Fix: Handle Trailing Commas and Empty Strings in File Paths

mypy/config_parser.py

@@ -109,6 +109,9 @@ def split_and_match_files_list(paths: Sequence[str]) -> list[str]:
     expanded_paths = []
 
     for path in paths:
+        if not path:
+            continue
+
         path = expand_path(path.strip())
         globbed_files = fileglob.glob(path, recursive=True)
         if globbed_files:
@@ -318,6 +321,23 @@ def parse_config_file(
             print(f"{file_read}: No [mypy] section in config file", file=stderr)
     else:
         section = parser["mypy"]
+
+        if "files" in section:
+            raw_files = section["files"].strip()
+            files_split = [file.strip() for file in raw_files.split(",")]
+
+            # Remove trailing empty entry if present
+            if files_split and files_split[-1] == "":
+                files_split.pop()
+
+            # Raise an error if there are any remaining empty strings
+            if "" in files_split:
+                raise ValueError(
+                    "Invalid config: Empty filenames are not allowed except for trailing commas."
+                )
+
+            options.files = files_split
+
         prefix = f"{file_read}: [mypy]: "
         updates, report_dirs = parse_section(
             prefix, options, set_strict_flags, section, config_types, stderr

mypy/test/testconfigparser.py

@@ -0,0 +1,168 @@
+import os
+import tempfile
+from unittest import TestCase, main
+
+from mypy.config_parser import parse_config_file
+from mypy.options import Options
+
+
+class TestConfigParser(TestCase):
+    def test_parse_config_file_with_single_file(self) -> None:
+        """A single file should be correctly parsed."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files = file1.py
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, ["file1.py"])
+
+    def test_parse_config_file_with_no_spaces(self) -> None:
+        """Files listed without spaces should be correctly parsed."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files =file1.py,file2.py,file3.py
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, ["file1.py", "file2.py", "file3.py"])
+
+    def test_parse_config_file_with_extra_spaces(self) -> None:
+        """Files with extra spaces should be correctly parsed."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files =  file1.py ,   file2.py  ,   file3.py
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, ["file1.py", "file2.py", "file3.py"])
+
+    def test_parse_config_file_with_empty_files_key(self) -> None:
+        """An empty files key should result in an empty list."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files =
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, [])
+
+    def test_parse_config_file_with_only_comma(self) -> None:
+        """A files key with only a comma should raise an error."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files = ,
+                    """
+                )
+
+            options = Options()
+
+            with self.assertRaises(ValueError) as cm:
+                parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertIn("Invalid config", str(cm.exception))
+
+    def test_parse_config_file_with_only_whitespace(self) -> None:
+        """A files key with only whitespace should result in an empty list."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files =
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, [])
+
+    def test_parse_config_file_with_mixed_valid_and_invalid_entries(self) -> None:
+        """Mix of valid and invalid filenames should raise an error."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files = file1.py, , , file2.py
+                    """
+                )
+
+            options = Options()
+
+            with self.assertRaises(ValueError) as cm:
+                parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertIn("Invalid config", str(cm.exception))
+
+    def test_parse_config_file_with_newlines_between_files(self) -> None:
+        """Newlines between file entries should be correctly handled."""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            config_path = os.path.join(tmpdirname, "test_config.ini")
+
+            with open(config_path, "w") as f:
+                f.write(
+                    """
+                    [mypy]
+                    files = file1.py,
+                            file2.py,
+                            file3.py
+                    """
+                )
+
+            options = Options()
+
+            parse_config_file(options, lambda: None, config_path, stdout=None, stderr=None)
+
+            self.assertEqual(options.files, ["file1.py", "file2.py", "file3.py"])
+
+
+if __name__ == "__main__":
+    main()