ADR-0005: Strict TypeScript with projectService

Status: Accepted Date: 2026-03-02

Context

TypeScript-ESLint offers multiple preset tiers: recommended, strict, and strictTypeChecked. Type-checked rules (requiring a tsconfig.json) catch significantly more bugs (e.g. no-floating-promises, no-misused-promises, restrict-template-expressions) but require parser configuration pointing to a TypeScript project.

Decision

Use tseslint.configs.strictTypeChecked and tseslint.configs.stylisticTypeChecked as the baseline. Enable parserOptions.projectService: true for automatic tsconfig discovery — no manual project paths needed.

Plain JavaScript files (*.js, *.mjs, *.cjs) automatically get type-checked rules disabled via tseslint.configs.disableTypeChecked.

Consequences

Maximum type safety out of the box — strictest available preset
projectService: true eliminates tsconfig path management for consumers
Requires typescript as a peer dependency
Type-checked rules only work in projects with a tsconfig.json
Preset rules are further customized (e.g. no-unused-vars with underscore pattern, array-type with array-simple)