fix(ci): let the PR labeler actually write labels (#566)

* fix(ci): let the PR labeler actually write labels

* test(ci): pin the labeler to the permissions the API demands

Author: lidge-jun

.github/scripts/pr-labeler.test.cjs

@@ -165,8 +165,15 @@ describe("pr-labeler workflow", () => {
   it("keeps trusted default-branch checkout, concurrency cancel, and minimal permissions", () => {
     assert.match(workflow, /ref:\s*\$\{\{\s*github\.event\.repository\.default_branch\s*\}\}/);
     assert.match(workflow, /cancel-in-progress:\s*true/);
-    assert.match(workflow, /pull-requests:\s*read/);
     assert.match(workflow, /issues:\s*write/);
-    assert.doesNotMatch(workflow, /pull-requests:\s*write/);
+    // The issues label endpoints are shared with pull requests: writing a label
+    // onto a PR number needs pull_requests=write alongside issues=write, which
+    // GitHub reports as `issues=write; pull_requests=write`. Pinning this to
+    // read made the workflow fail closed on the first PR that actually needed a
+    // label applied (#565), so write is the minimum here, not an escalation.
+    assert.match(workflow, /pull-requests:\s*write/);
+    // contents stays read — the labeler never pushes.
+    assert.match(workflow, /contents:\s*read/);
+    assert.doesNotMatch(workflow, /contents:\s*write/);
   });
 });

.github/workflows/pr-labeler.yml

@@ -17,8 +17,14 @@ concurrency:
 
 permissions:
   contents: read
-  # pulls.get only needs read; label mutations use the issues API.
-  pull-requests: read
+  # pulls.get only needs read, but the issues label endpoints are shared with
+  # pull requests: adding or removing a label on a PR number is rejected with
+  # "Resource not accessible by integration" unless the token also carries
+  # pull_requests=write (the API reports `issues=write; pull_requests=write`
+  # in x-accepted-github-permissions). Read-only here silently worked while
+  # every run happened to be a no-op sync, and failed on the first PR that
+  # actually needed a label written.
+  pull-requests: write
   issues: write
 
 jobs: