fix: check --target before the output lock

A mistyped target waited on the dist lock and the data directory refresh
before it was refused (finding 62).

scripts/generate_pack.py

@@ -3477,6 +3477,22 @@ def _main(held: contextlib.ExitStack) -> None:
         parser.error("Specify --platform or --all")
         return
 
+    # A mistyped target is refused before the output lock and the data
+    # directory refresh: checked after them, `--target swich` waited on a
+    # pipeline's caches before saying the target does not exist.
+    target_cores_cache: dict[str, set[str] | None] = {}
+    if args.target:
+        try:
+            target_cores_cache, platforms = build_target_cores_cache(
+                platforms,
+                args.target,
+                args.platforms_dir,
+                is_all=args.all,
+            )
+        except (FileNotFoundError, ValueError) as e:
+            print(f"ERROR: {e}", file=sys.stderr)
+            sys.exit(1)
+
     data_registry = load_data_dir_registry(args.platforms_dir)
     # The output directory is claimed before the data directory refresh: a
     # refresh waits for every run that holds a cache, so a second build
@@ -3498,19 +3514,6 @@ def _main(held: contextlib.ExitStack) -> None:
 
         emu_profiles = load_emulator_profiles(args.emulators_dir)
 
-        target_cores_cache: dict[str, set[str] | None] = {}
-        if args.target:
-            try:
-                target_cores_cache, platforms = build_target_cores_cache(
-                    platforms,
-                    args.target,
-                    args.platforms_dir,
-                    is_all=args.all,
-                )
-            except (FileNotFoundError, ValueError) as e:
-                print(f"ERROR: {e}", file=sys.stderr)
-                sys.exit(1)
-
         groups = group_identical_platforms(
             platforms, args.platforms_dir, target_cores_cache if args.target else None
         )

tests/test_target_verify.py

@@ -58,5 +58,32 @@ class ANameClaimsOnlyANarrowingThatHappened(unittest.TestCase):
         )
 
 
+class AMistypedTargetIsRefusedFirst(unittest.TestCase):
+    """`--platform retroarch --target swich` took the dist lock and waited on
+    the data directory refresh, 22 s here and hours behind a pipeline, before
+    saying the target does not exist."""
+
+    def test_no_lock_and_no_refresh_before_the_refusal(self):
+        from unittest import mock
+
+        import generate_pack
+
+        def touched(*_a, **_kw):
+            raise AssertionError("lock or refresh taken before the target check")
+
+        argv = ["generate_pack.py", "--platform", "retroarch", "--target", "swich",
+                "--output-dir", str(REPO_ROOT / "tmp" / "never-written")]
+        err = io.StringIO()
+        with mock.patch.object(sys, "argv", argv), \
+                mock.patch.object(generate_pack, "_pack_output_lock", touched), \
+                mock.patch.object(generate_pack, "hold_data_dirs", touched), \
+                contextlib.redirect_stdout(io.StringIO()), \
+                contextlib.redirect_stderr(err), \
+                self.assertRaises(SystemExit) as ctx:
+            generate_pack.main()
+        self.assertEqual(ctx.exception.code, 1)
+        self.assertIn("Unknown target 'swich'", err.getvalue())
+
+
 if __name__ == "__main__":
     unittest.main()