feat: enable typescript eslint rules requiring type information (#62)

- Added type-aware rules from @typescript-eslint/recommended-type-checked
- Configured ESLint to use TypeScript compiler for enhanced type checking
- Rules catch floating promises, unsafe type assertions, and other subtle issues
- Applied to src/**/*.ts and tests/**/*.ts files only
- Performance impact minimal (~1.5s for full project lint)

Closes #61

Author: sapientpants

.changeset/enable-type-aware-linting.md

@@ -0,0 +1,14 @@
+---
+'agentic-node-ts-starter': minor
+---
+
+feat: Enable TypeScript ESLint rules requiring type information
+
+- Added TypeScript ESLint type-aware rules (@typescript-eslint/recommended-type-checked)
+- Configured ESLint to use TypeScript compiler for enhanced type checking
+- Type-aware rules now catch floating promises, unsafe type assertions, and other subtle type-safety issues
+- Rules apply to src/**/\*.ts and tests/**/\*.ts files
+- Minimal performance impact (~1.5s for full project lint)
+- Improved code quality and runtime safety through compile-time checks
+
+Closes #61

CLAUDE.md

@@ -45,6 +45,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 - **Test-as-contract**: Property-based testing with fast-check for invariants, unit tests with Vitest
 - **Type safety**: Strict TypeScript with runtime validation using Zod for external boundaries
+- **Advanced linting**: TypeScript ESLint with type-aware rules for catching subtle type-safety issues
 - **Module system**: ES modules (`"type": "module"`) with NodeNext resolution
 - **Claude Commands**: Custom commands in `.claude/commands/` for common workflows
 - **Git Hooks**: Custom pre-commit verification via `.claude/hooks/`
@@ -153,7 +154,10 @@ Available slash commands in `.claude/commands/`:
 - **Node Version**: >=22.0.0 (engines requirement)
 - **TypeScript**: Strict mode with NodeNext module resolution
 - **Testing**: Vitest with V8 coverage provider
-- **Linting**: ESLint 9 with TypeScript support
+- **Linting**: ESLint 9 with TypeScript support and type-aware rules enabled
+  - Catches floating promises, unsafe type assertions, and other type-safety issues
+  - Type-aware rules apply to `src/**/*.ts` and `tests/**/*.ts` files
+  - Performance impact: ~1.5s for full project lint (acceptable trade-off for improved safety)
 - **Formatting**: Prettier 3 with ESLint integration
 - **Versioning**: Changesets for automated version management
 

eslint.config.js

@@ -2,14 +2,22 @@
 import tseslint from '@typescript-eslint/eslint-plugin';
 import tsParser from '@typescript-eslint/parser';
 import eslintConfigPrettier from 'eslint-config-prettier';
+import { fileURLToPath } from 'node:url';
+import { dirname } from 'node:path';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
 
 /** @type {import('eslint').Linter.FlatConfig[]} */
 export default [
+  // Base configuration for all JS/TS files
   {
     files: ['**/*.{ts,tsx,js}'],
     languageOptions: {
       parser: tsParser,
-      parserOptions: { ecmaVersion: 2024, sourceType: 'module' },
+      parserOptions: {
+        ecmaVersion: 2024,
+        sourceType: 'module',
+      },
     },
     plugins: { '@typescript-eslint': tseslint },
     rules: {
@@ -18,6 +26,22 @@ export default [
       'no-debugger': 'error',
     },
   },
+  // Type-aware rules for TypeScript files only
+  {
+    files: ['src/**/*.ts', 'tests/**/*.ts'],
+    languageOptions: {
+      parser: tsParser,
+      parserOptions: {
+        ecmaVersion: 2024,
+        sourceType: 'module',
+        project: true,
+        tsconfigRootDir: __dirname,
+      },
+    },
+    rules: {
+      ...tseslint.configs['recommended-type-checked'].rules,
+    },
+  },
   // Keep Prettier last
   eslintConfigPrettier,
 ];