Summary

This PR fixes issue #4852 where the apply_diff tool would hang indefinitely when modifying XML files, particularly during the approval phase after Roo has decided on the change but before the file is written.

Root Cause Analysis

The hang was caused by several factors:

1. XML Parsing Timeouts: The multi-file apply diff tool uses parseXml() to parse XML arguments, which could hang indefinitely on complex XML content
2. HTML Entity Double-Processing: XML content was being double-escaped/unescaped when passed through the tool call XML structure
3. Regex Performance Issues: Complex regex patterns in diff strategies could enter infinite loops when processing large XML content with many special characters
4. Lack of XML-Specific Error Handling: No proper timeout mechanisms or XML-specific error handling

Changes Made

1. Safe XML Parsing with Timeout Protection

• Added safeParseXml() function with configurable timeout (default 5 seconds)
• Implemented isProblematicXmlContent() to detect potentially problematic XML patterns
• Enhanced error messages with specific guidance for XML file modifications

2. Improved HTML Entity Handling

• Added safer HTML entity unescaping for XML content
• Detects XML structure and handles entities more conservatively
• Prevents double-unescaping that could corrupt XML content

3. Regex Timeout Protection

• Added timeout mechanisms to regex operations in both diff strategies
• Prevents infinite loops on complex XML content
• Provides helpful error messages when timeouts occur

4. Enhanced Error Messages

• Added specific guidance for XML file modifications
• Suggests breaking down large XML changes into smaller diffs
• Recommends using write_to_file for extensive changes

Files Modified

• src/core/tools/multiApplyDiffTool.ts - Added safe XML parsing and timeout protection
• src/core/tools/applyDiffTool.ts - Improved HTML entity handling for XML content
• src/core/diff/strategies/multi-file-search-replace.ts - Added regex timeout protection
• src/core/diff/strategies/multi-search-replace.ts - Added regex timeout protection

Testing

• All existing tests pass
• Linting and type checking pass
• The fix addresses the specific hang scenario described in the issue

Impact

This fix ensures that:

• XML file modifications no longer hang the apply_diff tool
• Users get helpful error messages when operations timeout
• The tool gracefully handles complex XML content
• Performance is maintained for non-XML files

Closes #4852