fix(review): paginate check-runs in findPreviewUrlFromChecks (#7881)

findPreviewUrlFromChecks fetched only page 1 of a head SHA's check-runs
(?per_page=100) and never followed pagination, while its two siblings in the
same file -- getPreviewBuildState and findPreviewUrlFromPrComments -- already
walk this identical endpoint via findAcrossPages. The file's own header comment
reasons about exactly this failure: a commit with >100 check-runs pushes the
Cloudflare Workers Builds check-run onto page 2+, and a page-1-only read then
returns null as if the preview didn't exist -- so the PR comment shows a
permanent loading spinner even though the deploy succeeded.

Route the check-runs fetch through findAcrossPages, reusing the exact pattern
getPreviewBuildState already applies to this endpoint (no new pagination loop);
the per-run preview-URL scan moves into the page probe unchanged.

Adds regression tests: a preview check-run on page 2 is still found (asserting
the walk reaches page 2), a page-1 hit takes no extra request, a failed
check-run is skipped, and an all-next-Link/no-check_runs response terminates
bounded at null.

Closes #7779

Co-authored-by: davion-knight <marko.j0158@gmail.com>

Author: davion-knight

src/review/visual/preview-url.ts

@@ -243,15 +243,24 @@ export async function findPreviewUrlFromChecks(params: {
       const url = extractPreviewUrl(status.target_url);
       if (url) return url;
     }
-    const checks = await githubJson<{ check_runs?: Array<{ status?: string; conclusion?: string; details_url?: string; output?: { summary?: string; text?: string } }> }>(
+    // Walk every page of check-runs (#7779): a head SHA with >100 check-runs can push the Cloudflare Workers
+    // Builds check-run onto page 2+, and a page-1-only read would then miss it -- the same failure the file's
+    // header reasons about, already handled by getPreviewBuildState/findPreviewUrlFromPrComments for this
+    // identical endpoint via findAcrossPages.
+    const checkUrl = await findAcrossPages<{ status?: string; conclusion?: string; details_url?: string; output?: { summary?: string; text?: string } }, string>(
       `${base}/commits/${encodeURIComponent(params.sha)}/check-runs?per_page=100`,
       opts,
-    ).catch(() => null);
-    for (const run of checks?.check_runs ?? []) {
-      if (run.status === "completed" && run.conclusion && run.conclusion !== "success") continue;
-      const url = extractPreviewUrl(run.details_url) ?? extractPreviewUrl(run.output?.summary) ?? extractPreviewUrl(run.output?.text);
-      if (url) return url;
-    }
+      (payload) => (payload as { check_runs?: Array<{ status?: string; conclusion?: string; details_url?: string; output?: { summary?: string; text?: string } }> })?.check_runs ?? [],
+      (runs) => {
+        for (const run of runs) {
+          if (run.status === "completed" && run.conclusion && run.conclusion !== "success") continue;
+          const url = extractPreviewUrl(run.details_url) ?? extractPreviewUrl(run.output?.summary) ?? extractPreviewUrl(run.output?.text);
+          if (url) return url;
+        }
+        return null;
+      },
+    );
+    if (checkUrl) return checkUrl;
   } catch (error) {
     console.log(JSON.stringify({ event: "preview_from_checks_error", repo: `${params.repo.owner}/${params.repo.repo}`, message: String(error).slice(0, 200) }));
   }

test/unit/preview-url.test.ts

@@ -1,6 +1,6 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { clearGitHubResponseCacheForTest, githubRateLimitAdmissionKeyForInstallation, latestGitHubRestRateLimitObservation } from "../../src/github/client";
-import { extractPreviewUrl, findPreviewUrlFromPrComments, getLatestDeploymentStatus, getPreviewBuildState } from "../../src/review/visual/preview-url";
+import { extractPreviewUrl, findPreviewUrlFromChecks, findPreviewUrlFromPrComments, getLatestDeploymentStatus, getPreviewBuildState } from "../../src/review/visual/preview-url";
 
 /** GitHub's `Link` header for a page that advertises a next page (the exact shape findAcrossPages walks). */
 const NEXT_LINK = '<https://api.github.com/resource?per_page=100&page=99>; rel="next", <https://api.github.com/resource?per_page=100&page=99>; rel="last"';
@@ -52,6 +52,57 @@ describe("preview-url GitHub reads", () => {
   });
 });
 
+describe("findPreviewUrlFromChecks pagination (#7779)", () => {
+  const isStatus = (input: RequestInfo | URL) => /\/status\b/.test(String(input));
+  const isCheckRuns = (input: RequestInfo | URL) => /\/check-runs\b/.test(String(input));
+
+  it("follows Link: rel=next and finds a preview check-run on page 2", async () => {
+    // Page 1 carries only an unrelated check-run; the Cloudflare Workers Builds check-run (with the preview
+    // link) is on page 2 -- the exact >100-check-runs case a page-1-only read used to miss.
+    const fetchMock = vi.fn(async (input: RequestInfo | URL) => {
+      if (isStatus(input)) return Response.json({ statuses: [] });
+      if (isCheckRuns(input) && isPage2(input)) {
+        return Response.json({ check_runs: [{ status: "completed", conclusion: "success", details_url: "https://pr-1.app.workers.dev" }] });
+      }
+      // page 1: an unrelated passing check with no preview link, advertising a next page
+      return Response.json({ check_runs: [{ status: "completed", conclusion: "success", details_url: "https://ci.example.com/run/1" }] }, { headers: { link: NEXT_LINK } });
+    });
+    vi.stubGlobal("fetch", fetchMock);
+
+    await expect(findPreviewUrlFromChecks({ token: "t", repo: REPO, sha: "abc123" })).resolves.toBe("https://pr-1.app.workers.dev");
+    // Proves it actually walked to page 2 (the whole point of the fix) rather than stopping at page 1.
+    expect(fetchMock.mock.calls.some((c) => isCheckRuns(c[0] as RequestInfo | URL) && isPage2(c[0] as RequestInfo | URL))).toBe(true);
+  });
+
+  it("returns null when every page advertises more but none carries check_runs (bounded walk)", async () => {
+    // Payloads with no `check_runs` field exercise the empty-page fallback; the always-next Link can't loop
+    // unboundedly (findAcrossPages caps the walk), so this resolves to null instead of hanging.
+    const fetchMock = vi.fn(async (input: RequestInfo | URL) => {
+      if (isStatus(input)) return Response.json({ statuses: [] });
+      return Response.json({}, { headers: { link: NEXT_LINK } });
+    });
+    vi.stubGlobal("fetch", fetchMock);
+
+    await expect(findPreviewUrlFromChecks({ token: "t", repo: REPO, sha: "abc123" })).resolves.toBeNull();
+  });
+
+  it("skips a failed check-run and still finds the preview link on page 1 without an extra request", async () => {
+    const fetchMock = vi.fn(async (input: RequestInfo | URL) => {
+      if (isStatus(input)) return Response.json({ statuses: [] });
+      return Response.json({
+        check_runs: [
+          { status: "completed", conclusion: "failure", details_url: "https://pr-9.app.workers.dev" }, // failed → skipped, its URL must NOT win
+          { status: "completed", conclusion: "success", details_url: "https://pr-real.app.workers.dev" },
+        ],
+      });
+    });
+    vi.stubGlobal("fetch", fetchMock);
+
+    await expect(findPreviewUrlFromChecks({ token: "t", repo: REPO, sha: "abc123" })).resolves.toBe("https://pr-real.app.workers.dev");
+    expect(fetchMock.mock.calls.some((c) => isPage2(c[0] as RequestInfo | URL))).toBe(false);
+  });
+});
+
 describe("preview-url pagination (#7450)", () => {
   it("findPreviewUrlFromPrComments follows Link: rel=next and finds the bot comment on page 2", async () => {
     const page1 = Array.from({ length: 100 }, (_v, i) => ({ user: { login: `user${i}` }, body: "just chatter" }));