pr-version-check.yml

name: PR version check

on:
  pull_request:
    branches: [main, 'release/*.x']
    types: [opened, edited, labeled, unlabeled, synchronize, reopened]

permissions:
  contents: read
  pull-requests: read

jobs:
  check:
    runs-on: ubuntu-latest
    steps:
    - name: Checkout PR head
      uses: actions/checkout@v6
      with:
        ref: ${{ github.event.pull_request.head.sha }}
        fetch-depth: 0

    - name: Validate version.json against PR labels and history
      shell: pwsh
      env:
        BASE_REF: ${{ github.base_ref }}
        LABELS_JSON: ${{ toJSON(github.event.pull_request.labels.*.name) }}
        PR_AUTHOR: ${{ github.event.pull_request.user.login }}
        HEAD_REF: ${{ github.event.pull_request.head.ref }}
      run: |
        $ErrorActionPreference = 'Stop'

        # The version-bump bot PRs (opened by GITHUB_TOKEN from the automation workflows)
        # legitimately change version.json. Don't trip the manual-edit guard on them;
        # their content is reviewed in the workflow that opened them.
        $isBotBumpPr = ($env:PR_AUTHOR -eq 'github-actions[bot]') -and ($env:HEAD_REF -like 'bot/bump-*' -or $env:HEAD_REF -like 'bot/promote-*')

        $labels = $env:LABELS_JSON | ConvertFrom-Json
        $isBreaking = $labels -contains 'breaking-change'
        $isManualEdit = $labels -contains 'manual-version-edit'

        # Reject any human-authored PR that touches version.json unless explicitly
        # labeled 'manual-version-edit'. version.json is owned by the automation
        # workflows (cut-major, promote-minor, bump-major-preview); manual edits
        # bypass the regression guards and should be a deliberate, labeled exception.
        if (-not $isBotBumpPr) {
          $base = "origin/$env:BASE_REF"
          git fetch origin $env:BASE_REF --quiet
          if ($LASTEXITCODE -ne 0) { throw "git fetch origin $env:BASE_REF failed (exit $LASTEXITCODE)." }
          $diff = git diff --name-only "$base...HEAD"
          if ($LASTEXITCODE -ne 0) { throw "git diff against $base failed (exit $LASTEXITCODE)." }
          if (($diff -split "`r?`n") -contains 'version.json' -and -not $isManualEdit) {
            throw "This PR modifies version.json but is not authored by the automation bot and is not labeled 'manual-version-edit'. version.json is managed by the workflows in .github/workflows/ (cut-major, promote-minor, bump-major-preview). To override (e.g. for the one-time cutover or a recovery operation), add the 'manual-version-edit' label."
          }
        }

        if ($env:BASE_REF -ne 'main') {
          Write-Host "PR targets '$env:BASE_REF' (not main); breaking-change check only applies to PRs targeting main. Skipping."
          exit 0
        }

        if ($isBotBumpPr) {
          Write-Host "PR is an automation-authored version-bump branch ('$env:HEAD_REF'); skipping breaking-change check."
          exit 0
        }

        $headVersionJson = Get-Content version.json -Raw | ConvertFrom-Json
        $headVer = $headVersionJson.version
        if ($headVer -notmatch '^(0|[1-9]\d*)\.') {
          throw "Could not parse major version from PR head version.json: '$headVer'"
        }
        $headMajor = [int]$matches[1]

        git fetch origin main --quiet
        if ($LASTEXITCODE -ne 0) { throw "git fetch origin main failed (exit $LASTEXITCODE)." }

        $baseVersionJson = git show "origin/main:version.json" | ConvertFrom-Json
        if ($LASTEXITCODE -ne 0) { throw "Failed to read version.json from origin/main." }
        $baseVer = $baseVersionJson.version
        if ($baseVer -notmatch '^(0|[1-9]\d*)\.') {
          throw "Could not parse major version from main's version.json: '$baseVer'"
        }
        $baseMajor = [int]$matches[1]

        # Unconditional check: if this PR changes the major in version.json, it MUST be
        # labeled breaking-change. Catches unlabeled major-version edits.
        if ($headMajor -ne $baseMajor -and -not $isBreaking) {
          throw "This PR changes version.json's major from $baseMajor to $headMajor but is not labeled 'breaking-change'. Major-version changes must be tagged."
        }

        if (-not $isBreaking) {
          Write-Host "PR is not labeled 'breaking-change' and does not change the major; no further checks."
          exit 0
        }

        Write-Host "PR is labeled as breaking. Verifying the PR's version.json reflects a newer major than the latest stable release."

        git fetch --tags --force origin
        if ($LASTEXITCODE -ne 0) { throw "git fetch --tags failed (exit $LASTEXITCODE); cannot safely validate breaking-change label." }

        $latestStable = git tag --list --sort=-v:refname |
            Where-Object { $_ -match '^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)$' } |
            Select-Object -First 1

        if (-not $latestStable) {
          # No prior stable releases. Accept either the post-bump steady state
          # (head == base, both already at the new major) or the rare case where
          # the breaking PR itself does the bump (head == base + 1).
          if ($headMajor -eq $baseMajor -or $headMajor -eq $baseMajor + 1) {
            Write-Host "No stable tags found; PR head major ($headMajor) is consistent with main ($baseMajor). OK."
            exit 0
          }
          throw "No stable tags found; PR head major ($headMajor) must equal or be exactly one greater than main's current major ($baseMajor) for a breaking-change PR with no prior stable history."
        }

        if ($latestStable -notmatch '^(\d+)\.') {
          throw "Could not parse latest stable tag: '$latestStable'"
        }
        $latestMajor = [int]$matches[1]

        Write-Host "Latest stable major: $latestMajor; PR head major: $headMajor"

        $expectedMajor = $latestMajor + 1
        if ($headMajor -ne $expectedMajor) {
          if ($headMajor -le $latestMajor) {
            $msg = "PR is labeled breaking-change but its version.json major ($headMajor) is not greater than the latest stable release major ($latestMajor; tag '$latestStable'). Run the 'Bump main to next major preview' workflow with next_major=$expectedMajor first, then rebase this PR onto the updated main."
          } else {
            $msg = "PR is labeled breaking-change but its version.json major ($headMajor) skips past major $expectedMajor. Main must be at exactly latest_stable_major + 1 ($latestMajor + 1 = $expectedMajor). Reset main to $expectedMajor.0-preview.{height} before merging this PR."
          }
          throw $msg
        }

        Write-Host "OK: PR head major ($headMajor) is exactly one greater than latest stable major ($latestMajor)."