finlint-check

Zero-config financial code scanner. Find float precision bugs instantly — no ESLint config, no pylint, no YAML.

npx finlint-check .

What it finds

16 rules across JavaScript/TypeScript (AST-based) and Python (regex-based):

JS/TS (8 rules)

| Rule | Severity | Detects | |------|----------|---------| | no-float-money | CRITICAL | const amount = 19.99, price: number | | money-parse | HIGH | parseFloat(amount), Number(price), +amount | | no-math-round-money | HIGH | Math.round(amount) | | decimal-from-string | HIGH | new Decimal(0.1) | | intl-number-format | MEDIUM | amount.toFixed(2) | | no-json-number-parse | MEDIUM | JSON.parse(data) without reviver | | negative-zero-check | MEDIUM | amount === 0 | | intl-format-only | MEDIUM | "$" + amount |

Python (8 rules)

| Rule | Severity | Detects | |------|----------|---------| | FIN001 | CRITICAL | amount = 19.99, balance: float | | FIN002 | HIGH | Decimal(0.1) | | FIN004 | HIGH | round(amount, 2) | | FIN010 | HIGH | amount * 0.15 | | FIN005 | MEDIUM | class Invoice(BaseModel): amount: float | | FIN006 | MEDIUM | {"amount": 19.99} | | FIN007 | MEDIUM | Column(Float) | | PIPE005 | MEDIUM | Decimal("10") * 0.5 |

Output

finlint-check v1.0.0 — scanned 47 files

  CRITICAL  src/billing.js:23    float literal on financial variable 'amount' (no-float-money)
  HIGH      src/cart.ts:89       parseFloat() on financial variable 'price' (money-parse)
  MEDIUM    src/tax.js:12        .toFixed() on financial variable 'tax' (intl-number-format)

Found 3 issues in 47 files (1 critical, 1 high, 1 medium)

Fix guide: https://finlint.dev/fix

Options

--format <text|json|github-actions>  Output format (default: text)
--js-only                            Scan only JS/TS files
--py-only                            Scan only Python files
--ignore <pattern>                   Exclude files matching glob (repeatable)
--quiet, -q                          Suppress warnings (only output issues)
--version                            Print version
--help                               Show help

CI Integration

# GitHub Actions
- run: npx finlint-check . --format github-actions

Exit Codes

• 0 — No issues found
• 1 — Issues found
• 2 — Usage error

File Discovery

Automatically excludes: node_modules/, .git/, __pycache__/, .venv/, dist/, build/, *.min.js, files >1MB. Respects .gitignore.

License

Apache-2.0