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fix: clear stale pr-queue-hygiene conflict marker and paginate comments #433

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Merged
mrbobbytables merged 1 commit into from
Sep 22, 2026
Merged

fix: clear stale pr-queue-hygiene conflict marker and paginate comments #433

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114 changes: 100 additions & 14 deletions scripts/pr-queue-hygiene.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,14 @@
// Otherwise any commenter could post a far-future marker to exempt a PR
// from the 48h gate forever, or a backdated one to have this job label
// and nag somebody else's freshly-conflicting PR.
// 5. Marker clearing: when a PR stops conflicting, its first-conflict
// marker is neutralized with a trusted "resolved" marker (and the
// `needs-rebase-or-close` label is removed), so a later reconflict
// starts a fresh 48h window instead of inheriting the old marker's
// timestamp and being flagged as stale immediately.
// 6. Comment pagination: issue comments are fetched a page at a time
// instead of relying on a single `per_page=100` call, so a marker
// posted early in a PR with a long comment thread is still found.
//
// Usage: node scripts/pr-queue-hygiene.mjs
// Requires `gh` authenticated with `pull-requests: write` on this repo (as
Expand All @@ -46,6 +54,13 @@ export const HOLD_LABELS = new Set(['hold', 'on-hold', 'do-not-merge']);
export const MARKER_PREFIX = '<!-- pr-queue-hygiene:first-conflict-observed:';
const MARKER_RE = /<!-- pr-queue-hygiene:first-conflict-observed:(.+?) -->/;

// Posted once a previously-conflicting PR is observed as no longer
// conflicting, so a later re-conflict starts a fresh 48h window instead of
// inheriting the stale first-conflict marker's timestamp (see
// findFirstConflictObservedAt).
export const RESOLVED_MARKER_PREFIX = '<!-- pr-queue-hygiene:resolved:';
const RESOLVED_MARKER_RE = /<!-- pr-queue-hygiene:resolved:(.+?) -->/;

// Logins whose markers are believed. The marker is this job's state store,
// but it is kept in a comment thread every GitHub user can write to, so an
// unauthenticated marker is an unauthenticated state write.
Expand All @@ -68,26 +83,53 @@ export function isTrustedMarkerComment(
return trustedLogins.has(String(user.login || '').toLowerCase());
}

// A resolved marker is trusted under the same rule as a first-conflict
// marker: only a bot login on the allowlist can clear the state, otherwise
// anyone could post a fake resolution to reset another PR's 48h clock.
export function isTrustedResolvedComment(
comment,
trustedLogins = TRUSTED_MARKER_AUTHORS,
) {
return isTrustedMarkerComment(comment, trustedLogins);
}

// Extracts the first-conflict-observed timestamp (if any) from a PR's
// issue comments, by finding this script's own hidden marker comment.
//
// Markers from anyone else are ignored rather than returned, and so are
// markers whose payload is not a parseable past timestamp: a future value
// would make hoursSince() negative and exempt the PR from the stale gate
// permanently. Scanning continues past a rejected marker so a spoofed
// comment cannot hide the genuine one behind it. When nothing is trusted the
// caller records a fresh marker, so the state self-heals.
// Comments are scanned in ascending (oldest-first) order. A trusted
// "resolved" marker clears any first-conflict marker seen so far, so a PR
// that stopped conflicting and later reconflicts gets a fresh candidate
// timestamp from the marker posted *after* the resolution, rather than
// reporting the stale pre-resolution marker and being immediately flagged
// as >48h stale. Markers from anyone else are ignored rather than
// returned, and so are markers whose payload is not a parseable past
// timestamp: a future value would make hoursSince() negative and exempt
// the PR from the stale gate permanently. Scanning continues past a
// rejected marker so a spoofed comment cannot hide the genuine one behind
// it. When nothing is trusted the caller records a fresh marker, so the
// state self-heals.
export function findFirstConflictObservedAt(comments, options = {}) {
const { isTrusted = isTrustedMarkerComment, now = Date.now() } = options;
const {
isTrusted = isTrustedMarkerComment,
isResolvedTrusted = isTrustedResolvedComment,
now = Date.now(),
} = options;
let candidate = null;
for (const comment of comments) {
const resolvedMatch = RESOLVED_MARKER_RE.exec(comment.body || '');
if (resolvedMatch && isResolvedTrusted(comment)) {
candidate = null;
continue;
}

const match = MARKER_RE.exec(comment.body || '');
if (!match) continue;
if (!isTrusted(comment)) continue;
const parsed = Date.parse(match[1]);
if (Number.isNaN(parsed) || parsed > now) continue;
return match[1];
candidate = match[1];
}
return null;
return candidate;
}

function gh(args) {
Expand All @@ -113,6 +155,27 @@ export function fetchAllOpenPRs(repo) {
return prs;
}

// Fetches every issue comment on a PR, paginating past the 100-per-page
// cap. Issue comments sort ascending, so on a PR with more than 100
// comments a single unpaginated page can miss the marker entirely if it
// was posted early on -- this walks every page instead.
export function fetchAllIssueComments(repo, number) {
const comments = [];
let page = 1;
const perPage = 100;
for (;;) {
const raw = gh([
'api',
`repos/${repo}/issues/${number}/comments?per_page=${perPage}&page=${page}`,
]);
const batch = JSON.parse(raw);
comments.push(...batch);
if (batch.length < perPage) break;
page += 1;
}
return comments;
}

export function hoursSince(isoString, now = Date.now()) {
return (now - Date.parse(isoString)) / (1000 * 60 * 60);
}
Expand Down Expand Up @@ -176,14 +239,37 @@ async function main() {

const conflicting = await isConflicting(REPO, number);

const commentsRaw = gh([
'api',
`repos/${REPO}/issues/${number}/comments?per_page=100`,
]);
const comments = JSON.parse(commentsRaw);
const comments = fetchAllIssueComments(REPO, number);
const firstObservedAt = findFirstConflictObservedAt(comments);

if (!conflicting) {
if (firstObservedAt) {
console.log(
`PR #${number}: no longer conflicting, clearing stale marker`,
);
if (!DRY_RUN) {
if (labelNames(pr).includes(LABEL)) {
gh([
'pr',
'edit',
String(number),
'--repo',
REPO,
'--remove-label',
LABEL,
]);
}
gh([
'pr',
'comment',
String(number),
'--repo',
REPO,
'--body',
`${RESOLVED_MARKER_PREFIX}${new Date().toISOString()} -->`,
]);
}
}
continue;
}

Expand Down
51 changes: 51 additions & 0 deletions tests/pr-queue-hygiene.test.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,9 @@ import {
isConflicting,
isHeld,
isTrustedMarkerComment,
isTrustedResolvedComment,
MARKER_PREFIX,
RESOLVED_MARKER_PREFIX,
} from '../scripts/pr-queue-hygiene.mjs';

const BOT = { login: 'github-actions[bot]', type: 'Bot' };
Expand All @@ -16,6 +18,10 @@ function marker(timestamp, user = BOT) {
return { body: `${MARKER_PREFIX}${timestamp} -->`, user };
}

function resolvedMarker(timestamp, user = BOT) {
return { body: `${RESOLVED_MARKER_PREFIX}${timestamp} -->`, user };
}

test('findFirstConflictObservedAt: finds the marker comment among others', () => {
const comments = [
{ body: 'unrelated comment', user: HUMAN },
Expand Down Expand Up @@ -77,6 +83,51 @@ test('findFirstConflictObservedAt: tolerates a comment with no author', () => {
);
});

test('findFirstConflictObservedAt: a trusted resolved marker clears an earlier stale marker', () => {
const comments = [
marker('2020-01-01T00:00:00.000Z'),
resolvedMarker('2020-01-02T00:00:00.000Z'),
];
assert.equal(
findFirstConflictObservedAt(comments, {
now: Date.parse('2026-09-03T00:00:00.000Z'),
}),
null,
);
});

test('findFirstConflictObservedAt: a fresh marker after resolution is used, not the pre-resolution one', () => {
const comments = [
marker('2020-01-01T00:00:00.000Z'),
resolvedMarker('2020-01-02T00:00:00.000Z'),
marker('2026-09-01T00:00:00.000Z'),
];
assert.equal(
findFirstConflictObservedAt(comments, {
now: Date.parse('2026-09-03T00:00:00.000Z'),
}),
'2026-09-01T00:00:00.000Z',
);
});

test('findFirstConflictObservedAt: an untrusted resolved marker does not clear the genuine one', () => {
const comments = [
marker('2020-01-01T00:00:00.000Z'),
resolvedMarker('2020-01-02T00:00:00.000Z', HUMAN),
];
assert.equal(
findFirstConflictObservedAt(comments, {
now: Date.parse('2026-09-03T00:00:00.000Z'),
}),
'2020-01-01T00:00:00.000Z',
);
});

test('isTrustedResolvedComment: only an allowlisted bot login is trusted', () => {
assert.equal(isTrustedResolvedComment({ user: BOT }), true);
assert.equal(isTrustedResolvedComment({ user: HUMAN }), false);
});

test('isTrustedMarkerComment: only an allowlisted bot login is trusted', () => {
assert.equal(isTrustedMarkerComment({ user: BOT }), true);
assert.equal(isTrustedMarkerComment({ user: HUMAN }), false);
Expand Down
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