buildDotnetModule: add passthru.fetch-deps

1 files changed, 5 insertions, 2 deletions

diff --git a/doc/languages-frameworks/dotnet.section.md b/doc/languages-frameworks/dotnet.section.md
index 94d97a970dbb1..159347008e80c 100644
--- a/doc/languages-frameworks/dotnet.section.md
+++ b/doc/languages-frameworks/dotnet.section.md
@@ -72,7 +72,7 @@ The `dotnetCorePackages.sdk` contains both a runtime and the full sdk of a given
 To package Dotnet applications, you can use `buildDotnetModule`. This has similar arguments to `stdenv.mkDerivation`, with the following additions:
 
 * `projectFile` has to be used for specifying the dotnet project file relative to the source root. These usually have `.sln` or `.csproj` file extensions. This can be an array of multiple projects as well.
-* `nugetDeps` has to be used to specify the NuGet dependency file. Unfortunately, these cannot be deterministically fetched without a lockfile. This file should be generated using `nuget-to-nix` tool, which is available in nixpkgs.
+* `nugetDeps` has to be used to specify the NuGet dependency file. Unfortunately, these cannot be deterministically fetched without a lockfile. A script to fetch these is available as `passthru.fetch-deps`. This file can also be generated manually using `nuget-to-nix` tool, which is available in nixpkgs.
 * `packNupkg` is used to pack project as a `nupkg`, and installs it to `$out/share`. If set to `true`, the derivation can be used as a dependency for another dotnet project by adding it to `projectReferences`.
 * `projectReferences` can be used to resolve `ProjectReference` project items. Referenced projects can be packed with `buildDotnetModule` by setting the `packNupkg = true` attribute and passing a list of derivations to `projectReferences`. Since we are sharing referenced projects as NuGets they must be added to csproj/fsproj files as `PackageReference` as well.
  For example, your project has a local dependency:
@@ -99,6 +99,8 @@ To package Dotnet applications, you can use `buildDotnetModule`. This has simila
 * `dotnetPackFlags` can be used to pass flags to `dotnet pack`. Used only if `packNupkg` is set to `true`.
 * `dotnetFlags` can be used to pass flags to all of the above phases.
 
+When packaging a new application, you need to fetch it's dependencies. You can set `nugetDeps` to an empty string to make the derivation temporarily evaluate, and then run `nix-build -A package.passthru.fetch-deps` to generate it's dependency fetching script. After running the script, you should have the location of the generated lockfile printed to the console. This can be copied to a stable directory. Note that if either `projectFile` or `nugetDeps` are unset, this script cannot be generated!
+
 Here is an example `default.nix`, using some of the previously discussed arguments:
 ```nix
 { lib, buildDotnetModule, dotnetCorePackages, ffmpeg }:
@@ -112,7 +114,8 @@ in buildDotnetModule rec {
   src = ./.;
 
   projectFile = "src/project.sln";
-  nugetDeps = ./deps.nix; # File generated with `nuget-to-nix path/to/src > deps.nix`.
+  nugetDeps = ./deps.nix; # File generated with `nix-build -A package.passthru.fetch-deps`.
+
   projectReferences = [ referencedProject ]; # `referencedProject` must contain `nupkg` in the folder structure.
 
   dotnet-sdk = dotnetCorePackages.sdk_3_1;