refactor: extract isRateLimitError helper into error_helpers.cjs

Move the rate limit detection regex into a dedicated isRateLimitError()
helper in error_helpers.cjs, following the same pattern as isLockedError().
Update check_skip_if_check_failing.cjs to use the helper.
Add tests for isRateLimitError in error_helpers.test.cjs.

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/294a40fd-3964-43aa-a722-81fbd321cd18

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: Copilot

actions/setup/js/check_skip_if_check_failing.cjs

@@ -1,7 +1,7 @@
 // @ts-check
 /// <reference types="@actions/github-script" />
 
-const { getErrorMessage } = require("./error_helpers.cjs");
+const { getErrorMessage, isRateLimitError } = require("./error_helpers.cjs");
 const { ERR_API } = require("./error_codes.cjs");
 const { getBaseBranch } = require("./get_base_branch.cjs");
 
@@ -217,7 +217,7 @@ async function main() {
     // due to transient GitHub API availability issues. When multiple workflows run
     // simultaneously, they can exhaust the installation API rate limit, causing this
     // check to fail. Failing open matches the behavior of other pre-activation checks.
-    if (/\bapi rate limit\b|\brate limit exceeded\b/i.test(errorMsg)) {
+    if (isRateLimitError(error)) {
       core.warning(`⚠️ API rate limit exceeded while checking CI status for ref "${ref}": ${errorMsg}`);
       core.warning(`Allowing workflow to proceed (fail-open on rate limit)`);
       core.setOutput("skip_if_check_failing_ok", "true");

actions/setup/js/error_helpers.cjs

@@ -40,4 +40,18 @@ function isLockedError(error) {
   return hasLockedMessage;
 }
 
-module.exports = { getErrorMessage, isLockedError };
+/**
+ * Check if an error is due to a GitHub API rate limit being exceeded.
+ * This includes both installation-level and user-level rate limits.
+ * Used to determine if a check should fail-open (allow workflow to proceed)
+ * rather than hard-failing when the error is transient.
+ *
+ * @param {unknown} error - The error value to check
+ * @returns {boolean} True if error is due to API rate limiting, false otherwise
+ */
+function isRateLimitError(error) {
+  const errorMessage = getErrorMessage(error);
+  return /\bapi rate limit\b|\brate limit exceeded\b/i.test(errorMessage);
+}
+
+module.exports = { getErrorMessage, isLockedError, isRateLimitError };

actions/setup/js/error_helpers.test.cjs

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "vitest";
-import { getErrorMessage, isLockedError } from "./error_helpers.cjs";
+import { getErrorMessage, isLockedError, isRateLimitError } from "./error_helpers.cjs";
 
 describe("error_helpers", () => {
   describe("getErrorMessage", () => {
@@ -89,4 +89,35 @@ describe("error_helpers", () => {
       expect(isLockedError(error)).toBe(true);
     });
   });
+
+  describe("isRateLimitError", () => {
+    it("should return true for 'API rate limit exceeded' message", () => {
+      expect(isRateLimitError(new Error("API rate limit exceeded for installation"))).toBe(true);
+    });
+
+    it("should return true for 'rate limit exceeded' message", () => {
+      expect(isRateLimitError(new Error("rate limit exceeded: please retry after 60 seconds"))).toBe(true);
+    });
+
+    it("should return true for mixed-case 'API Rate Limit' message", () => {
+      expect(isRateLimitError(new Error("API Rate Limit exceeded"))).toBe(true);
+    });
+
+    it("should return false for unrelated API errors", () => {
+      expect(isRateLimitError(new Error("Network connection error"))).toBe(false);
+    });
+
+    it("should return false for null error", () => {
+      expect(isRateLimitError(null)).toBe(false);
+    });
+
+    it("should return false for undefined error", () => {
+      expect(isRateLimitError(undefined)).toBe(false);
+    });
+
+    it("should return false for non-rate-limit 403 errors", () => {
+      const error = new Error("Forbidden: insufficient permissions");
+      expect(isRateLimitError(error)).toBe(false);
+    });
+  });
 });