Add syntax check in .py config (#330)

* Add syntax check in .py config

* rename validate

mmcv/utils/config.py

 # Copyright (c) Open-MMLab. All rights reserved.
+import ast
 import os.path as osp
 import shutil
 import sys
@@ -80,6 +81,16 @@ class Config(object):
 
     """
 
+    @staticmethod
+    def _validate_py_syntax(filename):
+        with open(filename) as f:
+            content = f.read()
+        try:
+            ast.parse(content)
+        except SyntaxError:
+            raise SyntaxError('There are syntax errors in config '
+                              f'file {filename}')
+
     @staticmethod
     def _file2dict(filename):
         filename = osp.abspath(osp.expanduser(filename))
@@ -93,6 +104,7 @@ class Config(object):
                                 osp.join(temp_config_dir, temp_config_name))
                 temp_module_name = osp.splitext(temp_config_name)[0]
                 sys.path.insert(0, temp_config_dir)
+                Config._validate_py_syntax(filename)
                 mod = import_module(temp_module_name)
                 sys.path.pop(0)
                 cfg_dict = {

tests/test_config.py

@@ -272,3 +272,17 @@ def test_reserved_key():
     cfg_file = osp.join(osp.dirname(__file__), 'data/config/g.py')
     with pytest.raises(KeyError):
         Config.fromfile(cfg_file)
+
+
+def test_syntax_error():
+    temp_cfg_file = tempfile.NamedTemporaryFile(suffix='.py')
+    temp_cfg_path = temp_cfg_file.name
+    # write a file with syntax error
+    with open(temp_cfg_path, 'w') as f:
+        f.write('a=0b=dict(c=1)')
+    with pytest.raises(
+            SyntaxError,
+            match='There are syntax errors in config '
+            f'file {temp_cfg_path}'):
+        Config.fromfile(temp_cfg_path)
+    temp_cfg_file.close()