[Bug/Improvement] Backend Crashes, Missing Validation, Logging & Test Count Fixes

[Ketan444]

@imDarshanGK

🐛 Bug Report & Code Quality Improvements

Summary

After reviewing the repository, here are several bugs, debugging issues, and improvements identified across the backend, frontend, and documentation.

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🔴 Bugs

1. README / project tree references auth.py router that may not exist

• File path: backend/app/routers/auth.py
• If imported in main.py but missing, the app will crash on startup with ImportError
• Fix: Either add the file or remove the reference from the README and main.py

2. No cold-start handling in frontend for Render free tier

• First request after inactivity takes 30–60 seconds but the frontend shows no loading state
• Users see a silent timeout/failure with no feedback
• Fix: Add a "Server is waking up, please wait..." indicator with a 60s timeout

3. Language auto-detection has no documented failure behavior

• When language is omitted and detection fails, there is no defined fallback response
• Fix: Return a clear error or default to "unknown" with a warning in the response

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🟡 Debugging / Code Quality

4. No input length validation on code field

• Very large payloads can exhaust memory during pattern matching
• Fix: Add a Pydantic validator e.g. max_length=50000 on the code field in schemas.py

5. Rate limiting breaks behind Render's reverse proxy

• Per-IP rate limiting may treat all users as one IP behind a shared proxy
• Fix: Use X-Forwarded-For header or switch to a token/session-based limiter

6. Test count in README is wrong (says 22, actually 52)

• Misleads contributors about test coverage
• Fix: Update README to reflect the real test count

7. No structured logging

• Errors in production are invisible without logging or loguru
• Fix: Add a basic logging setup in main.py with request/response logging middleware

8. CI Python versions may not match Dockerfile

• CI tests 3.11 + 3.12 but Dockerfile base image version is unverified
• Fix: Pin the same Python version in both ci.yml and Dockerfile

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🟢 Improvements

9. No frontend paste size limit

• Users can paste unlimited code; add a client-side size check before sending

10. Quality score breakdown not exposed

• The 0–100 score is opaque; expose sub-scores (documentation, error handling, types, tests) in the API response

11. Add CHANGELOG.md

• With 248+ commits and active GSSoC contributors, a changelog helps track progress

12. LLM code paths have zero test coverage in CI

• Add mock-based tests for ai_provider.py so LLM integration doesn't silently break

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Environment

• Backend: FastAPI 0.115+, Python 3.12
• Frontend: Vanilla JS / HTML5
• Deployment: Render (free tier)

Labels suggested

bug, documentation, good first issue, enhancement

[kalyani-jadhav-project]

Hi @maintainer, I would like to work on this issue under GSSoC.

I would like to start with Bug #4: Adding input length validation on the code field using Pydantic.

Please assign this to me.