mypy_primer_comment.yaml

# This workflow runs when the "Run mypy_primer on PR" workflow completes.
# It downloads the diff from the other workflow instances and creates
# a summary comment in the PR.
name: Comment with mypy_primer diff

on:
  workflow_run:
    workflows:
      - Run mypy_primer on PR
    types:
      - completed

permissions:
  contents: read
  pull-requests: write

jobs:
  comment:
    name: Comment PR from mypy_primer
    runs-on: ubuntu-latest
    if: ${{ github.event.workflow_run.conclusion == 'success' }}
    steps:
      - name: Download diffs
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
               owner: context.repo.owner,
               repo: context.repo.repo,
               run_id: ${{ github.event.workflow_run.id }},
            });
            const matchedArtifacts = artifacts.data.artifacts.filter((artifact) =>
              artifact.name.startsWith("mypy_primer_diffs"));

            for (let i = 0; i < matchedArtifacts.length; i++) {
              const matchArtifact = matchedArtifacts[i];
              const download = await github.rest.actions.downloadArtifact({
                owner: context.repo.owner,
                repo: context.repo.repo,
                artifact_id: matchArtifact.id,
                archive_format: "zip",
              });
              fs.writeFileSync(`diff_${i}.zip`, Buffer.from(download.data));
            }

      - run: unzip diff_\*.zip
      - run: |
          cat diff_*.txt | tee fulldiff.txt

      - name: Post comment
        id: post-comment
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const MAX_CHARACTERS = 30000
            const MAX_CHARACTERS_PER_PROJECT = MAX_CHARACTERS / 3

            const fs = require('fs')
            let data = fs.readFileSync('fulldiff.txt', { encoding: 'utf8' })

            function truncateIfNeeded(original, maxLength) {
              if (original.length <= maxLength) {
                return original
              }
              let truncated = original.substring(0, maxLength)
              // further, remove last line that might be truncated
              truncated = truncated.substring(0, truncated.lastIndexOf('\n'))
              let lines_truncated = original.split('\n').length - truncated.split('\n').length
              return `${truncated}\n\n... (truncated ${lines_truncated} lines) ...`
            }

            const projects = data.split('\n\n')
            // don't let one project dominate
            data = projects.map(project => truncateIfNeeded(project, MAX_CHARACTERS_PER_PROJECT)).join('\n\n')
            // posting comment fails if too long, so truncate
            data = truncateIfNeeded(data, MAX_CHARACTERS)

            console.log("Diff from mypy_primer:")
            console.log(data)

            let body
            if (data.trim()) {
              body = 'Diff from [mypy_primer](https://github.com/hauntsaninja/mypy_primer), showing the effect of this PR on open source code:\n```diff\n' + data + '```'
            } else {
              body = "According to [mypy_primer](https://github.com/hauntsaninja/mypy_primer), this change doesn't affect type check results on a corpus of open source code. ✅"
            }
            const prNumber = parseInt(fs.readFileSync("pr_number.txt", { encoding: "utf8" }))
            await github.rest.issues.createComment({
              issue_number: prNumber,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body
            })
            return prNumber

      - name: Hide old comments
        # v0.4.0
        uses: kanga333/comment-hider@c12bb20b48aeb8fc098e35967de8d4f8018fffdf
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}
          leave_visible: 1
          issue_number: ${{ steps.post-comment.outputs.result }}