tegwick
bd1d05ba79
Add change detection, structural diff-based impact analysis, configurable-depth incremental recomputation with circular suppression, and impact debt tracking. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
96 lines
2.8 KiB
Python
96 lines
2.8 KiB
Python
"""
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Pure diff functions for impact analysis.
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Implements FR-8.2: Structural diff-based impact measurement.
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Uses difflib.SequenceMatcher for computing change magnitude between
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old and new content versions.
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"""
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import difflib
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from typing import Optional
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def structural_diff_ratio(old_content: str, new_content: str) -> float:
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"""
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Calculate structural similarity ratio between old and new content.
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Uses SequenceMatcher to compute a ratio of matching blocks.
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Returns the *change* ratio (1.0 - similarity), so higher values
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mean more change.
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Args:
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old_content: Previous content
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new_content: Current content
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Returns:
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Change ratio from 0.0 (identical) to 1.0 (completely different)
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"""
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if old_content == new_content:
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return 0.0
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if not old_content and not new_content:
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return 0.0
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if not old_content or not new_content:
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return 1.0
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matcher = difflib.SequenceMatcher(None, old_content, new_content)
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similarity = matcher.ratio()
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return 1.0 - similarity
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def line_diff_ratio(old_content: str, new_content: str) -> float:
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"""
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Calculate line-level change ratio between old and new content.
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Splits content into lines and computes SequenceMatcher ratio
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at the line level. Returns the change ratio.
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Args:
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old_content: Previous content
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new_content: Current content
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Returns:
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Change ratio from 0.0 (identical) to 1.0 (completely different)
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"""
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if old_content == new_content:
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return 0.0
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if not old_content and not new_content:
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return 0.0
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if not old_content or not new_content:
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return 1.0
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old_lines = old_content.splitlines()
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new_lines = new_content.splitlines()
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matcher = difflib.SequenceMatcher(None, old_lines, new_lines)
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similarity = matcher.ratio()
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return 1.0 - similarity
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def calculate_change_magnitude(
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old_content: Optional[str],
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new_content: Optional[str],
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method: str = "structural",
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) -> float:
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"""
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Calculate the magnitude of a change between two content versions.
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This is the primary entry point for impact measurement (FR-8.2).
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Args:
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old_content: Previous content (None for created artifacts)
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new_content: Current content (None for deleted artifacts)
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method: Diff method to use ("structural" or "line")
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Returns:
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Change magnitude from 0.0 (no change) to 1.0 (complete change)
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"""
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# Handle None cases (creation/deletion)
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if old_content is None and new_content is None:
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return 0.0
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if old_content is None or new_content is None:
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return 1.0
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if method == "line":
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return line_diff_ratio(old_content, new_content)
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return structural_diff_ratio(old_content, new_content)
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