# Phase 6-3: G004 Logging F-String Error Resolution

**Status**: Complete (339/339 errors fixed = 100%)

## Summary

G004 is a Ruff linting rule that requires logging statements to use lazy evaluation (% formatting) rather than f-strings for performance and PEP 391 compliance.

### Pattern
`python
# ❌ Before (G004 violation)
logger.info(f"Processing {item_id}: {status}")

# ✅ After (G004 compliant)
logger.info("Processing %s: %s", item_id, status)
`

## Results

- Total violations prior to remediation: 339 across 85 files
- Remaining violations after remediation: **0**
- Automated conversion coverage: 331 occurrences via scripts/convert_logging_fstrings.py
- Manual conversions: 8 multi-line cases in src/noveler/application/simple_message_bus.py

## Implementation Notes

1. Added scripts/convert_logging_fstrings.py to analyse the working tree and rewrite logging calls with lazy % formatting.
2. Added Makefile target make ensure-g004 (invoked by make lint / CI) to auto-run the converter and fail the build if changes are required.
3. Automated replacements format logging calls as multi-line blocks for readability and consistency.
4. Validated conversions with python -m ruff check src --select G004 → **All checks passed**.
5. Confirmed syntax integrity via python -m compileall src.

### Example
`python
self.logger.info(
    "MessageBus Metrics: cmd_count=%s, cmd_p95=%.1fms, cmd_fail_rate=%.2f%%, "
    "event_count=%s, event_p95=%.1fms, event_fail_rate=%.2f%%",
    cmd_stats["count"],
    cmd_stats["p95_ms"],
    cmd_stats["failure_rate"] * 100,
    event_stats["count"],
    event_stats["p95_ms"],
    event_stats["failure_rate"] * 100,
)
`

## Follow-Up

- Periodically run make ensure-g004 (or rely on CI’s lint job) to guard against new logging f-string regressions.
- Keep python -m ruff check src --select G004 in local pre-commit routines for immediate feedback.

**Last Updated**: 2025-10-24
**Session**: Phase 6-3 Completion
