fix: name a missing database in one error line

scripts/common.py

@@ -31,10 +31,30 @@ except ImportError:
 
 
 
+class DatabaseUnreadable(FileNotFoundError):
+    """The database a command was pointed at does not exist or is not JSON."""
+
+
 def load_database(db_path: str) -> dict:
-    """Load database.json and return parsed dict."""
-    with open(db_path) as f:
-        return json.load(f)
+    """Load database.json and return parsed dict.
+
+    A missing or damaged file raises DatabaseUnreadable, which run_cli turns
+    into one line saying how to build it: `--db nosuch.json` ended at the
+    bottom of a stack trace.
+    """
+    try:
+        with open(db_path) as f:
+            return json.load(f)
+    except FileNotFoundError:
+        raise DatabaseUnreadable(
+            f"{db_path} not found. Build it with: python scripts/generate_db.py "
+            "--force --bios-dir bios --output database.json"
+        ) from None
+    except json.JSONDecodeError as exc:
+        raise DatabaseUnreadable(
+            f"{db_path} is not valid JSON ({exc}). Rebuild it with: "
+            "python scripts/generate_db.py --force --bios-dir bios --output database.json"
+        ) from None
 
 
 
@@ -2501,6 +2521,9 @@ def run_cli(main: Callable[[], int | None]) -> None:
     try:
         code = main()
         sys.stdout.flush()
+    except DatabaseUnreadable as exc:
+        print(f"ERROR: {exc}", file=sys.stderr)
+        sys.exit(1)
     except BrokenPipeError:
         os.dup2(os.open(os.devnull, os.O_WRONLY), sys.stdout.fileno())
         sys.exit(141)

scripts/generate_pack.py

@@ -2426,8 +2426,7 @@ def _run_verify_packs(args: argparse.Namespace) -> None:
     second implementation here answered a narrower one and reported OK while
     the core extras went unchecked.
     """
-    with open(args.db) as f:
-        verify_db = json.load(f)
+    verify_db = load_database(args.db)
 
     if args.platform:
         platforms = [args.platform]

scripts/generate_truth.py

@@ -78,8 +78,9 @@ def main(argv: list[str] | None = None) -> None:
     profiles = load_emulator_profiles(args.emulators_dir)
 
     # Load database (optional)
+    # The default may be absent; a --db that was named must exist.
     db: dict | None = None
-    if os.path.exists(args.db):
+    if args.db != DEFAULT_DB_FILE or os.path.exists(args.db):
         db = load_database(args.db)
 
     # Determine platforms

scripts/slots.py

@@ -807,6 +807,7 @@ def main() -> int:
 
     from common import (
         list_registered_platforms,
+        load_database,
         load_emulator_profiles,
         load_platform_config,
         require_platform,
@@ -830,8 +831,7 @@ def main() -> int:
     )
     args = parser.parse_args()
 
-    with open(args.db, encoding="utf-8") as handle:
-        db = json.load(handle)
+    db = load_database(args.db)
     profiles = load_emulator_profiles(args.emulators_dir)
     if args.platform:
         require_platform(args.platform, args.platforms_dir)

scripts/validate_pr.py

@@ -326,13 +326,15 @@ def _files_to_validate(
 
 
 def _load_database_if_any(path: str) -> dict | None:
-    try:
-        return load_database(path)
-    except FileNotFoundError:
-        return None
-    except json.JSONDecodeError as e:
-        print(f"WARNING: corrupt database.json: {e}", file=sys.stderr)
+    """The database, optional only where the default is meant.
+
+    A mistyped --db read as "no database" and every file passed its
+    duplicate and placement checks unchecked; a damaged one did the same
+    after a warning.
+    """
+    if path == DEFAULT_DB and not os.path.exists(path):
         return None
+    return load_database(path)
 
 
 def main() -> None:

scripts/verify.py

@@ -56,6 +56,7 @@ from common import (
     list_emulator_profiles,
     list_system_ids,
     load_data_dir_registry,
+    load_database,
     load_emulator_profiles,
     load_platform_config,
     md5sum,
@@ -2178,8 +2179,7 @@ def _main(held: contextlib.ExitStack) -> None:
 
     hold_data_dirs(held, load_data_dir_registry(args.platforms_dir))
 
-    with open(args.db) as f:
-        db = json.load(f)
+    db = load_database(args.db)
 
     # Emulator mode
     if args.emulator:

tests/test_system_selection.py

@@ -171,6 +171,43 @@ class CrossReferenceAnswersForTheEmulatorAsked(unittest.TestCase):
         self.assertIn("not run by misterfpga", proc.stderr)
 
 
+class AMissingDatabaseIsNamed(unittest.TestCase):
+    """`slots.py --db nosuch.json` and `verify.py --all --db nosuch.json`
+    ended on a FileNotFoundError at the bottom of a stack trace;
+    generate_truth and validate_pr carried on without one."""
+
+    EXTRA = {
+        "auto_fetch.py": ["--all", "--dry-run"],
+        "generate_truth.py": ["--all", "--output-dir", "{out}"],
+        "generate_site.py": ["--docs-dir", "{out}"],
+        "generate_pack.py": ["--platform", "retroarch", "--offline", "--output-dir", "{out}"],
+        "validate_pr.py": ["bios/Sony/PlayStation/scph5501.bin"],
+        "verify.py": ["--all"],
+    }
+
+    def _taking_db(self) -> list[str]:
+        return sorted(
+            path.name for path in (REPO_ROOT / "scripts").glob("*.py")
+            if re.search(r'add_argument\(\s*"--db"', path.read_text(encoding="utf-8"))
+        )
+
+    def test_every_script_names_the_missing_file(self):
+        scratch = tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp")
+        self.addCleanup(scratch.cleanup)
+        out = str(Path(scratch.name) / "out")
+        for script in self._taking_db():
+            extra = [arg.format(out=out) for arg in self.EXTRA.get(script, [])]
+            with self.subTest(script=script):
+                proc = subprocess.run(
+                    [sys.executable, f"scripts/{script}", "--db", "nosuch.json", *extra],
+                    capture_output=True, text=True, cwd=str(REPO_ROOT), timeout=600,
+                    check=False,
+                )
+                self.assertNotEqual(proc.returncode, 0, proc.stdout[-500:])
+                self.assertNotIn("Traceback", proc.stderr, proc.stderr[-1500:])
+                self.assertIn("nosuch.json", proc.stderr)
+
+
 class StrictVerifyFailsOnACriticalMiss(unittest.TestCase):
     """verify exited 0 with a required file missing on an md5 platform, so
     the pipeline printed "verify OK" over a pack the frontend rejects."""