fix: log _load_last_report_cache failure to stderr instead of silent swallow (#787)

[23241a6749]

Summary

_load_last_report_cache() caught all Exception and silently returned None (cache miss) with zero diagnostic output. If the cache file at ~/.config/last30days/last-report.json is corrupted, truncated, or version-mismatched, users had no way to know why the cache was being regenerated on every run — wasted token spend and lost performance.

Change

last30days.py:762-763 — replaced except Exception: return None with:

except Exception as exc:
    sys.stderr.write(f"[last30days] Cache read failed, regenerating: {exc}\n")
    return None
``"

The function still returns `None` (cache miss → regenerate), but now emits a diagnostic so users can identify and fix the root cause.

Fixes #787.

[greptile-apps]

Greptile Summary

This PR converts a silent exception swallow in _load_last_report_cache() into a visible stderr diagnostic, helping users identify why the cache is being regenerated on every run. The behavioral contract is unchanged — the function still returns None on any error, triggering a cache miss and regeneration.

• last30days.py: Binds the caught exception to exc and emits [last30days] Cache read failed, regenerating: {exc} to stderr before returning None. Uses the same sys.stderr.write() pattern already established in the file (e.g., the Python version check at line 28).
• uv.lock: Reflects the 3.11.0 → 3.11.1 patch version bump already present in pyproject.toml.

Confidence Score: 5/5

Safe to merge — a two-line addition that adds observability without changing any functional behavior.

The change is minimal and targeted: it binds the caught exception and writes a single diagnostic line to stderr before the existing return None. sys is already imported and sys.stderr.write() is used elsewhere in the file for the same purpose. No new code paths, no state changes, no risk of regression.

No files require special attention.

Important Files Changed

Filename	Overview
skills/last30days/scripts/last30days.py	Two-line change: binds caught exception as exc and writes a diagnostic to stderr before returning None; no behavioral change, follows existing sys.stderr.write() pattern in the file.
uv.lock	Auto-generated lock file update reflecting the 3.11.0 → 3.11.1 version bump in pyproject.toml.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[_load_last_report_cache called] --> B[Open & parse cache JSON]
    B --> C{Parse OK?}
    C -- yes --> D[Validate payload / entity_reports]
    D --> E{Valid?}
    E -- yes --> F[Return cached report tuple]
    E -- no --> G[Return None\ncache miss]
    C -- no --> H["BEFORE: silent except Exception: return None"]
    C -- no --> I["AFTER: sys.stderr.write diagnostic + return None"]
    H --> J[Caller regenerates report\nno feedback to user]
    I --> K["stderr: [last30days] Cache read failed, regenerating: exc"]
    K --> L[Caller regenerates report\nuser sees root cause]
    style H fill:#fcc,stroke:#c00
    style I fill:#cfc,stroke:#090
    style K fill:#cfc,stroke:#090

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flowchart TD
    A[_load_last_report_cache called] --> B[Open & parse cache JSON]
    B --> C{Parse OK?}
    C -- yes --> D[Validate payload / entity_reports]
    D --> E{Valid?}
    E -- yes --> F[Return cached report tuple]
    E -- no --> G[Return None\ncache miss]
    C -- no --> H["BEFORE: silent except Exception: return None"]
    C -- no --> I["AFTER: sys.stderr.write diagnostic + return None"]
    H --> J[Caller regenerates report\nno feedback to user]
    I --> K["stderr: [last30days] Cache read failed, regenerating: exc"]
    K --> L[Caller regenerates report\nuser sees root cause]
    style H fill:#fcc,stroke:#c00
    style I fill:#cfc,stroke:#090
    style K fill:#cfc,stroke:#090

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_{Reviews (2): Last reviewed commit: "chore: update uv.lock for v3.11.1" | Re-trigger Greptile}