From f6467c357419d70d8f32816fe68b9bde6278f8b0 Mon Sep 17 00:00:00 2001 From: Silvan Mosberger Date: Thu, 31 Aug 2023 22:41:09 +0200 Subject: [PATCH] pkgs/by-name: Introduce This introduces the `pkgs/by-name` directory as proposed by RFC 140. Included are: - The implementation to add packages defined in that directory to the top-level package scope - Contributer documentation on how to add packages to it - A GitHub Actions workflow to check the structure of it on all PRs --- .github/CODEOWNERS | 3 + .github/workflows/check-by-name.yml | 49 +++++++++++ pkgs/by-name/README.md | 101 ++++++++++++++++++++++ pkgs/test/nixpkgs-check-by-name/README.md | 3 +- pkgs/top-level/by-name-overlay.nix | 50 +++++++++++ pkgs/top-level/stage.nix | 8 ++ 6 files changed, 213 insertions(+), 1 deletion(-) create mode 100644 .github/workflows/check-by-name.yml create mode 100644 pkgs/by-name/README.md create mode 100644 pkgs/top-level/by-name-overlay.nix diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS index f5679a1a142..79ba7b7c520 100644 --- a/.github/CODEOWNERS +++ b/.github/CODEOWNERS @@ -49,6 +49,9 @@ # pkgs/by-name /pkgs/test/nixpkgs-check-by-name @infinisil +/pkgs/by-name/README.md @infinisil +/pkgs/top-level/by-name-overlay.nix @infinisil +/.github/workflows/check-by-name.nix @infinisil # Nixpkgs build-support /pkgs/build-support/writers @lassulus @Profpatsch diff --git a/.github/workflows/check-by-name.yml b/.github/workflows/check-by-name.yml new file mode 100644 index 00000000000..9622634fcff --- /dev/null +++ b/.github/workflows/check-by-name.yml @@ -0,0 +1,49 @@ +# Checks pkgs/by-name (see pkgs/by-name/README.md) +# using the nixpkgs-check-by-name tool (see pkgs/test/nixpkgs-check-by-name) +name: Check pkgs/by-name + +# The pre-built tool is fetched from a channel, +# making it work predictable on all PRs +on: pull_request + +# The tool doesn't need any permissions, it only outputs success or not based on the checkout +permissions: {} + +jobs: + check: + # This is x86_64-linux, for which the tool is always prebuilt on the nixos-* channels, + # as specified in nixos/release-combined.nix + runs-on: ubuntu-latest + steps: + - uses: actions/checkout@v3 + - uses: cachix/install-nix-action@v22 + - name: Determining channel to use for dependencies + run: | + echo "Determining which channel to use for PR base branch $GITHUB_BASE_REF" + if [[ "$GITHUB_BASE_REF" =~ ^(release|staging|staging-next)-([0-9][0-9]\.[0-9][0-9])$ ]]; then + # Use the release channel for all PRs to release-XX.YY, staging-XX.YY and staging-next-XX.YY + channel=nixos-${BASH_REMATCH[2]} + echo "PR is for a release branch, using release channel $channel" + else + # Use the nixos-unstable channel for all other PRs + channel=nixos-unstable + echo "PR is for a non-release branch, using unstable channel $channel" + fi + echo "channel=$channel" >> "$GITHUB_ENV" + - name: Fetching latest version of channel + run: | + echo "Fetching latest version of channel $channel" + # This is probably the easiest way to get Nix to output the path to a downloaded channel! + nixpkgs=$(nix-instantiate --find-file nixpkgs -I nixpkgs=channel:"$channel") + # This file only exists in channels + rev=$(<"$nixpkgs"/.git-revision) + echo "Channel $channel is at revision $rev" + echo "nixpkgs=$nixpkgs" >> "$GITHUB_ENV" + echo "rev=$rev" >> "$GITHUB_ENV" + - name: Fetching pre-built nixpkgs-check-by-name from the channel + run: | + echo "Fetching pre-built nixpkgs-check-by-name from channel $channel at revision $rev" + # Passing --max-jobs 0 makes sure that we won't build anything + nix-build "$nixpkgs" -A tests.nixpkgs-check-by-name --max-jobs 0 + - name: Running nixpkgs-check-by-name + run: result/bin/nixpkgs-check-by-name . diff --git a/pkgs/by-name/README.md b/pkgs/by-name/README.md new file mode 100644 index 00000000000..8aecc3822cc --- /dev/null +++ b/pkgs/by-name/README.md @@ -0,0 +1,101 @@ +# Name-based package directories + +The structure of this directory maps almost directly to top-level package attributes. +This is the recommended way to add new top-level packages to Nixpkgs [when possible](#limitations). + +## Example + +The top-level package `pkgs.some-package` may be declared by setting up this file structure: + +``` +pkgs +└── by-name + ├── so + ┊ ├── some-package + ┊ └── package.nix + +``` + +Where `some-package` is the package name and `so` is the lowercased 2-letter prefix of the package name. + +The `package.nix` may look like this: + +```nix +# A function taking an attribute set as an argument +{ + # Get access to top-level attributes for use as dependencies + lib, + stdenv, + libbar, + + # Make this derivation configurable using `.override { enableBar = true }` + enableBar ? false, +}: + +# The return value must be a derivation +stdenv.mkDerivation { + # ... + buildInputs = + lib.optional enableBar libbar; +} +``` + +You can also split up the package definition into more files in the same directory if necessary. + +Once defined, the package can be built from the Nixpkgs root directory using: +``` +nix-build -A some-package +``` + +See the [general package conventions](../README.md#conventions) for more information on package definitions. + +### Changing implicit attribute defaults + +The above expression is called using these arguments by default: +```nix +{ + lib = pkgs.lib; + stdenv = pkgs.stdenv; + libbar = pkgs.libbar; +} +``` + +But the package might need `pkgs.libbar_2` instead. +While the function could be changed to take `libbar_2` directly as an argument, +this would change the `.override` interface, breaking code like `.override { libbar = ...; }`. +So instead it is preferable to use the same generic parameter name `libbar` +and override its value in [`pkgs/top-level/all-packages.nix`](../top-level/all-packages.nix): + +```nix +libfoo = callPackage ../by-name/so/somePackage/package.nix { + libbar = libbar_2; +}; +``` + +## Limitations + +There's some limitations as to which packages can be defined using this structure: + +- Only packages defined using `pkgs.callPackage`. + This excludes packages defined using `pkgs.python3Packages.callPackage ...`. + + Instead use the [category hierarchy](../README.md#category-hierarchy) for such attributes. + +- Only top-level packages. + This excludes packages for other package sets like `pkgs.pythonPackages.*`. + + Refer to the definition and documentation of the respective package set to figure out how such packages can be declared. + +## Validation + +CI performs [certain checks](../test/nixpkgs-check-by-name/README.md#validity-checks) on the `pkgs/by-name` structure. +This is done using the [`nixpkgs-check-by-name` tool](../test/nixpkgs-check-by-name). +The version of this tool used is the one that corresponds to the NixOS channel of the PR base branch. +See [here](../../.github/workflows/check-by-name.yml) for details. + +The tool can be run locally using + +```bash +nix-build -A tests.nixpkgs-check-by-name +result/bin/nixpkgs-check-by-name . +``` diff --git a/pkgs/test/nixpkgs-check-by-name/README.md b/pkgs/test/nixpkgs-check-by-name/README.md index 754d0a2090d..4dd694acd2f 100644 --- a/pkgs/test/nixpkgs-check-by-name/README.md +++ b/pkgs/test/nixpkgs-check-by-name/README.md @@ -1,11 +1,12 @@ # Nixpkgs pkgs/by-name checker This directory implements a program to check the [validity](#validity-checks) of the `pkgs/by-name` Nixpkgs directory once introduced. +It is being used by [this GitHub Actions workflow](../../../.github/workflows/check-by-name.yml). This is part of the implementation of [RFC 140](https://github.com/NixOS/rfcs/pull/140). ## API -This API may be changed over time if the CI making use of it is adjusted to deal with the change appropriately, see [Hydra builds](#hydra-builds). +This API may be changed over time if the CI workflow making use of it is adjusted to deal with the change appropriately. - Command line: `nixpkgs-check-by-name ` - Arguments: diff --git a/pkgs/top-level/by-name-overlay.nix b/pkgs/top-level/by-name-overlay.nix new file mode 100644 index 00000000000..41944c4e3b0 --- /dev/null +++ b/pkgs/top-level/by-name-overlay.nix @@ -0,0 +1,50 @@ +# This file turns the pkgs/by-name directory (see its README.md for more info) into an overlay that adds all the defined packages. +# No validity checks are done here, +# instead this file is optimised for performance, +# and validity checks are done by CI on PRs. + +# Type: Path -> Overlay +baseDirectory: +let + # Because of Nix's import-value cache, importing lib is free + lib = import ../../lib; + + inherit (builtins) + readDir + ; + + inherit (lib.attrsets) + mapAttrs + mapAttrsToList + mergeAttrsList + ; + + # Package files for a single shard + # Type: String -> String -> AttrsOf Path + namesForShard = shard: type: + if type != "directory" then + # Ignore all non-directories. Technically only README.md is allowed as a file in the base directory, so we could alternatively: + # - Assume that README.md is the only file and change the condition to `shard == "README.md"` for a minor performance improvement. + # This would however cause very poor error messages if there's other files. + # - Ensure that README.md is the only file, throwing a better error message if that's not the case. + # However this would make for a poor code architecture, because one type of error would have to be duplicated in the validity checks and here. + # Additionally in either of those alternatives, we would have to duplicate the hardcoding of "README.md" + { } + else + mapAttrs + (name: _: baseDirectory + "/${shard}/${name}/package.nix") + (readDir (baseDirectory + "/${shard}")); + + # The attribute set mapping names to the package files defining them + # This is defined up here in order to allow reuse of the value (it's kind of expensive to compute) + # if the overlay has to be applied multiple times + packageFiles = mergeAttrsList (mapAttrsToList namesForShard (readDir baseDirectory)); +in +# TODO: Consider optimising this using `builtins.deepSeq packageFiles`, +# which could free up the above thunks and reduce GC times. +# Currently this would be hard to measure until we have more packages +# and ideally https://github.com/NixOS/nix/pull/8895 +self: super: +mapAttrs (name: file: + self.callPackage file { } +) packageFiles diff --git a/pkgs/top-level/stage.nix b/pkgs/top-level/stage.nix index 3886ae04e49..1f37bbb70bd 100644 --- a/pkgs/top-level/stage.nix +++ b/pkgs/top-level/stage.nix @@ -8,6 +8,13 @@ arguments. Normal users should not import this directly but instead import `pkgs/default.nix` or `default.nix`. */ +let + # An overlay to auto-call packages in ../by-name. + # By defining it at the top of the file, + # this value gets reused even if this file is imported multiple times, + # thanks to Nix's import-value cache. + autoCalledPackages = import ./by-name-overlay.nix ../by-name; +in { ## Misc parameters kept the same for all stages ## @@ -279,6 +286,7 @@ let stdenvAdapters trivialBuilders splice + autoCalledPackages allPackages otherPackageSets aliases