.github/workflows/mypy_primer_comment.yml

name: Comment with mypy_primer diff

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

permissions:
  contents: read
  pull-requests: write

jobs:
  comment:
    name: Comment PR from mypy_primer
    runs-on: ubuntu-latest
    steps:
      - name: Download diffs
        uses: actions/github-script@v3
        with:
          script: |
            const fs = require('fs');
            const artifacts = await github.actions.listWorkflowRunArtifacts({
               owner: context.repo.owner,
               repo: context.repo.repo,
               run_id: ${{ github.event.workflow_run.id }},
            });
            const [matchArtifact] = artifacts.data.artifacts.filter((artifact) =>
              artifact.name == "mypy_primer_diffs");

            const download = await github.actions.downloadArtifact({
               owner: context.repo.owner,
               repo: context.repo.repo,
               artifact_id: matchArtifact.id,
               archive_format: "zip",
            });
            fs.writeFileSync("diff.zip", Buffer.from(download.data));

      - run: unzip diff.zip

      # Based on https://github.com/kanga333/comment-hider
      - name: Hide old comments
        uses: actions/github-script@v3
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const fs = require('fs')

            const response = await github.issues.listComments({
              issue_number: fs.readFileSync("pr_number.txt", { encoding: "utf8" }),
              owner: context.repo.owner,
              repo: context.repo.repo,
            })
            const botCommentIds = response.data
              .filter(comment => comment.user.login === 'github-actions[bot]')
              .map(comment => comment.node_id)

            for (const id of botCommentIds) {
              const resp = await github.graphql(`
                mutation {
                  minimizeComment(input: {classifier: OUTDATED, subjectId: "${id}"}) {
                    minimizedComment {
                      isMinimized
                    }
                  }
                }
              `)
              if (resp.errors) {
                throw new Error(resp.errors)
              }
            }

      - name: Post comment
        uses: actions/github-script@v3
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const fs = require('fs')
            // Keep in sync with shards produced by mypy_primer workflow
            const data = (
              ['diff_0.txt', 'diff_1.txt', 'diff_2.txt']
              .map(fileName => fs.readFileSync(fileName, { encoding: 'utf8' }))
              .join('')
              .substr(0, 30000)  // About 300 lines
            )

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

            if (data.trim()) {
              const 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 + '```'
              await github.issues.createComment({
                issue_number: fs.readFileSync("pr_number.txt", { encoding: "utf8" }),
                owner: context.repo.owner,
                repo: context.repo.repo,
                body
              })
            }