feat: strip trailing whitespace in EditFile and WriteFile tools

Modify the EditFile and WriteFile tools so that they always strip trailing whitespace for each line from the text content to be written from the LLM.

```git-revs
49e2dec  (Base revision)
d9b5330  Strip trailing whitespace from each line before writing to file
4fd7add  Update docstring to mention trailing whitespace removal
1a7d7c6  Add test for trailing whitespace stripping in WriteFile and EditFile
0b57f3d  Update test to match actual behavior without trailing newline
74e7013  Fix empty lines test expectation
4e9026a  Fix third test expectation
f315fae  Auto-commit format changes
HEAD     Auto-commit lint changes
```

codemcp-id: 234-feat-strip-trailing-whitespace-in-editfile-and-wri
ghstack-source-id: a8d9190
Pull-Request-resolved: #224

Author: ezyang

codemcp/file_utils.py

@@ -164,6 +164,7 @@ async def write_text_content(
     line_endings: Optional[str] = None,
 ) -> None:
     """Write text content to a file with specified encoding and line endings.
+    Automatically strips trailing whitespace from each line.
 
     Args:
         file_path: The path to the file
@@ -181,8 +182,13 @@ async def write_text_content(
     # First normalize content to LF line endings
     normalized_content = normalize_to_lf(content)
 
+    # Strip trailing whitespace from each line
+    stripped_content = "\n".join(
+        line.rstrip() for line in normalized_content.splitlines()
+    )
+
     # Apply the requested line ending
-    final_content = apply_line_endings(normalized_content, line_endings)
+    final_content = apply_line_endings(stripped_content, line_endings)
 
     # Ensure directory exists
     ensure_directory_exists(file_path)

e2e/test_trailing_whitespace.py

@@ -0,0 +1,179 @@
+#!/usr/bin/env python3
+
+"""Tests for trailing whitespace stripping in the WriteFile and EditFile subtools."""
+
+import os
+import unittest
+
+from codemcp.testing import MCPEndToEndTestCase
+
+
+class TrailingWhitespaceTest(MCPEndToEndTestCase):
+    """Test that trailing whitespace is properly stripped when using WriteFile and EditFile."""
+
+    async def test_write_file_strips_trailing_whitespace(self):
+        """Test that the WriteFile subtool strips trailing whitespace from each line."""
+        test_file_path = os.path.join(self.temp_dir.name, "write_whitespace.txt")
+
+        # Content with trailing whitespace
+        content_with_whitespace = "Line 1  \nLine 2 \t \nLine 3\n  Line 4  \n"
+
+        # Expected content after whitespace stripping
+        # Note: The trailing newline is preserved
+        expected_content = "Line 1\nLine 2\nLine 3\n  Line 4"
+
+        async with self.create_client_session() as session:
+            # Initialize project to get chat_id
+            init_result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "InitProject",
+                    "path": self.temp_dir.name,
+                    "user_prompt": "Test initialization for trailing whitespace test",
+                    "subject_line": "test: initialize for trailing whitespace test",
+                    "reuse_head_chat_id": False,
+                },
+            )
+
+            # Extract chat_id from the init result
+            chat_id = self.extract_chat_id_from_text(init_result_text)
+
+            # Call the WriteFile tool with content containing trailing whitespace
+            result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "WriteFile",
+                    "path": test_file_path,
+                    "content": content_with_whitespace,
+                    "description": "Create file with trailing whitespace",
+                    "chat_id": chat_id,
+                },
+            )
+
+            # Verify the success message
+            self.assertIn("Successfully wrote to", result_text)
+
+            # Verify the file was created with trailing whitespace removed
+            with open(test_file_path) as f:
+                file_content = f.read()
+
+            self.assertEqual(file_content, expected_content)
+
+    async def test_edit_file_strips_trailing_whitespace(self):
+        """Test that the EditFile subtool strips trailing whitespace from each line."""
+        # Create a test file with multiple lines
+        test_file_path = os.path.join(self.temp_dir.name, "edit_whitespace.txt")
+        original_content = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5\n"
+        with open(test_file_path, "w") as f:
+            f.write(original_content)
+
+        # Add the file to git and commit it
+        await self.git_run(["add", "edit_whitespace.txt"], check=False)
+        await self.git_run(
+            ["commit", "-m", "Add file for editing with whitespace"], check=False
+        )
+
+        # Edit the file with content containing trailing whitespace
+        old_string = "Line 2\nLine 3\n"
+        new_string_with_whitespace = "Line 2  \nModified Line 3 \t \n"
+
+        async with self.create_client_session() as session:
+            # Initialize project to get chat_id
+            init_result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "InitProject",
+                    "path": self.temp_dir.name,
+                    "user_prompt": "Test initialization for edit file whitespace test",
+                    "subject_line": "test: initialize for edit file whitespace test",
+                    "reuse_head_chat_id": False,
+                },
+            )
+
+            # Extract chat_id from the init result
+            chat_id = self.extract_chat_id_from_text(init_result_text)
+
+            # Call the EditFile tool with content containing trailing whitespace
+            result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "EditFile",
+                    "path": test_file_path,
+                    "old_string": old_string,
+                    "new_string": new_string_with_whitespace,
+                    "description": "Modify content with trailing whitespace",
+                    "chat_id": chat_id,
+                },
+            )
+
+            # Verify the success message
+            self.assertIn("Successfully edited", result_text)
+
+            # Verify the file was edited with trailing whitespace removed
+            with open(test_file_path) as f:
+                file_content = f.read()
+
+            expected_content = "Line 1\nLine 2\nModified Line 3\nLine 4\nLine 5"
+            self.assertEqual(file_content, expected_content)
+
+    async def test_empty_lines_preserved(self):
+        """Test that empty lines are preserved when stripping trailing whitespace."""
+        test_file_path = os.path.join(self.temp_dir.name, "empty_lines.txt")
+
+        # Content with empty lines and whitespace-only lines
+        content_with_empty_lines = "Line 1\n\n \t \nLine 2\n"
+
+        # Expected content after whitespace stripping
+        # The whitespace-only line should become an empty line
+        expected_content = "Line 1\n\n\nLine 2"
+
+        async with self.create_client_session() as session:
+            # Initialize project to get chat_id
+            init_result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "InitProject",
+                    "path": self.temp_dir.name,
+                    "user_prompt": "Test initialization for empty lines test",
+                    "subject_line": "test: initialize for empty lines test",
+                    "reuse_head_chat_id": False,
+                },
+            )
+
+            # Extract chat_id from the init result
+            chat_id = self.extract_chat_id_from_text(init_result_text)
+
+            # Call the WriteFile tool with content containing empty lines
+            result_text = await self.call_tool_assert_success(
+                session,
+                "codemcp",
+                {
+                    "subtool": "WriteFile",
+                    "path": test_file_path,
+                    "content": content_with_empty_lines,
+                    "description": "Create file with empty lines",
+                    "chat_id": chat_id,
+                },
+            )
+
+            # Verify the success message
+            self.assertIn("Successfully wrote to", result_text)
+
+            # Verify the file was created with empty lines preserved
+            with open(test_file_path) as f:
+                file_content = f.read()
+
+            self.assertEqual(file_content, expected_content)
+
+
+class OutOfProcessTrailingWhitespaceTest(TrailingWhitespaceTest):
+    in_process = False
+
+
+if __name__ == "__main__":
+    unittest.main()