shell, but once you leave the
-shell the shared object can no longer be found. That issue is by no
-means specific to Stack: you'll have that problem with any other
-Haskell package that's built inside of nix-shell but run outside of that
-environment.
-
-You can remedy this issue in several ways. The easiest is to add a `nix` section
-to the `stack.yaml` like the following:
-```yaml
-nix:
-  enable: true
-  packages: [ zlib ]
-```
-
-Stack's Nix support knows to add `${zlib.out}/lib` and `${zlib.dev}/include`
-as an `--extra-lib-dirs` and `extra-include-dirs`, respectively.
-Alternatively, you can achieve the same effect by hand. First of all, run
-```
-$ nix-build --no-out-link "<nixpkgs>" -A zlib
-/nix/store/alsvwzkiw4b7ip38l4nlfjijdvg3fvzn-zlib-1.2.8
-```
-to find out the store path of the system's zlib library. Now, you can
-
-  1. add that path (plus a "/lib" suffix) to your `$LD_LIBRARY_PATH`
-    environment variable to make sure your system linker finds `libz.so`
-    automatically. It's no pretty solution, but it will work.
-
-  2. As a variant of (1), you can also install any number of system
-    libraries into your user's profile (or some other profile) and point
-    `$LD_LIBRARY_PATH` to that profile instead, so that you don't have to
-    list dozens of those store paths all over the place.
-
-  3. The solution I prefer is to call stack with an appropriate
-    --extra-lib-dirs flag like so:
-    ```shell
-    stack --extra-lib-dirs=/nix/store/alsvwzkiw4b7ip38l4nlfjijdvg3fvzn-zlib-1.2.8/lib build
-    ```
-
-Typically, you'll need `--extra-include-dirs` as well. It's possible
-to add those flag to the project's `stack.yaml` or your user's
-global `~/.stack/global/stack.yaml` file so that you don't have to
-specify them manually every time. But again, you're likely better off
-using Stack's Nix support instead.
-
-The same thing applies to `cabal configure`, of course, if you're
-building with `cabal-install` instead of Stack.
-
-### Creating statically linked binaries
-
-There are two levels of static linking. The first option is to configure the
-build with the Cabal flag `--disable-executable-dynamic`. In Nix expressions,
-this can be achieved by setting the attribute:
-```
-enableSharedExecutables = false;
-```
-That gives you a binary with statically linked Haskell libraries and
-dynamically linked system libraries.
-
-To link both Haskell libraries and system libraries statically, the additional
-flags `--ghc-option=-optl=-static --ghc-option=-optl=-pthread` need to be used.
-In Nix, this is accomplished with:
-```
-configureFlags = [ "--ghc-option=-optl=-static" "--ghc-option=-optl=-pthread" ];
-```
-
-It's important to realize, however, that most system libraries in Nix are
-built as shared libraries only, i.e. there is just no static library
-available that Cabal could link!
-
-### Building GHC with integer-simple
-
-By default GHC implements the Integer type using the
-[GNU Multiple Precision Arithmetic (GMP) library](https://gmplib.org/).
-The implementation can be found in the
-[integer-gmp](http://hackage.haskell.org/package/integer-gmp) package.
-
-A potential problem with this is that GMP is licensed under the
-[GNU Lesser General Public License (LGPL)](https://www.gnu.org/copyleft/lesser.html),
-a kind of "copyleft" license. According to the terms of the LGPL, paragraph 5,
-you may distribute a program that is designed to be compiled and dynamically
-linked with the library under the terms of your choice (i.e., commercially) but
-if your program incorporates portions of the library, if it is linked
-statically, then your program is a "derivative"--a "work based on the
-library"--and according to paragraph 2, section c, you "must cause the whole of
-the work to be licensed" under the terms of the LGPL (including for free).
-
-The LGPL licensing for GMP is a problem for the overall licensing of binary
-programs compiled with GHC because most distributions (and builds) of GHC use
-static libraries. (Dynamic libraries are currently distributed only for macOS.)
-The LGPL licensing situation may be worse: even though
-[The Glasgow Haskell Compiler License](https://www.haskell.org/ghc/license)
-is essentially a "free software" license (BSD3), according to
-paragraph 2 of the LGPL, GHC must be distributed under the terms of the LGPL!
-
-To work around these problems GHC can be build with a slower but LGPL-free
-alternative implementation for Integer called
-[integer-simple](http://hackage.haskell.org/package/integer-simple).
-
-To get a GHC compiler build with `integer-simple` instead of `integer-gmp` use
-the attribute: `haskell.compiler.integer-simple."${ghcVersion}"`.
-For example:
-```
-$ nix-build -E '(import <nixpkgs> {}).haskell.compiler.integer-simple.ghc802'
-...
-$ result/bin/ghc-pkg list | grep integer
-    integer-simple-0.1.1.1
-```
-The following command displays the complete list of GHC compilers build with `integer-simple`:
-```
-$ nix-env -f "<nixpkgs>" -qaP -A haskell.compiler.integer-simple
-haskell.compiler.integer-simple.ghc7102  ghc-7.10.2
-haskell.compiler.integer-simple.ghc7103  ghc-7.10.3
-haskell.compiler.integer-simple.ghc722   ghc-7.2.2
-haskell.compiler.integer-simple.ghc742   ghc-7.4.2
-haskell.compiler.integer-simple.ghc783   ghc-7.8.3
-haskell.compiler.integer-simple.ghc784   ghc-7.8.4
-haskell.compiler.integer-simple.ghc801   ghc-8.0.1
-haskell.compiler.integer-simple.ghc802   ghc-8.0.2
-haskell.compiler.integer-simple.ghcHEAD  ghc-8.1.20170106
-```
-
-To get a package set supporting `integer-simple` use the attribute:
-`haskell.packages.integer-simple."${ghcVersion}"`. For example
-use the following to get the `scientific` package build with `integer-simple`:
-```shell
-nix-build -A haskell.packages.integer-simple.ghc802.scientific
-```
-
-### Quality assurance
-
-The `haskell.lib` library includes a number of functions for checking for
-various imperfections in Haskell packages. It's useful to apply these functions
-to your own Haskell packages and integrate that in a Continuous Integration
-server like [hydra](https://nixos.org/hydra/) to assure your packages maintain a
-minimum level of quality. This section discusses some of these functions.
-
-#### failOnAllWarnings
-
-Applying `haskell.lib.failOnAllWarnings` to a Haskell package enables the
-`-Wall` and `-Werror` GHC options to turn all warnings into build failures.
-
-#### buildStrictly
-
-Applying `haskell.lib.buildStrictly` to a Haskell package calls
-`failOnAllWarnings` on the given package to turn all warnings into build
-failures. Additionally the source of your package is gotten from first invoking
-`cabal sdist` to ensure all needed files are listed in the Cabal file.
-
-#### checkUnusedPackages
-
-Applying `haskell.lib.checkUnusedPackages` to a Haskell package invokes
-the [packunused](http://hackage.haskell.org/package/packunused) tool on the
-package. `packunused` complains when it finds packages listed as build-depends
-in the Cabal file which are redundant. For example:
-
-```
-$ nix-build -E 'let pkgs = import <nixpkgs> {}; in pkgs.haskell.lib.checkUnusedPackages {} pkgs.haskellPackages.scientific'
-these derivations will be built:
-  /nix/store/3lc51cxj2j57y3zfpq5i69qbzjpvyci1-scientific-0.3.5.1.drv
-...
-detected package components
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
- - library
- - testsuite(s): test-scientific
- - benchmark(s): bench-scientific*
-
-(component names suffixed with '*' are not configured to be built)
-
-library
-~~~~~~~
-
-The following package dependencies seem redundant:
-
- - ghc-prim-0.5.0.0
-
-testsuite(test-scientific)
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-no redundant packages dependencies found
-
-builder for ‘/nix/store/3lc51cxj2j57y3zfpq5i69qbzjpvyci1-scientific-0.3.5.1.drv’ failed with exit code 1
-error: build of ‘/nix/store/3lc51cxj2j57y3zfpq5i69qbzjpvyci1-scientific-0.3.5.1.drv’ failed
-```
-
-As you can see, `packunused` finds out that although the testsuite component has
-no redundant dependencies the library component of `scientific-0.3.5.1` depends
-on `ghc-prim` which is unused in the library.
-
-### Using hackage2nix with nixpkgs
-
-Hackage package derivations are found in the
-[`hackage-packages.nix`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/hackage-packages.nix)
-file within `nixpkgs` and are used as the initial package set for
-`haskellPackages`. The `hackage-packages.nix` file is not meant to be edited
-by hand, but rather autogenerated by [`hackage2nix`](https://github.com/NixOS/cabal2nix/tree/master/hackage2nix),
-which by default uses the [`configuration-hackage2nix.yaml`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/configuration-hackage2nix.yaml)
-file to generate all the derivations.
-
-To modify the contents `configuration-hackage2nix.yaml`, follow the
-instructions on [`hackage2nix`](https://github.com/NixOS/cabal2nix/tree/master/hackage2nix).
-
-## Other resources
-
-  - The Youtube video [Nix Loves Haskell](https://www.youtube.com/watch?v=BsBhi_r-OeE)
-    provides an introduction into Haskell NG aimed at beginners. The slides are
-    available at http://cryp.to/nixos-meetup-3-slides.pdf and also -- in a form
-    ready for cut & paste -- at
-    https://github.com/NixOS/cabal2nix/blob/master/doc/nixos-meetup-3-slides.md.
-
-  - Another Youtube video is [Escaping Cabal Hell with Nix](https://www.youtube.com/watch?v=mQd3s57n_2Y),
-    which discusses the subject of Haskell development with Nix but also provides
-    a basic introduction to Nix as well, i.e. it's suitable for viewers with
-    almost no prior Nix experience.
-
-  - Oliver Charles wrote a very nice [Tutorial how to develop Haskell packages with Nix](http://wiki.ocharles.org.uk/Nix).
-
-  - The *Journey into the Haskell NG infrastructure* series of postings
-    describe the new Haskell infrastructure in great detail:
-
-      - [Part 1](https://nixos.org/nix-dev/2015-January/015591.html)
-        explains the differences between the old and the new code and gives
-        instructions how to migrate to the new setup.
-
-      - [Part 2](https://nixos.org/nix-dev/2015-January/015608.html)
-        looks in-depth at how to tweak and configure your setup by means of
-        overrides.
+# Haskell
 
-      - [Part 3](https://nixos.org/nix-dev/2015-April/016912.html)
-        describes the infrastructure that keeps the Haskell package set in Nixpkgs
-        up-to-date.
+The documentation for the Haskell infrastructure is published at
+<https://haskell4nix.readthedocs.io/>. The source code for that
+site lives in the `doc/` sub-directory of the
+[`cabal2nix` Git repository](https://github.com/NixOS/cabal2nix)
+and changes can be submitted there.
diff --git a/doc/languages-frameworks/index.xml b/doc/languages-frameworks/index.xml
index 728a38c264a3c..3366108cd938e 100644
--- a/doc/languages-frameworks/index.xml
+++ b/doc/languages-frameworks/index.xml
@@ -19,6 +19,7 @@
  <xi:include href="ios.section.xml" />
  <xi:include href="java.xml" />
  <xi:include href="lua.section.xml" />
+ <xi:include href="maven.section.xml" />
  <xi:include href="node.section.xml" />
  <xi:include href="ocaml.xml" />
  <xi:include href="perl.xml" />
diff --git a/doc/languages-frameworks/java.xml b/doc/languages-frameworks/java.xml
index bf0fc48839223..881d492b5bff7 100644
--- a/doc/languages-frameworks/java.xml
+++ b/doc/languages-frameworks/java.xml
@@ -32,7 +32,7 @@ nativeBuildInputs = [ jdk ];
  </para>
 
  <para>
-  If your Java package provides a program, you need to generate a wrapper script to run it using the OpenJRE. You can use <literal>makeWrapper</literal> for this:
+  If your Java package provides a program, you need to generate a wrapper script to run it using a JRE. You can use <literal>makeWrapper</literal> for this:
 <programlisting>
 nativeBuildInputs = [ makeWrapper ];
 
@@ -43,7 +43,21 @@ installPhase =
       --add-flags "-cp $out/share/java/foo.jar org.foo.Main"
   '';
 </programlisting>
-  Note the use of <literal>jre</literal>, which is the part of the OpenJDK package that contains the Java Runtime Environment. By using <literal>${jre}/bin/java</literal> instead of <literal>${jdk}/bin/java</literal>, you prevent your package from depending on the JDK at runtime.
+Since the introduction of the Java Platform Module System in Java 9, Java distributions typically no longer ship with a general-purpose JRE: instead, they allow generating a JRE with only the modules required for your application(s). Because we can't predict what modules will be needed on a general-purpose system, the default <package>jre</package> package is the full JDK. When building a minimal system/image, you can override the <literal>modules</literal> parameter on <literal>jre_minimal</literal> to build a JRE with only the modules relevant for you:
+<programlisting>
+let
+  my_jre = pkgs.jre_minimal.override {
+    modules = [
+      # The modules used by 'something' and 'other' combined:
+      "java.base"
+      "java.logging"
+    ];
+  };
+  something = (pkgs.something.override { jre = my_jre; });
+  other = (pkgs.other.override { jre = my_jre; });
+in
+  ...
+</programlisting>
  </para>
 
  <para>
diff --git a/doc/languages-frameworks/maven.section.md b/doc/languages-frameworks/maven.section.md
new file mode 100644
index 0000000000000..fe183e7ba3cca
--- /dev/null
+++ b/doc/languages-frameworks/maven.section.md
@@ -0,0 +1,354 @@
+---
+title: Maven
+author: Farid Zakaria
+date: 2020-10-15
+---
+
+# Maven
+
+Maven is a well-known build tool for the Java ecosystem however it has some challenges when integrating into the Nix build system.
+
+The following provides a list of common patterns with how to package a Maven project (or any JVM language that can export to Maven) as a Nix package.
+
+For the purposes of this example let's consider a very basic Maven project with the following `pom.xml` with a single dependency on [emoji-java](https://github.com/vdurmont/emoji-java).
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>io.github.fzakaria</groupId>
+  <artifactId>maven-demo</artifactId>
+  <version>1.0</version>
+  <packaging>jar</packaging>
+  <name>NixOS Maven Demo</name>
+
+  <dependencies>
+    <dependency>
+        <groupId>com.vdurmont</groupId>
+        <artifactId>emoji-java</artifactId>
+        <version>5.1.1</version>
+      </dependency>
+  </dependencies>
+</project>
+```
+
+Our main class file will be very simple:
+
+```java
+import com.vdurmont.emoji.EmojiParser;
+
+public class Main {
+  public static void main(String[] args) {
+    String str = "NixOS :grinning: is super cool :smiley:!";
+    String result = EmojiParser.parseToUnicode(str);
+    System.out.println(result);
+  }
+}
+```
+
+You find this demo project at https://github.com/fzakaria/nixos-maven-example
+
+## Solving for dependencies
+
+### buildMaven with NixOS/mvn2nix-maven-plugin
+
+> ⚠️ Although `buildMaven` is the "blessed" way within nixpkgs, as of 2020, it hasn't seen much activity in quite a while.
+
+`buildMaven` is an alternative method that tries to follow similar patterns of other programming languages by generating a lock file. It relies on the maven plugin [mvn2nix-maven-plugin](https://github.com/NixOS/mvn2nix-maven-plugin).
+
+First you generate a `project-info.json` file using the maven plugin.
+
+> This should be executed in the project's source repository or be told which `pom.xml` to execute with.
+
+```bash
+# run this step within the project's source repository
+❯ mvn org.nixos.mvn2nix:mvn2nix-maven-plugin:mvn2nix
+
+❯ cat project-info.json | jq | head
+{
+  "project": {
+    "artifactId": "maven-demo",
+    "groupId": "org.nixos",
+    "version": "1.0",
+    "classifier": "",
+    "extension": "jar",
+    "dependencies": [
+      {
+        "artifactId": "maven-resources-plugin",
+```
+
+This file is then given to the `buildMaven` function, and it returns 2 attributes.
+
+**`repo`**:
+    A Maven repository that is a symlink farm of all the dependencies found in the `project-info.json`
+
+
+**`build`**:
+    A simple derivation that runs through `mvn compile` & `mvn package` to build the JAR. You may use this as inspiration for more complicated derivations.
+
+Here is an [example](https://github.com/fzakaria/nixos-maven-example/blob/main/build-maven-repository.nix) of building the Maven repository
+```nix
+{ pkgs ? import <nixpkgs> { } }:
+with pkgs;
+(buildMaven ./project-info.json).repo
+```
+
+The benefit over the _double invocation_ as we will see below, is that the _/nix/store_ entry is a _linkFarm_ of every package, so that changes to your dependency set doesn't involve downloading everything from scratch.
+
+```bash
+❯ tree $(nix-build --no-out-link build-maven-repository.nix) | head
+/nix/store/g87va52nkc8jzbmi1aqdcf2f109r4dvn-maven-repository
+├── antlr
+│   └── antlr
+│       └── 2.7.2
+│           ├── antlr-2.7.2.jar -> /nix/store/d027c8f2cnmj5yrynpbq2s6wmc9cb559-antlr-2.7.2.jar
+│           └── antlr-2.7.2.pom -> /nix/store/mv42fc5gizl8h5g5vpywz1nfiynmzgp2-antlr-2.7.2.pom
+├── avalon-framework
+│   └── avalon-framework
+│       └── 4.1.3
+│           ├── avalon-framework-4.1.3.jar -> /nix/store/iv5fp3955w3nq28ff9xfz86wvxbiw6n9-avalon-framework-4.1.3.jar
+```
+### Double Invocation
+
+> ⚠️ This pattern is the simplest but may cause unnecessary rebuilds due to the output hash changing.
+
+The double invocation is a _simple_ way to get around the problem that `nix-build` may be sandboxed and have no Internet connectivity.
+
+It treats the entire Maven repository as a single source to be downloaded, relying on Maven's dependency resolution to satisfy the output hash. This is similar to fetchers like `fetchgit`, except it has to run a Maven build to determine what to download.
+
+The first step will be to build the Maven project as a fixed-output derivation in order to collect the Maven repository -- below is an [example](https://github.com/fzakaria/nixos-maven-example/blob/main/double-invocation-repository.nix).
+
+> Traditionally the Maven repository is at `~/.m2/repository`. We will override this to be the `$out` directory.
+
+```nix
+{ stdenv, maven }:
+stdenv.mkDerivation {
+  name = "maven-repository";
+  buildInputs = [ maven ];
+  src = ./.; # or fetchFromGitHub, cleanSourceWith, etc
+  buildPhase = ''
+    mvn package -Dmaven.repo.local=$out
+  '';
+
+  # keep only *.{pom,jar,sha1,nbm} and delete all ephemeral files with lastModified timestamps inside
+  installPhase = ''
+    find $out -type f \
+      -name \*.lastUpdated -or \
+      -name resolver-status.properties -or \
+      -name _remote.repositories \
+      -delete
+  '';
+
+  # don't do any fixup
+  dontFixup = true;
+  outputHashAlgo = "sha256";
+  outputHashMode = "recursive";
+  # replace this with the correct SHA256
+  outputHash = stdenv.lib.fakeSha256;
+}
+```
+
+The build will fail, and tell you the expected `outputHash` to place. When you've set the hash, the build will return with a `/nix/store` entry whose contents are the full Maven repository.
+
+> Some additional files are deleted that would cause the output hash to change potentially on subsequent runs.
+
+```bash
+❯ tree $(nix-build --no-out-link double-invocation-repository.nix) | head
+/nix/store/8kicxzp98j68xyi9gl6jda67hp3c54fq-maven-repository
+├── backport-util-concurrent
+│   └── backport-util-concurrent
+│       └── 3.1
+│           ├── backport-util-concurrent-3.1.pom
+│           └── backport-util-concurrent-3.1.pom.sha1
+├── classworlds
+│   └── classworlds
+│       ├── 1.1
+│       │   ├── classworlds-1.1.jar
+```
+
+If your package uses _SNAPSHOT_ dependencies or _version ranges_; there is a strong likelihood that over-time your output hash will change since the resolved dependencies may change. Hence this method is less recommended then using `buildMaven`.
+
+## Building a JAR
+
+Regardless of which strategy is chosen above, the step to build the derivation is the same.
+
+```nix
+{ stdenv, lib, maven, callPackage }:
+# pick a repository derivation, here we will use buildMaven
+let repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+  '';
+}
+```
+
+> We place the library in `$out/share/java` since JDK package has a _stdenv setup hook_ that adds any JARs in the `share/java` directories of the build inputs to the CLASSPATH environment.
+
+```bash
+❯ tree $(nix-build --no-out-link build-jar.nix)
+/nix/store/7jw3xdfagkc2vw8wrsdv68qpsnrxgvky-maven-demo-1.0
+└── share
+    └── java
+        └── maven-demo-1.0.jar
+
+2 directories, 1 file
+```
+
+## Runnable JAR
+
+The previous example builds a `jar` file but that's not a file one can run.
+
+You need to use it with `java -jar $out/share/java/output.jar` and make sure to provide the required dependencies on the classpath.
+
+The following explains how to use `makeWrapper` in order to make the derivation produce an executable that will run the JAR file you created.
+
+We will use the same repository we built above (either _double invocation_ or _buildMaven_) to setup a CLASSPATH for our JAR.
+
+The following two methods are more suited to Nix then building an [UberJar](https://imagej.net/Uber-JAR) which may be the more traditional approach.
+
+### CLASSPATH
+
+> This is ideal if you are providing a derivation for _nixpkgs_ and don't want to patch the project's `pom.xml`.
+
+We will read the Maven repository and flatten it to a single list. This list will then be concatenated with the _CLASSPATH_ separator to create the full classpath.
+
+We make sure to provide this classpath to the `makeWrapper`.
+
+```nix
+{ stdenv, lib, maven, callPackage, makeWrapper, jre }:
+let
+  repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball
+    "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven makeWrapper ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+
+    classpath=$(find ${repository} -name "*.jar" -printf ':%h/%f');
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+    # create a wrapper that will automatically set the classpath
+    # this should be the paths from the dependency derivation
+    makeWrapper ${jre}/bin/java $out/bin/${pname} \
+          --add-flags "-classpath $out/share/java/${pname}-${version}.jar:''${classpath#:}" \
+          --add-flags "Main"
+  '';
+}
+```
+
+### MANIFEST file via Maven Plugin
+
+> This is ideal if you are the project owner and want to change your `pom.xml` to set the CLASSPATH within it.
+
+Augment the `pom.xml` to create a JAR with the following manifest:
+```xml
+<build>
+  <plugins>
+    <plugin>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+            <archive>
+                <manifest>
+                    <addClasspath>true</addClasspath>
+                    <classpathPrefix>../../repository/</classpathPrefix>
+                    <classpathLayoutType>repository</classpathLayoutType>
+                    <mainClass>Main</mainClass>
+                </manifest>
+                <manifestEntries>
+                    <Class-Path>.</Class-Path>
+                </manifestEntries>
+            </archive>
+        </configuration>
+    </plugin>
+  </plugins>
+</build>
+```
+
+The above plugin instructs the JAR to look for the necessary dependencies in the `lib/` relative folder. The layout of the folder is also in the _maven repository_ style.
+
+```bash
+❯ unzip -q -c $(nix-build --no-out-link runnable-jar.nix)/share/java/maven-demo-1.0.jar META-INF/MANIFEST.MF
+
+Manifest-Version: 1.0
+Archiver-Version: Plexus Archiver
+Built-By: nixbld
+Class-Path: . ../../repository/com/vdurmont/emoji-java/5.1.1/emoji-jav
+ a-5.1.1.jar ../../repository/org/json/json/20170516/json-20170516.jar
+Created-By: Apache Maven 3.6.3
+Build-Jdk: 1.8.0_265
+Main-Class: Main
+```
+
+We will modify the derivation above to add a symlink to our repository so that it's accessible to our JAR during the `installPhase`.
+
+```nix
+{ stdenv, lib, maven, callPackage, makeWrapper, jre }:
+# pick a repository derivation, here we will use buildMaven
+let repository = callPackage ./build-maven-repository.nix { };
+in stdenv.mkDerivation rec {
+  pname = "maven-demo";
+  version = "1.0";
+
+  src = builtins.fetchTarball
+    "https://github.com/fzakaria/nixos-maven-example/archive/main.tar.gz";
+  buildInputs = [ maven makeWrapper ];
+
+  buildPhase = ''
+    echo "Using repository ${repository}"
+    mvn --offline -Dmaven.repo.local=${repository} package;
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+
+    # create a symbolic link for the repository directory
+    ln -s ${repository} $out/repository
+
+    install -Dm644 target/${pname}-${version}.jar $out/share/java
+    # create a wrapper that will automatically set the classpath
+    # this should be the paths from the dependency derivation
+    makeWrapper ${jre}/bin/java $out/bin/${pname} \
+          --add-flags "-jar $out/share/java/${pname}-${version}.jar"
+  '';
+}
+```
+
+> Our script produces a dependency on `jre` rather than `jdk` to restrict the runtime closure necessary to run the application.
+
+This will give you an executable shell-script that launches your JAR with all the dependencies available.
+
+```bash
+❯ tree $(nix-build --no-out-link runnable-jar.nix)
+/nix/store/8d4c3ibw8ynsn01ibhyqmc1zhzz75s26-maven-demo-1.0
+├── bin
+│   └── maven-demo
+├── repository -> /nix/store/g87va52nkc8jzbmi1aqdcf2f109r4dvn-maven-repository
+└── share
+    └── java
+        └── maven-demo-1.0.jar
+
+❯ $(nix-build --no-out-link --option tarball-ttl 1 runnable-jar.nix)/bin/maven-demo
+NixOS 😀 is super cool 😃!
+```
diff --git a/doc/languages-frameworks/python.section.md b/doc/languages-frameworks/python.section.md
index e2d9172919ef5..59f7389b9ad3c 100644
--- a/doc/languages-frameworks/python.section.md
+++ b/doc/languages-frameworks/python.section.md
@@ -755,8 +755,8 @@ and in this case the `python38` interpreter is automatically used.
 
 ### Interpreters
 
-Versions 2.7, 3.6, 3.7 and 3.8 of the CPython interpreter are available as
-respectively `python27`, `python36`, `python37` and `python38`. The
+Versions 2.7, 3.6, 3.7, 3.8 and 3.9 of the CPython interpreter are available as
+respectively `python27`, `python36`, `python37`, `python38` and `python39`. The
 aliases `python2` and `python3` correspond to respectively `python27` and
 `python38`. The default interpreter, `python`, maps to `python2`. The PyPy
 interpreters compatible with Python 2.7 and 3 are available as `pypy27` and
diff --git a/doc/languages-frameworks/vim.section.md b/doc/languages-frameworks/vim.section.md
index 8e4826232e1ab..84ad567e8c212 100644
--- a/doc/languages-frameworks/vim.section.md
+++ b/doc/languages-frameworks/vim.section.md
@@ -265,6 +265,20 @@ To add a new plugin, run `./update.py --add "[owner]/[name]"`. **NOTE**: This sc
 
 Finally, there are some plugins that are also packaged in nodePackages because they have Javascript-related build steps, such as running webpack. Those plugins are not listed in `vim-plugin-names` or managed by `update.py` at all, and are included separately in `overrides.nix`. Currently, all these plugins are related to the `coc.nvim` ecosystem of Language Server Protocol integration with vim/neovim.
 
+## Updating plugins in nixpkgs
+
+Run the update script with a GitHub API token that has at least `public_repo` access. Running the script without the token is likely to result in rate-limiting (429 errors). For steps on creating an API token, please refer to [GitHub's token documentation](https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token).
+
+```sh
+GITHUB_API_TOKEN=my_token ./pkgs/misc/vim-plugins/update.py
+```
+
+Alternatively, set the number of processes to a lower count to avoid rate-limiting.
+
+```sh
+./pkgs/misc/vim-plugins/update.py --proc 1
+```
+
 ## Important repositories
 
 - [vim-pi](https://bitbucket.org/vimcommunity/vim-pi) is a plugin repository
diff --git a/doc/stdenv/stdenv.xml b/doc/stdenv/stdenv.xml
index f97c2a145af52..46ee97927eac3 100644
--- a/doc/stdenv/stdenv.xml
+++ b/doc/stdenv/stdenv.xml
@@ -475,9 +475,12 @@ passthru.updateScript = writeScript "update-zoom-us" ''
 <programlisting>
 passthru.updateScript = [ ../../update.sh pname "--requested-release=unstable" ];
 </programlisting>
-     </para>
-     <para>
-      The script will be usually run from the root of the Nixpkgs repository but you should not rely on that. Also note that the update scripts will be run in parallel by default; you should avoid running <command>git commit</command> or any other commands that cannot handle that.
+      The script will be run with <varname>UPDATE_NIX_ATTR_PATH</varname> environment variable set to the attribute path it is supposed to update.
+      <note>
+       <para>
+        The script will be usually run from the root of the Nixpkgs repository but you should not rely on that. Also note that the update scripts will be run in parallel by default; you should avoid running <command>git commit</command> or any other commands that cannot handle that.
+       </para>
+      </note>
      </para>
      <para>
       For information about how to run the updates, execute <command>nix-shell maintainers/scripts/update.nix</command>.
@@ -1636,10 +1639,6 @@ substitute ./foo.in ./foo.out \
     --subst-var someVar
 </programlisting>
      </para>
-     <para>
-      <function>substitute</function> is implemented using the <command
-      xlink:href="http://replace.richardlloyd.org.uk/">replace</command> command. Unlike with the <command>sed</command> command, you don’t have to worry about escaping special characters. It supports performing substitutions on binary files (such as executables), though there you’ll probably want to make sure that the replacement string is as long as the replaced string.
-     </para>
     </listitem>
    </varlistentry>
    <varlistentry xml:id='fun-substituteInPlace'>
@@ -1836,6 +1835,19 @@ addEnvHooks "$hostOffset" myBashFunction
     </varlistentry>
     <varlistentry>
      <term>
+      <literal>move-systemd-user-units.sh</literal>
+     </term>
+     <listitem>
+      <para>
+       This setup hook moves any systemd user units installed in the lib
+       subdirectory into share. In addition, a link is provided from share to
+       lib for compatibility. This is needed for systemd to find user services
+       when installed into the user profile.
+      </para>
+     </listitem>
+    </varlistentry>
+    <varlistentry>
+     <term>
       <literal>set-source-date-epoch-to-latest.sh</literal>
      </term>
      <listitem>
@@ -2058,7 +2070,7 @@ nativeBuildInputs = [ breakpointHook ];
        The <literal>installManPage</literal> function takes one or more paths to manpages to install. The manpages must have a section suffix, and may optionally be compressed (with <literal>.gz</literal> suffix). This function will place them into the correct directory.
       </para>
       <para>
-       The <literal>installShellCompletion</literal> function takes one or more paths to shell completion files. By default it will autodetect the shell type from the completion file extension, but you may also specify it by passing one of <literal>--bash</literal>, <literal>--fish</literal>, or <literal>--zsh</literal>. These flags apply to all paths listed after them (up until another shell flag is given). Each path may also have a custom installation name provided by providing a flag <literal>--name NAME</literal> before the path. If this flag is not provided, zsh completions will be renamed automatically such that <literal>foobar.zsh</literal> becomes <literal>_foobar</literal>.
+       The <literal>installShellCompletion</literal> function takes one or more paths to shell completion files. By default it will autodetect the shell type from the completion file extension, but you may also specify it by passing one of <literal>--bash</literal>, <literal>--fish</literal>, or <literal>--zsh</literal>. These flags apply to all paths listed after them (up until another shell flag is given). Each path may also have a custom installation name provided by providing a flag <literal>--name NAME</literal> before the path. If this flag is not provided, zsh completions will be renamed automatically such that <literal>foobar.zsh</literal> becomes <literal>_foobar</literal>. A root name may be provided for all paths using the flag <literal>--cmd NAME</literal>; this synthesizes the appropriate name depending on the shell (e.g. <literal>--cmd foo</literal> will synthesize the name <literal>foo.bash</literal> for bash and <literal>_foo</literal> for zsh). The path may also be a fifo or named fd (such as produced by <literal>&lt;(cmd)</literal>), in which case the shell and name must be provided.
 <programlisting>
 nativeBuildInputs = [ installShellFiles ];
 postInstall = ''
@@ -2069,6 +2081,11 @@ postInstall = ''
   installShellCompletion --zsh --name _foobar share/completions.zsh
   # implicit behavior
   installShellCompletion share/completions/foobar.{bash,fish,zsh}
+  # using named fd
+  installShellCompletion --cmd foobar \
+    --bash &lt;($out/bin/foobar --bash-completion) \
+    --fish &lt;($out/bin/foobar --fish-completion) \
+    --zsh &lt;($out/bin/foobar --zsh-completion)
 '';
 </programlisting>
       </para>