fix: fail a named pack that is not built

scripts/generate_pack.py

@@ -2468,12 +2468,17 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
     for platform_name in platforms:
         found = sorted(expected[platform_name] & on_disk)
         if not found:
-            print(f"  {platform_name}: SKIP (no pack in {args.output_dir})")
-            # Naming a platform is asking about its pack. Answering SKIP and
-            # exiting 0 says the pack passed; with --all, a platform whose pack
-            # was not built is genuinely out of scope.
+            # Naming a platform is asking about its pack: FAIL, with the
+            # command that builds it. With --all, a platform whose pack was
+            # not built is out of scope and skipped.
             if args.platform:
+                print(
+                    f"  {platform_name}: FAIL (no pack in {args.output_dir}; build it with "
+                    f"generate_pack.py --platform {platform_name} --output-dir {args.output_dir})"
+                )
                 all_ok = False
+            else:
+                print(f"  {platform_name}: SKIP (no pack in {args.output_dir})")
             continue
         tc = _target_cores_for(platform_name, args.target, args.platforms_dir)
         # A group pack and a pack built for the platform alone can both be

tests/test_audit_regressions.py

@@ -4951,5 +4951,22 @@ class ATargetIsNamedWhenItRemovesTheCore(unittest.TestCase):
         self.assertNotIn("is not run by", result.stderr)
 
 
+
+class ANamedPackThatIsAbsentFails(unittest.TestCase):
+    """--verify-packs --platform retroarch on an empty directory printed
+    "SKIP" and exited 1: a skip label on a failure, and no next step."""
+
+    def test_the_line_says_fail_and_how_to_build(self):
+        with tempfile.TemporaryDirectory(dir=TMP_ROOT) as directory:
+            result = subprocess.run(
+                [sys.executable, "scripts/generate_pack.py", "--platform", "retroarch",
+                 "--verify-packs", "--output-dir", directory],
+                cwd=ROOT, capture_output=True, text=True, timeout=600,
+            )
+        self.assertEqual(result.returncode, 1)
+        self.assertIn("retroarch: FAIL (no pack in", result.stdout)
+        self.assertIn("generate_pack.py --platform retroarch", result.stdout)
+
+
 if __name__ == "__main__":
     unittest.main()