Developer Experience Baseline for Solo Polyglot Development

Executive Summary

For a solo developer working primarily with Python, JavaScript/TypeScript, and Rust, Ruff + Pyright + Biome.js provides the optimal balance of performance, simplicity, and comprehensive coverage. This baseline enables a "gentle introduction" approach with permissive initial settings that progressively tighten as habits form.

Tool Selection Matrix

Python Development Stack

Linting/Formatting: Ruff (unanimous winner)

• 10-100x faster than Black+isort+flake8 combined
• Single tool replaces 6+ traditional tools
• Drop-in Black compatibility (>99.9%)
• Zero configuration with sensible defaults

Type Checking: Pyright (for solo developers)

• 3-5x faster than mypy on large codebases
• Superior type inference without annotations
• Native VS Code integration via Pylance
• Switch to mypy only if heavy Pydantic usage requires plugin features

Testing/Coverage: pytest + coverage.py

• coverage.py directly (skip pytest-cov wrapper)
• mutmut for mutation testing on critical modules only
• Target: 60% → 70% → 80% coverage progression

Security: pip-audit + Semgrep + Gitleaks

• pip-audit replaces Safety (licensing changes)
• Semgrep over Bandit for multi-language support
• Gitleaks for secrets scanning (2-5 seconds overhead)

JavaScript/TypeScript Stack

All-in-One: Biome.js

• 80% faster than ESLint + Prettier
• Single configuration file
• Excellent VS Code integration

Rust Integration

Standard tooling with Python-friendly configs:

• rustfmt with 88-character line width (matching Black)
• cargo-watch, cargo-outdated for familiar workflows
• Maturin for Python-Rust bridges

Progressive Configuration Examples

Stage 1: Minimal Baseline (Week 1)

# pyproject.toml
[tool.ruff]
select = ["F", "E4", "E7", "E9"]  # Critical errors only
line-length = 88
fix = true

# pyrightconfig.json
{
    "typeCheckingMode": "basic",
    "reportMissingImports": "warning"
}

# .pre-commit-config.yaml
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer
      - id: check-yaml
  
  - repo: https://github.com/astral-sh/ruff-pre-commit
    rev: v0.1.8
    hooks:
      - id: ruff
        args: [--fix]
      - id: ruff-format

Time impact: 5-10 seconds per commit

Stage 2: Enhanced Quality (Week 3)

# pyproject.toml additions
[tool.ruff]
select = ["F", "E", "W", "B", "I"]  # Expand rule coverage
ignore = ["E501"]  # Still allow long lines initially

[tool.coverage.run]
source = ["."]
omit = ["*/tests/*", "*/venv/*"]
branch = true

[tool.coverage.report]
fail_under = 70  # Enforce minimum coverage

Add to pre-commit:

  - repo: https://github.com/gitleaks/gitleaks
    rev: v8.22.1
    hooks:
      - id: gitleaks

Stage 3: Production Ready (Week 5+)

[tool.ruff]
select = ["ALL"]
ignore = ["D", "ANN", "TD", "FIX"]  # Skip docs/annotations initially
line-length = 88

[tool.ruff.mccabe]
max-complexity = 10

# biome.json for JS/TS
{
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "complexity": {
        "noExcessiveCognitiveComplexity": "error"
      }
    }
  }
}

Phased Adoption Plan

Week 1-2: Foundation (4 hours setup)

1. Install Ruff, configure with minimal rules
2. Set up basic pre-commit hooks
3. Create pyrightconfig.json with "basic" mode
4. Target 60% test coverage

Week 3-4: Enhancement (2 hours/week)

1. Add Gitleaks to pre-commit
2. Configure pip-audit for weekly runs
3. Expand Ruff rules gradually
4. Increase coverage target to 70%

Week 5-6: Optimization (1 hour/week)

1. Add Biome.js for JS/TS projects
2. Configure Semgrep with basic Python rules
3. Set up mutation testing for core modules
4. Target 80% coverage

Month 2+: Maturity

1. Enable stricter Ruff rules (complexity, naming)
2. Add Vulture for dead code detection
3. Implement full polyglot pre-commit suite
4. Automate dependency updates

Maintenance Automation

#!/bin/bash
# weekly-maintenance.sh
pip-audit --fix
pip-review --auto
pre-commit autoupdate
ruff check . --fix
coverage report --fail-under=80

Documentation Standards

Use this minimal structure:

project/
├── README.md          # Quick start, badges, structure
├── CONTRIBUTING.md    # Dev setup, style guide
├── .github/
│   └── ISSUE_TEMPLATE/
└── docs/
    └── decisions/     # Architecture Decision Records

Risk Mitigation

Tool Lock-in: Pin tool versions in requirements-dev.txt

ruff==0.1.8
pyright==1.1.339
biome==1.5.0

False Positives: Start with permissive configs, use inline suppressions:

# ruff: noqa: F401  # Temporary import for side effects

Performance Degradation: Monitor pre-commit times:

# Skip expensive hooks when needed
SKIP=mypy,pytest git commit -m "hotfix"

Migration Fatigue: Adopt one tool at a time, allow 2 weeks per tool for habit formation.