import eslint from "@eslint/js";
import tseslint from "typescript-eslint";
export default tseslint.config(
// Base JS rules
eslint.configs.recommended,
// TypeScript type-checked rules
...tseslint.configs.recommendedTypeChecked,
// Parser options for type-aware linting
{
languageOptions: {
parserOptions: {
project: "./tsconfig.eslint.json",
tsconfigRootDir: import.meta.dirname,
},
},
},
// ── Project rules (informed by bug history analysis) ─────────────
//
// Rule severity guide:
// "error" = blocks commit (real bugs, auto-fixable issues)
// "warn" = informational (improve incrementally, doesn't block)
// "off" = too noisy or false positives
//
{
rules: {
// ── Async/Promise (13% of historical bugs) ───────────────────
// Catches forgotten await, fire-and-forget without void, misused promises
"@typescript-eslint/no-floating-promises": "error",
"@typescript-eslint/no-misused-promises": "error",
"@typescript-eslint/await-thenable": "error",
"@typescript-eslint/promise-function-async": "warn",
// require-await: off — too many false positives for interface conformance
"@typescript-eslint/require-await": "off",
// require-atomic-updates: off — false positives on local variables
"require-atomic-updates": "off",
// ── Type safety (16% of historical bugs) ─────────────────────
"@typescript-eslint/no-unsafe-member-access": "warn",
"@typescript-eslint/no-unsafe-call": "warn",
"@typescript-eslint/no-unsafe-assignment": "warn",
"@typescript-eslint/no-unsafe-argument": "warn",
"@typescript-eslint/no-unsafe-return": "warn",
"@typescript-eslint/no-unnecessary-type-assertion": "error",
"@typescript-eslint/consistent-type-imports": ["error", { prefer: "type-imports" }],
"@typescript-eslint/consistent-type-exports": ["error", { fixMixedExportsWithInlineTypeSpecifier: true }],
"@typescript-eslint/no-import-type-side-effects": "error",
"@typescript-eslint/no-non-null-assertion": "warn",
"@typescript-eslint/prefer-readonly": "warn",
// ── Logic errors (30% of historical bugs) ────────────────────
"@typescript-eslint/switch-exhaustiveness-check": "error",
eqeqeq: ["error", "always"],
"no-constant-condition": "error",
"@typescript-eslint/no-unnecessary-condition": "off", // Too many false positives (49 hits)
"@typescript-eslint/prefer-nullish-coalescing": "off", // 146 hits, many intentional
// ── Unused code ──────────────────────────────────────────────
"@typescript-eslint/no-unused-vars": [
"error",
{
argsIgnorePattern: "^_",
varsIgnorePattern: "^_",
caughtErrorsIgnorePattern: "^_",
},
],
"no-unreachable": "error",
"@typescript-eslint/no-unused-expressions": "error",
// ── Code quality & best practices ────────────────────────────
"@typescript-eslint/no-explicit-any": "warn",
"@typescript-eslint/prefer-string-starts-ends-with": "error",
"@typescript-eslint/prefer-includes": "error",
"@typescript-eslint/prefer-optional-chain": "error",
"@typescript-eslint/prefer-for-of": "warn",
"@typescript-eslint/prefer-as-const": "error",
"@typescript-eslint/no-unnecessary-type-parameters": "warn",
"@typescript-eslint/no-inferrable-types": "error",
"@typescript-eslint/array-type": ["error", { default: "array" }],
"@typescript-eslint/method-signature-style": ["error", "property"],
"@typescript-eslint/unbound-method": "warn",
"no-console": "off", // MCP server — console.error is the log channel
// ── Error handling ───────────────────────────────────────────
"@typescript-eslint/only-throw-error": "warn",
"@typescript-eslint/prefer-promise-reject-errors": "warn",
"no-throw-literal": "off", // Superseded by @typescript-eslint/only-throw-error
// ── Return types & signatures ────────────────────────────────
"@typescript-eslint/explicit-function-return-type": "off", // TypeScript infers well enough
"@typescript-eslint/explicit-module-boundary-types": "off", // Same reason
"@typescript-eslint/no-confusing-void-expression": "warn",
// ── Inherited from recommendedTypeChecked (calibrated) ───────
"@typescript-eslint/restrict-template-expressions": "warn",
"@typescript-eslint/no-redundant-type-constituents": "warn",
// ── ESLint core best practices ───────────────────────────────
"no-eval": "error",
"no-implied-eval": "off", // Superseded by @typescript-eslint/no-implied-eval
"@typescript-eslint/no-implied-eval": "error",
"no-new-func": "error",
"no-param-reassign": "warn",
"no-return-assign": "error",
"no-self-compare": "error",
"no-sequences": "error",
"no-template-curly-in-string": "warn",
"no-unmodified-loop-condition": "error",
"no-useless-concat": "error",
"prefer-template": "warn",
"no-else-return": "warn",
"no-lonely-if": "warn",
"no-useless-return": "error",
"object-shorthand": ["warn", "always"],
"prefer-const": "error",
"prefer-destructuring": ["warn", { object: true, array: false }],
"prefer-rest-params": "error",
"prefer-spread": "error",
"symbol-description": "error",
curly: ["error", "multi-line"],
},
},
// ── Test files: relax strict rules ───────────────────────────────
{
files: ["**/*.test.ts", "tests/**/*.ts", "tests/**/*.mjs"],
rules: {
"@typescript-eslint/no-unsafe-member-access": "off",
"@typescript-eslint/no-unsafe-call": "off",
"@typescript-eslint/no-unsafe-assignment": "off",
"@typescript-eslint/no-unsafe-argument": "off",
"@typescript-eslint/no-unsafe-return": "off",
"@typescript-eslint/no-explicit-any": "off",
"@typescript-eslint/no-floating-promises": "error", // Keep — catches real bugs in tests too
"@typescript-eslint/no-non-null-assertion": "off", // Common in tests for assertions
"@typescript-eslint/unbound-method": "off",
"no-param-reassign": "off", // Acceptable in test setup
"@typescript-eslint/prefer-readonly": "off",
},
},
// ── Benchmark/script files: minimal rules ────────────────────────
{
files: ["benchmarks/**/*.mjs", "scripts/**/*.js"],
...tseslint.configs.disableTypeChecked,
},
// ── Ignore patterns ──────────────────────────────────────────────
{
ignores: [
"build/",
"coverage/",
"node_modules/",
"*.d.ts",
"eslint.config.js", // Root JS config — not in tsconfig
"tests/code/fixtures/",
"tests/integration/", // Plain .mjs — run separately via npm run test-integration
"website/", // Docusaurus — own tsconfig, own build pipeline
],
},
);
