Merge pull request #274591 from tweag/by-name-reproducible

# Checks pkgs/by-name (see pkgs/by-name/README.md)

# using the nixpkgs-check-by-name tool (see pkgs/test/nixpkgs-check-by-name)

#

# When you make changes to this workflow, also update pkgs/test/nixpkgs-check-by-name/scripts/run-local.sh adequately

name: Check pkgs/by-name

# The pre-built tool is fetched from a channel,

    # The default of 6 hours is definitely too long

    timeout-minutes: 10

    steps:

      # This step has to be in this file,

      # because it's needed to determine which revision of the repository to fetch,

      # and we can only use other files from the repository once it's fetched.

      - name: Resolving the merge commit

        env:

          GH_TOKEN: ${{ github.token }}

          ref: ${{ env.mergedSha }}

          # Fetches the merge commit and its parents

          fetch-depth: 2

      - name: Determining PR git hashes

      - name: Checking out base branch

        run: |

          # For pull_request_target this is the same as $GITHUB_SHA

          echo "baseSha=$(git rev-parse HEAD^1)" >> "$GITHUB_ENV"

          echo "headSha=$(git rev-parse HEAD^2)" >> "$GITHUB_ENV"

          base=$(mktemp -d)

          git worktree add "$base" "$(git rev-parse HEAD^1)"

          echo "base=$base" >> "$GITHUB_ENV"

      - uses: cachix/install-nix-action@7ac1ec25491415c381d9b62f0657c7a028df52a7 # v24

      - name: Determining channel to use for dependencies

        run: |

          echo "Determining the preferred 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, preferred channel is $channel"

          else

              # Use the nixos-unstable channel for all other PRs

              channel=nixos-unstable

              echo "PR is for a non-release branch, preferred channel is $channel"

          fi

          # Check that the channel exists. It doesn't exist for fresh release branches

          if ! curl -fSs "https://channels.nixos.org/$channel"; then

            # Fall back to nixos-unstable, makes sense for fresh release branches

            echo "Preferred channel $channel could not be fetched, falling back to nixos-unstable"

            channel=nixos-unstable

          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: Fetching the tool

        run: pkgs/test/nixpkgs-check-by-name/scripts/fetch-tool.sh "$GITHUB_BASE_REF" result

      - name: Running nixpkgs-check-by-name

        run: |

          echo "Checking whether the check succeeds on the base branch $GITHUB_BASE_REF"

          git checkout -q "$baseSha"

          if baseOutput=$(result/bin/nixpkgs-check-by-name . 2>&1); then

            baseSuccess=1

          else

            baseSuccess=

          fi

          printf "%s\n" "$baseOutput"

          echo "Checking whether the check would succeed after merging this pull request"

          git checkout -q "$mergedSha"

          if mergedOutput=$(result/bin/nixpkgs-check-by-name . 2>&1); then

            mergedSuccess=1

            exitCode=0

          else

            mergedSuccess=

            exitCode=1

          fi

          printf "%s\n" "$mergedOutput"

          resultToEmoji() {

            if [[ -n "$1" ]]; then

              echo ":heavy_check_mark:"

          if result/bin/nixpkgs-check-by-name --base "$base" .; then

            exit 0

          else

              echo ":x:"

            fi

          }

          # Print a markdown summary in GitHub actions

          {

            echo "| Nixpkgs version | Check result |"

            echo "| --- | --- |"

            echo "| Latest base commit | $(resultToEmoji "$baseSuccess") |"

            echo "| After merging this PR | $(resultToEmoji "$mergedSuccess") |"

            echo ""

            if [[ -n "$baseSuccess" ]]; then

              if [[ -n "$mergedSuccess" ]]; then

                echo "The check succeeds on both the base branch and after merging this PR"

              else

                echo "The check succeeds on the base branch, but would fail after merging this PR:"

                echo "\`\`\`"

                echo "$mergedOutput"

                echo "\`\`\`"

                echo ""

              fi

            else

              if [[ -n "$mergedSuccess" ]]; then

                echo "The check fails on the base branch, but this PR fixes it, nicely done!"

              else

                echo "The check fails on both the base branch and after merging this PR, unknown if only this PRs changes would satisfy the check, the base branch needs to be fixed first."

                echo ""

                echo "Failure on the base branch:"

                echo "\`\`\`"

                echo "$baseOutput"

                echo "\`\`\`"

                echo ""

                echo "Failure after merging this PR:"

                echo "\`\`\`"

                echo "$mergedOutput"

                echo "\`\`\`"

                echo ""

              fi

            fi

            echo "### Details"

            echo "- nixpkgs-check-by-name tool:"

            echo "  - Channel: $channel"

            echo "  - Nixpkgs commit: [$rev](https://github.com/${GITHUB_REPOSITORY}/commit/$rev)"

            echo "  - Store path: \`$(realpath result)\`"

            echo "- Tested Nixpkgs:"

            echo "  - Base branch: $GITHUB_BASE_REF"

            echo "  - Latest base branch commit: [$baseSha](https://github.com/${GITHUB_REPOSITORY}/commit/$baseSha)"

            echo "  - Latest PR commit: [$headSha](https://github.com/${GITHUB_REPOSITORY}/commit/$headSha)"

            echo "  - Merge commit: [$mergedSha](https://github.com/${GITHUB_REPOSITORY}/commit/$mergedSha)"

          } >> "$GITHUB_STEP_SUMMARY"

            exitCode=$?

            echo "To run locally: ./maintainers/scripts/check-by-name.sh $GITHUB_BASE_REF https://github.com/$GITHUB_REPOSITORY.git"

            exit "$exitCode"

          fi

## Metadata

### `check-by-name.sh`

An alias for `pkgs/test/nixpkgs-check-by-name/scripts/run-local.sh`, see [documentation](../../pkgs/test/nixpkgs-check-by-name/scripts/README.md).

### `get-maintainer.sh`

`get-maintainer.sh [selector] value` returns a JSON object describing

../../pkgs/test/nixpkgs-check-by-name/scripts/run-local.sh

 No newline at end of file

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

You can locally emulate the CI check using

```bash

nix-build -A tests.nixpkgs-check-by-name

result/bin/nixpkgs-check-by-name .

```

$ ./pkgs/test/nixpkgs-check-by-name/scripts/run-local.sh master

```

See [here](../../.github/workflows/check-by-name.yml) for more info.

# CI-related Scripts

This directory contains scripts used and related to the CI running the `pkgs/by-name` checks in Nixpkgs. See also the [CI GitHub Action](../../../../.github/workflows/check-by-name.yml).

## `./run-local.sh BASE_BRANCH [REPOSITORY]`

Runs the `pkgs/by-name` check on the HEAD commit, closely matching what CI does.

Note that this can't do exactly the same as CI,

because CI needs to rely on GitHub's server-side Git history to compute the mergeability of PRs before the check can be started.

In turn when running locally, we don't want to have to push commits to test them,

and we can also rely on the local Git history to do the mergeability check.

Arguments:

- `BASE_BRANCH`: The base branch to use, e.g. master or release-23.11

- `REPOSITORY`: The repository to fetch the base branch from, defaults to https://github.com/NixOS/nixpkgs.git

## `./fetch-tool.sh BASE_BRANCH OUTPUT_PATH`

Fetches the Hydra-prebuilt nixpkgs-check-by-name to use from the NixOS channel corresponding to the given base branch.

This script is used both by [`./run-local.sh`](#run-local-sh-base-branch-repository) and CI.

Arguments:

- `BASE_BRANCH`: The base branch to use, e.g. master or release-23.11

- `OUTPUT_PATH`: The output symlink path for the tool