fix(watch-pr): keep stack parents beyond the first 300 open PRs

pstack/skills/poteto-mode/scripts/watch-pr/github.ts

@@ -489,20 +489,29 @@ export class GhGitHubReader implements T.GitHubReader {
   async openPullRequests(
     repository: T.Repository
   ): Promise<readonly T.OpenPullRequest[]> {
-    const value = await runJson([
-      "gh",
-      "pr",
-      "list",
-      "--repo",
-      `${repository.owner}/${repository.repo}`,
-      "--state",
-      "open",
-      "--limit",
-      "300",
-      "--json",
-      "number,headRefName,baseRefName,isCrossRepository",
-    ]);
-    return list(value, "open PRs").map((item, index) => {
+    // gh lists the newest PRs first and stops at --limit, so a full page may
+    // have cut off an older stack parent. Ask again until the list is short.
+    let value: readonly unknown[];
+    for (let limit = 300; ; limit *= 2) {
+      value = list(
+        await runJson([
+          "gh",
+          "pr",
+          "list",
+          "--repo",
+          `${repository.owner}/${repository.repo}`,
+          "--state",
+          "open",
+          "--limit",
+          String(limit),
+          "--json",
+          "number,headRefName,baseRefName,isCrossRepository",
+        ]),
+        "open PRs"
+      );
+      if (value.length < limit) break;
+    }
+    return value.map((item, index) => {
       const object = record(item, `open PRs[${index}]`);
       if (typeof object.isCrossRepository !== "boolean")
         missing(`open PRs[${index}].isCrossRepository`, object.isCrossRepository);

pstack/skills/poteto-mode/scripts/watch-pr/open-pulls.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "bun:test";
+import { spawnSync } from "node:child_process";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+describe("open pull request discovery", () => {
+  it("keeps a stack parent that is older than the first 300 open PRs", () => {
+    const directory = mkdtempSync(join(tmpdir(), "watch-pr-open-pulls-"));
+    try {
+      // Like gh, the fake returns the newest open PRs first and stops at --limit.
+      writeFileSync(
+        join(directory, "gh"),
+        `#!${process.execPath}
+const args = process.argv.slice(2);
+const limit = Number(args[args.indexOf("--limit") + 1]);
+const rows = [];
+for (let number = 400; number > 1; number -= 1)
+  rows.push({ number, headRefName: "other-" + number, baseRefName: "main", isCrossRepository: false });
+rows[0] = { number: 400, headRefName: "feature", baseRefName: "base-feature", isCrossRepository: false };
+rows.push({ number: 1, headRefName: "base-feature", baseRefName: "main", isCrossRepository: false });
+console.log(JSON.stringify(rows.slice(0, limit)));
+`,
+        { mode: 0o755 }
+      );
+      const program = `import { GhGitHubReader, discoverStack } from ${JSON.stringify(import.meta.dir + "/github.ts")};
+        const stack = await discoverStack(new GhGitHubReader(), { owner: "owner", repo: "repo", number: 400 });
+        console.log(JSON.stringify(stack.map((item) => item.number)));`;
+      const child = spawnSync(process.execPath, ["-e", program], {
+        encoding: "utf8",
+        timeout: 5000,
+        env: { ...process.env, PATH: directory + ":" + process.env.PATH },
+      });
+      expect(child.error).toBeUndefined();
+      expect(child.status).toBe(0);
+      expect(JSON.parse(child.stdout)).toEqual([1, 400]);
+    } finally {
+      rmSync(directory, { recursive: true, force: true });
+    }
+  });
+});