Linting & Formatting Strategy

Overview

Toast uses Biome for linting and import organization. Formatting is handled separately by Prettier (Biome formatter is disabled).

Rule	Why
`noUnusedImports`	Dead code
`noUnusedVariables`	Dead code
`noUndeclaredDependencies`	Missing package.json entries
`noExplicitAny`	Type safety — use `unknown` instead
`noNonNullAssertion`	Type safety — handle null explicitly
`noDoubleEquals`	Use `===` always
`noAssignInExpressions`	Prevents accidental `=` vs `===`
`noAsyncPromiseExecutor`	Error handling correctness
`noParameterAssign`	Prevents confusing mutation
`useConst`	Prefer `const` over `let`
`useImportType` / `useExportType`	Correct type-only imports/exports
`noConfusingVoidType`	Prevents misuse of `void` in unions
`noMisleadingInstantiator`	Constructor/`new()` return-type bugs
`noConsole` (API server only)	Use structured logger instead

Rule	Why
`noConsole` (admin/client)	Migrate to structured logging over time
`noEmptyBlockStatements`	Usually incomplete code
`useAwait`	Async functions should use await
`noForEach`	Prefer `for...of` for readability
`useDefaultSwitchClause`	Exhaustive switch handling

Test files (*.test.ts, *.spec.ts): noConsole and useAwait relaxed
Scripts (scripts/): noConsole allowed (CLI output)
API config/logger/error-handler: noConsole allowed (bootstrap + logger internals)
UI component library (packages/ui): linting disabled (third-party adapted code)

These patterns were repeatedly flagged by CodeRabbit and Greptile across PRs #512–#525:

console.error instead of structured logger → noConsole: error on API server
process.env direct access outside config → architectural convention (Biome can't enforce module boundaries, but noConsole on API catches the symptom)
Missing input validation → noDoubleEquals, noAssignInExpressions catch common variants
Parameter reassignment → noParameterAssign catches if (!x) x = default patterns
Unused imports accumulating → noUnusedImports already enforced, now paired with noUndeclaredDependencies

Biome runs as part of pnpm check in CI. Any error-level violation fails the pipeline. Warnings appear in logs but don't block merge.

Install the Biome VS Code extension for real-time feedback. Warnings show as squiggly underlines — fix them as you go.