#!/usr/bin/env python3
"""
Coverage comparison script for CI.
Compares current coverage with base branch to detect coverage regressions.
"""
import json
import sys
from pathlib import Path
def load_coverage(coverage_file: Path) -> dict | None:
"""Load coverage data from JSON file."""
try:
with coverage_file.open() as f:
return json.load(f)
except (FileNotFoundError, json.JSONDecodeError):
return None
def get_coverage_summary(coverage_data: dict) -> tuple[float, dict[str, float]]:
"""Extract coverage summary from coverage data."""
total_coverage = coverage_data["totals"]["percent_covered"]
file_coverage = {}
for filename, file_data in coverage_data.get("files", {}).items():
if "summary" in file_data:
file_coverage[filename] = file_data["summary"]["percent_covered"]
return total_coverage, file_coverage
def compare_coverage(current_file: Path, base_file: Path | None = None) -> dict[str, any]:
"""Compare current coverage with base coverage."""
current_data = load_coverage(current_file)
if not current_data:
return {"error": f"Could not load current coverage from {current_file}"}
current_total, current_files = get_coverage_summary(current_data)
result = {
"current_coverage": current_total,
"base_coverage": None,
"diff": 0,
"status": "new",
"file_changes": [],
"summary": f"Coverage: {current_total:.1f}%",
}
if base_file and base_file.exists():
base_data = load_coverage(base_file)
if base_data:
base_total, base_files = get_coverage_summary(base_data)
result["base_coverage"] = base_total
result["diff"] = current_total - base_total
result["status"] = (
"improved" if result["diff"] > 0 else "decreased" if result["diff"] < 0 else "same"
)
# Check file-level changes
for filename in set(current_files.keys()) | set(base_files.keys()):
current_cov = current_files.get(filename, 0)
base_cov = base_files.get(filename, 0)
diff = current_cov - base_cov
if abs(diff) > 1: # Only report significant changes
result["file_changes"].append(
{"file": filename, "current": current_cov, "base": base_cov, "diff": diff}
)
# Update summary
if result["diff"] > 0:
result["summary"] = f"Coverage: {current_total:.1f}% (+{result['diff']:.1f}%) ⬆️"
elif result["diff"] < 0:
result["summary"] = f"Coverage: {current_total:.1f}% ({result['diff']:.1f}%) ⬇️"
else:
result["summary"] = f"Coverage: {current_total:.1f}% (no change)"
return result
def generate_coverage_comment(comparison: dict) -> str:
"""Generate markdown comment for coverage comparison."""
lines = []
# Header
lines.append("## 📊 Coverage Report")
lines.append("")
# Summary
status_emoji = {"improved": "✅", "decreased": "⚠️", "same": "➡️", "new": "🆕"}
emoji = status_emoji.get(comparison["status"], "📊")
lines.append(f"{emoji} **{comparison['summary']}**")
lines.append("")
if comparison["base_coverage"] is not None:
# Detailed comparison
lines.append("| Metric | Current | Base | Change |")
lines.append("|--------|---------|------|--------|")
lines.append(
f"| Total Coverage | {comparison['current_coverage']:.1f}% | {comparison['base_coverage']:.1f}% | {comparison['diff']:+.1f}% |"
)
lines.append("")
# File-level changes
if comparison["file_changes"]:
lines.append("### File-level Changes")
lines.append("")
lines.append("| File | Current | Base | Change |")
lines.append("|------|---------|------|--------|")
for change in comparison["file_changes"][:10]: # Limit to 10 files
lines.append(
f"| {change['file']} | {change['current']:.1f}% | {change['base']:.1f}% | {change['diff']:+.1f}% |"
)
if len(comparison["file_changes"]) > 10:
lines.append(f"*... and {len(comparison['file_changes']) - 10} more files*")
lines.append("")
# Threshold check
if comparison["current_coverage"] < 80:
lines.append("⚠️ **Coverage is below 80% threshold**")
lines.append("")
return "\n".join(lines)
def main():
"""Main entry point."""
if len(sys.argv) < 2:
print("Usage: coverage-diff.py <current_coverage.json> [base_coverage.json]")
sys.exit(1)
current_file = Path(sys.argv[1])
base_file = Path(sys.argv[2]) if len(sys.argv) > 2 else None
comparison = compare_coverage(current_file, base_file)
if "error" in comparison:
print(f"Error: {comparison['error']}")
sys.exit(1)
# Print summary for CI logs
print(comparison["summary"])
# Always output markdown for PR comments before exiting
comment = generate_coverage_comment(comparison)
with Path("coverage-comment.md").open("w") as f:
f.write(comment)
print("📝 Coverage comment written to coverage-comment.md")
if comparison["diff"] < -5: # Significant decrease
print(f"⚠️ Coverage decreased by {abs(comparison['diff']):.1f}%")
sys.exit(1)
if __name__ == "__main__":
main()
