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Support previews for stacked pull requests #1807

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9af5a3b
Support previews for stacked pull requests
st0012 Sep 1, 2026
de8eaca
Preserve previews for shared-head pull requests
st0012 Sep 5, 2026
90bd79b
Remove preview workflow tests
st0012 Sep 5, 2026
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106 changes: 64 additions & 42 deletions .github/workflows/cloudflare-preview.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -19,25 +19,22 @@ jobs:
actions: read
pull-requests: read
outputs:
current: ${{ steps.resolve.outputs.current }}
number: ${{ steps.resolve.outputs.number }}
head_sha: ${{ steps.resolve.outputs.head_sha }}
pull_requests: ${{ steps.resolve.outputs.pull_requests }}
steps:
# A forked workflow_run can omit pull request details, so the artifact
# must match the exact open pull request and commit.
- name: Resolve current pull request and artifact
# must match the source repository, branch, and commit of each open PR.
- name: Resolve current pull requests and artifact
id: resolve
uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
with:
script: |
const run = context.payload.workflow_run;
const expectedRepository = 'ruby/rdoc';
const expectedBase = 'master';
const artifactName = 'pr-preview-site';
const maximumArchiveBytes = 500 * 1024 * 1024;
core.setOutput('pull_requests', '[]');

if (!['success', 'failure'].includes(run.conclusion)) {
core.setOutput('current', 'false');
core.notice(`Skipped a preview build with conclusion: ${run.conclusion}.`);
return;
}
Expand Down Expand Up @@ -66,7 +63,6 @@ jobs:
repo: context.repo.repo,
state: 'open',
head: `${headOwner}:${headBranch}`,
base: expectedBase,
per_page: 100,
});
candidateNumbers = new Set(
Expand All @@ -77,7 +73,6 @@ jobs:
}

if (candidateNumbers.size === 0) {
core.setOutput('current', 'false');
core.notice('No open pull request uses this preview build.');
return;
}
Expand All @@ -93,25 +88,15 @@ jobs:
}

const matches = candidates.filter(pull =>
pull.state === 'open' &&
pull.base.repo.full_name === expectedRepository &&
pull.base.ref === expectedBase &&
pull.head.repo?.full_name === headRepository &&
pull.head.ref === headBranch
pull.head.ref === headBranch &&
pull.head.sha === run.head_sha
);

if (matches.length !== 1) {
core.setFailed(`Expected one pull request for this preview build, found ${matches.length}.`);
return;
}

const pull = matches[0];
const current = pull.state === 'open' && pull.head.sha === run.head_sha;
core.setOutput('current', current.toString());
core.setOutput('number', pull.number.toString());
core.setOutput('head_sha', run.head_sha);

if (!current) {
core.notice('The pull request changed or closed after this preview build.');
if (matches.length === 0) {
core.notice('No current open pull request uses this preview build.');
return;
}

Expand All @@ -130,11 +115,26 @@ jobs:
);

if (matchingArtifacts.length === 0 && run.conclusion === 'failure') {
core.setOutput('current', 'false');
core.notice('The failed preview build did not publish an artifact.');
return;
}

// Title and body edits skip the build job but can still complete successfully.
// Keep missing uploads an error when a build actually ran.
if (matchingArtifacts.length === 0) {
const jobs = await github.paginate(github.rest.actions.listJobsForWorkflowRun, {
owner: context.repo.owner,
repo: context.repo.repo,
run_id: run.id,
filter: 'latest',
per_page: 100,
});
if (jobs.length > 0 && jobs.every(job => job.conclusion === 'skipped')) {
core.notice('The preview build was skipped.');
return;
}
}

if (matchingArtifacts.length !== 1) {
core.setFailed(`Expected one ${artifactName} artifact, found ${matchingArtifacts.length}.`);
return;
Expand All @@ -143,16 +143,30 @@ jobs:
const artifact = matchingArtifacts[0];
if (artifact.size_in_bytes <= 0 || artifact.size_in_bytes > maximumArchiveBytes) {
core.setFailed(`The preview artifact archive has an invalid size: ${artifact.size_in_bytes} bytes.`);
return;
}

// The site comes from the head commit, not a merge with the base branch.
// PRs with the same source repository, branch, and commit can share it.
core.setOutput('pull_requests', JSON.stringify(matches.map(pull => ({
number: pull.number,
head_sha: run.head_sha,
base_ref: pull.base.ref,
}))));

deploy:
name: Deploy Preview
name: Deploy Preview for PR ${{ matrix.pull_request.number }}
needs: resolve
if: needs.resolve.outputs.current == 'true'
if: needs.resolve.outputs.pull_requests != '[]'
runs-on: ubuntu-latest
timeout-minutes: 15
# Each PR keeps its own preview and stale-data checks, even when the source is shared.
strategy:
fail-fast: false
matrix:
pull_request: ${{ fromJSON(needs.resolve.outputs.pull_requests) }}
concurrency:
group: pr-preview-deploy-${{ needs.resolve.outputs.number }}
group: pr-preview-deploy-${{ matrix.pull_request.number }}
cancel-in-progress: true
permissions:
actions: read
Expand Down Expand Up @@ -254,18 +268,22 @@ jobs:
core.info(`Accepted ${fileCount} static files (${totalBytes} bytes).`);

# The pull request can change after artifact selection. A second head
# comparison blocks deployment of a stale commit.
- name: Confirm pull request head
# and base comparison blocks deployment with stale pull request data.
- name: Confirm pull request head and base
id: current
uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
env:
PR_NUMBER: ${{ needs.resolve.outputs.number }}
EXPECTED_SHA: ${{ needs.resolve.outputs.head_sha }}
PR_NUMBER: ${{ matrix.pull_request.number }}
EXPECTED_SHA: ${{ matrix.pull_request.head_sha }}
EXPECTED_BASE_REF: ${{ matrix.pull_request.base_ref }}
with:
script: |
const number = process.env.PR_NUMBER;
const expectedSha = process.env.EXPECTED_SHA;
if (!/^[1-9][0-9]*$/.test(number) || !/^[0-9a-f]{40}$/.test(expectedSha)) {
const expectedBaseRef = process.env.EXPECTED_BASE_REF;
if (!/^[1-9][0-9]*$/.test(number) ||
!/^[0-9a-f]{40}$/.test(expectedSha) ||
!expectedBaseRef) {
core.setFailed('The resolved pull request metadata is invalid.');
return;
}
Expand All @@ -278,7 +296,7 @@ jobs:
const current =
pull.state === 'open' &&
pull.base.repo.full_name === 'ruby/rdoc' &&
pull.base.ref === 'master' &&
pull.base.ref === expectedBaseRef &&
pull.head.sha === expectedSha;

core.setOutput('current', current.toString());
Expand All @@ -305,29 +323,33 @@ jobs:
command: >-
pages deploy "${{ runner.temp }}/pr-preview-site"
--project-name=rdoc
--branch="${{ needs.resolve.outputs.number }}-preview"
--commit-hash="${{ needs.resolve.outputs.head_sha }}"
--branch="${{ matrix.pull_request.number }}-preview"
--commit-hash="${{ matrix.pull_request.head_sha }}"

# The workflow reuses one marked comment to avoid notification spam and
# show the exact commit for the preview.
# The workflow rechecks the pull request after deployment, then reuses
# one marked comment to avoid stale links and notification spam.
- name: Update preview comment
if: steps.current.outputs.current == 'true'
uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
env:
PR_NUMBER: ${{ needs.resolve.outputs.number }}
EXPECTED_SHA: ${{ needs.resolve.outputs.head_sha }}
PR_NUMBER: ${{ matrix.pull_request.number }}
EXPECTED_SHA: ${{ matrix.pull_request.head_sha }}
EXPECTED_BASE_REF: ${{ matrix.pull_request.base_ref }}
PREVIEW_ALIAS_URL: ${{ steps.deploy.outputs.pages-deployment-alias-url }}
PREVIEW_DEPLOYMENT_URL: ${{ steps.deploy.outputs.deployment-url }}
with:
script: |
const marker = '<!-- rdoc-pr-preview -->';
const number = process.env.PR_NUMBER;
const expectedSha = process.env.EXPECTED_SHA;
const expectedBaseRef = process.env.EXPECTED_BASE_REF;
const previewUrl = (
process.env.PREVIEW_ALIAS_URL || process.env.PREVIEW_DEPLOYMENT_URL || ''
).trim();

if (!/^[1-9][0-9]*$/.test(number) || !/^[0-9a-f]{40}$/.test(expectedSha)) {
if (!/^[1-9][0-9]*$/.test(number) ||
!/^[0-9a-f]{40}$/.test(expectedSha) ||
!expectedBaseRef) {
core.setFailed('The preview comment metadata is invalid.');
return;
}
Expand All @@ -353,7 +375,7 @@ jobs:
const current =
pull.state === 'open' &&
pull.base.repo.full_name === 'ruby/rdoc' &&
pull.base.ref === 'master' &&
pull.base.ref === expectedBaseRef &&
pull.head.sha === expectedSha;
if (!current) {
core.notice('Skipped the preview comment because the pull request changed.');
Expand Down
15 changes: 9 additions & 6 deletions .github/workflows/pr-preview-check.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -2,21 +2,24 @@ name: Build PR Preview

on:
pull_request:
types: [opened, synchronize, reopened]
types: [opened, synchronize, reopened, edited]

permissions:
contents: read

concurrency:
group: pr-preview-build-${{ github.event.pull_request.number }}
cancel-in-progress: true

jobs:
build:
name: Build Preview
if: github.repository == 'ruby/rdoc'
# Base retargets need a preview, but title and body edits do not change the site.
if: >-
github.repository == 'ruby/rdoc' &&
(github.event.action != 'edited' || github.event.changes.base)
runs-on: ubuntu-latest
timeout-minutes: 20
# A skipped edit must not cancel an active build for the same PR.
concurrency:
group: pr-preview-build-${{ github.event.pull_request.number }}
cancel-in-progress: true
steps:
# This job executes untrusted pull request code. It must not receive secrets
# or a token with write access.
Expand Down