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author | Rebecca Turner <rbt@sent.as> | 2023-04-28 10:04:05 -0700 |
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committer | Rebecca Turner <rbt@sent.as> | 2023-05-25 14:36:18 -0700 |
commit | ec2938bfa5f98b43e5f87ba510ba3cdebaa16496 (patch) | |
tree | adf041b0ad244225b3c37f87e5f1ff1456bb7b8a /doc/languages-frameworks | |
parent | 1535bd0c58e0f7a093bea8d15e37f0cc1a719db2 (diff) |
Document incremental build support for Haskell
Diffstat (limited to 'doc/languages-frameworks')
-rw-r--r-- | doc/languages-frameworks/haskell.section.md | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/doc/languages-frameworks/haskell.section.md b/doc/languages-frameworks/haskell.section.md index a36843c97c61e..894eba1494e5a 100644 --- a/doc/languages-frameworks/haskell.section.md +++ b/doc/languages-frameworks/haskell.section.md @@ -276,6 +276,15 @@ Defaults to `true`. : Whether to generate an index for interactive navigation of the HTML documentation. Defaults to `true` if supported. +`doInstallIntermediates` +: Whether to install intermediate build products (files written to `dist/build` +by GHC during the build process). With `enableSeparateIntermediatesOutput`, +these files are instead installed to [a separate `intermediates` +output.][multiple-outputs] The output can then be passed into a future build of +the same package with the `previousIntermediates` argument to support +incremental builds. See [“Incremental builds”](#haskell-incremental-builds) for +more information. Defaults to `false`. + `enableLibraryProfiling` : Whether to enable [profiling][profiling] for libraries contained in the package. Enabled by default if supported. @@ -371,6 +380,12 @@ Defaults to `false`. : Whether to install documentation to a separate `doc` output. Is automatically enabled if `doHaddock` is `true`. +`enableSeparateIntermediatesOutput` +: When `doInstallIntermediates` is true, whether to install intermediate build +products to a separate `intermediates` output. See [“Incremental +builds”](#haskell-incremental-builds) for more information. Defaults to +`false`. + `allowInconsistentDependencies` : If enabled, allow multiple versions of the same Haskell package in the dependency tree at configure time. Often in such a situation compilation would @@ -381,6 +396,11 @@ later fail because of type mismatches. Defaults to `false`. when loading the library in the REPL, but requires extra build time and disk space. Defaults to `false`. +`previousIntermediates` +: If non-null, intermediate build artifacts are copied from this input to +`dist/build` before performing compiling. See [“Incremental +builds”](#haskell-incremental-builds) for more information. Defaults to `null`. + `buildTarget` : Name of the executable or library to build and install. If unset, all available targets are built and installed. @@ -496,6 +516,54 @@ the [Meta-attributes section](#chap-meta) for their documentation. * `broken` * `hydraPlatforms` +### Incremental builds {#haskell-incremental-builds} + +`haskellPackages.mkDerivation` supports incremental builds for GHC 9.4 and +newer with the `doInstallIntermediates`, `enableSeparateIntermediatesOutput`, +and `previousIntermediates` arguments. + +The basic idea is to first perform a full build of the package in question, +save its intermediate build products for later, and then copy those build +products into the build directory of an incremental build performed later. +Then, GHC will use those build artifacts to avoid recompiling unchanged +modules. + +For more detail on how to store and use incremental build products, see +[Gabriella Gonzalez’ blog post “Nixpkgs support for incremental Haskell +builds”.][incremental-builds] motivation behind this feature. + +An incremental build for [the `turtle` package][turtle] can be performed like +so: + +```nix +let + pkgs = import <nixpkgs> {}; + inherit (pkgs) haskell; + inherit (haskell.lib.compose) overrideCabal; + + # Incremental builds work with GHC >=9.4. + turtle = haskell.packages.ghc944.turtle; + + # This will do a full build of `turtle`, while writing the intermediate build products + # (compiled modules, etc.) to the `intermediates` output. + turtle-full-build-with-incremental-output = overrideCabal (drv: { + doInstallIntermediates = true; + enableSeparateIntermediatesOutput = true; + }) turtle; + + # This will do an incremental build of `turtle` by copying the previously + # compiled modules and intermediate build products into the source tree + # before running the build. + # + # GHC will then naturally pick up and reuse these products, making this build + # complete much more quickly than the previous one. + turtle-incremental-build = overrideCabal (drv: { + previousIntermediates = turtle-full-build-with-incremental-output.intermediates; + }) turtle; +in + turtle-incremental-build +``` + ## Development environments {#haskell-development-environments} In addition to building and installing Haskell software, nixpkgs can also @@ -1083,8 +1151,11 @@ on the issue linked above. [haskell.nix]: https://input-output-hk.github.io/haskell.nix/index.html [HLS user guide]: https://haskell-language-server.readthedocs.io/en/latest/configuration.html#configuring-your-editor [hoogle]: https://wiki.haskell.org/Hoogle +[incremental-builds]: https://www.haskellforall.com/2022/12/nixpkgs-support-for-incremental-haskell.html [jailbreak-cabal]: https://github.com/NixOS/jailbreak-cabal/ +[multiple-outputs]: https://nixos.org/manual/nixpkgs/stable/#chap-multiple-output [optparse-applicative-completions]: https://github.com/pcapriotti/optparse-applicative/blob/7726b63796aa5d0df82e926d467f039b78ca09e2/README.md#bash-zsh-and-fish-completions [profiling-detail]: https://cabal.readthedocs.io/en/latest/cabal-project.html#cfg-field-profiling-detail [profiling]: https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.html [search.nixos.org]: https://search.nixos.org +[turtle]: https://hackage.haskell.org/package/turtle |