Block Level Error Detection

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Block Level Error Detection

Level: Master

Description

Implement comprehensive error detection and reporting for indentation-based block structure, focusing on consistency and clarity of error messages.

Technical Details

Changes Needed in parser.py

1. Add indentation validation:

   class IndentationTracker:
   def __init__(self):
       self.indent_stack = [0]
       self.indent_size = 4  # Standard indent size
       self.current_line = 1
       self.tab_seen = False
       self.space_seen = False
   
   def validate_indent(self, indent_str, line_no):
       """Validate indentation string for consistency"""
       if '\t' in indent_str:
           if self.space_seen:
               raise IndentationError(
                   "Mixed tabs and spaces",
                   line_no
               )
           self.tab_seen = True
   
       if ' ' in indent_str:
           if self.tab_seen:
               raise IndentationError(
                   "Mixed tabs and spaces",
                   line_no
               )
           self.space_seen = True

2. Add error context collection:

   class ErrorContext:
   def __init__(self):
       self.source_lines = []
       self.error_line = 0
       self.error_col = 0
       self.error_type = None
   
   def collect_context(self, line_no, window=2):
       """Collect source lines around error"""
       start = max(0, line_no - window)
       end = line_no + window
       return self.source_lines[start:end]

3. Add enhanced error reporting:

   
   def format_error(self, message, line_no, col_no=None):
   context = self.error_context.collect_context(line_no)
   return f"""
   Error at line {line_no}{f", column {col_no}" if col_no else ''}
   {message}

Context: {self._format_context(context, line_no)} """

## Test Cases

### Test Case 1: Mixed Indentation
```python
task "Mixed"
    x = 1
    y = 2  # Tab instead of spaces

Should detect and report mixed indentation.

Test Case 2: Inconsistent Indentation

task "Inconsistent"
    x = 1
      y = 2  # Wrong indentation level

Should detect and report inconsistent level.

Test Case 3: Under-Indentation

task "Under"
    if x > 0
    y = 1  # Missing indentation

Should detect and report missing indentation.

Test Case 4: Over-Indentation

task "Over"
    x = 1
        y = 2  # Extra indentation

Should detect and report extra indentation.

Test Case 5: Complex Nesting

task "Complex"
    if x > 0
        for item in items
          process(item)  # Wrong indent level

Should detect and report inconsistent nesting.

Completion Criteria

1. [ ] Detects mixed tabs and spaces
2. [ ] Detects inconsistent indentation levels
3. [ ] Detects missing required indentation
4. [ ] Detects excessive indentation
5. [ ] Provides clear error messages
6. [ ] Shows relevant source context
7. [ ] Reports correct line numbers
8. [ ] Reports correct column numbers
9. [ ] All test cases pass
10. [ ] Error messages are user-friendly

Dependencies

• Issue #21 : Basic Indentation Tracking
• Issue #22 : Enhanced Newline Handling

Documentation Updates Needed

• Document indentation rules
• Document error message format
• Add troubleshooting guide
• Update style guide
• Add common error examples

Testing Instructions

1. Run provided test cases
2. Verify error messages
3. Check context display
4. Validate line numbers
5. Test complex scenarios
6. Verify user-friendliness

Error Message Format Example

Error at line 3, column 1
Inconsistent indentation: expected 4 spaces, found 2

Context:
  1 | task "Example"
  2 |     x = 1
> 3 |   y = 2
  4 |     z = 3
  5 | 

Expected:
    y = 2
Found:
  y = 2