[Perf] Validate @config in pre-commit instead of dynamically (#20200)

Signed-off-by: Lionel Villard <villard@us.ibm.com>

tests/tools/test_config_validator.py

@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import ast
+
+import pytest
+
+from tools.validate_config import validate_ast
+
+_TestConfig1 = '''
+@config
+class _TestConfig1:
+    pass
+'''
+
+_TestConfig2 = '''
+@config
+@dataclass
+class _TestConfig2:
+    a: int
+    """docstring"""
+'''
+
+_TestConfig3 = '''
+@config
+@dataclass
+class _TestConfig3:
+    a: int = 1
+'''
+
+_TestConfig4 = '''
+@config
+@dataclass
+class _TestConfig4:
+    a: Union[Literal[1], Literal[2]] = 1
+    """docstring"""
+'''
+
+
+@pytest.mark.parametrize(("test_config", "expected_error"), [
+    (_TestConfig1, "must be a dataclass"),
+    (_TestConfig2, "must have a default"),
+    (_TestConfig3, "must have a docstring"),
+    (_TestConfig4, "must use a single Literal"),
+])
+def test_config(test_config, expected_error):
+    tree = ast.parse(test_config)
+    with pytest.raises(Exception, match=expected_error):
+        validate_ast(tree)