fix: resolve maintainers from repository root

tools/get_maintainer.py

@@ -27,11 +27,12 @@
 
 import sys
 import os
+from pathlib import Path
 
-MAINTAINERS_FILE = "MAINTAINERS"
+MAINTAINERS_FILE = Path(__file__).resolve().parent.parent / "MAINTAINERS"
 
 if not os.path.exists(MAINTAINERS_FILE):
-    print("Error: MAINTAINERS file not found.")
+    print(f"Error: MAINTAINERS file not found at {MAINTAINERS_FILE}.")
     sys.exit(1)
 
 if len(sys.argv) < 2:

tools/test_get_maintainer.py

@@ -0,0 +1,29 @@
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parent.parent
+SCRIPT = ROOT / "tools" / "get_maintainer.py"
+
+
+class TestGetMaintainer(unittest.TestCase):
+    def test_invocation_outside_repository_root(self):
+        with tempfile.TemporaryDirectory() as cwd:
+            result = subprocess.run(
+                [sys.executable, str(SCRIPT), "front/parser/ast.rs"],
+                cwd=cwd,
+                capture_output=True,
+                text=True,
+                check=False,
+            )
+
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("Maintainers to CC:", result.stdout)
+        self.assertNotIn("MAINTAINERS file not found", result.stdout)
+
+
+if __name__ == "__main__":
+    unittest.main()