feat(configs/oxlint): add linter

configs/oxlint/src/compose.ts

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+import type { OxlintConfig } from './types';
+
+/**
+ * Deep merge two objects. Arrays are concatenated, objects are recursively merged.
+ */
+function deepMerge(target: Record<string, unknown>, source: Record<string, unknown>): Record<string, unknown> {
+  const result = { ...target };
+
+  for (const key of Object.keys(source)) {
+    const targetValue = target[key];
+    const sourceValue = source[key];
+
+    if (
+      typeof targetValue === 'object' && targetValue !== null && !Array.isArray(targetValue)
+      && typeof sourceValue === 'object' && sourceValue !== null && !Array.isArray(sourceValue)
+    ) {
+      result[key] = deepMerge(
+        targetValue as Record<string, unknown>,
+        sourceValue as Record<string, unknown>,
+      );
+    }
+    else {
+      result[key] = sourceValue;
+    }
+  }
+
+  return result;
+}
+
+/**
+ * Compose multiple oxlint configurations into a single config.
+ *
+ * - `plugins` — union (deduplicated)
+ * - `categories` — later configs override earlier
+ * - `rules` — later configs override earlier
+ * - `overrides` — concatenated
+ * - `env` — merged (later overrides earlier)
+ * - `globals` — merged (later overrides earlier)
+ * - `settings` — deep-merged
+ * - `ignorePatterns` — concatenated
+ *
+ * @example
+ * ```ts
+ * import { compose, base, typescript, vue } from '@robonen/oxlint';
+ * import { defineConfig } from 'oxlint';
+ *
+ * export default defineConfig(
+ *   compose(base, typescript, vue, {
+ *     rules: { 'eslint/no-console': 'off' },
+ *   }),
+ * );
+ * ```
+ */
+export function compose(...configs: OxlintConfig[]): OxlintConfig {
+  const result: OxlintConfig = {};
+
+  for (const config of configs) {
+    // Plugins — union with dedup
+    if (config.plugins?.length) {
+      result.plugins = Array.from(new Set([...(result.plugins ?? []), ...config.plugins]));
+    }
+
+    // Categories — shallow merge
+    if (config.categories) {
+      result.categories = { ...result.categories, ...config.categories };
+    }
+
+    // Rules — shallow merge (later overrides earlier)
+    if (config.rules) {
+      result.rules = { ...result.rules, ...config.rules };
+    }
+
+    // Overrides — concatenate
+    if (config.overrides?.length) {
+      result.overrides = [...(result.overrides ?? []), ...config.overrides];
+    }
+
+    // Env — shallow merge
+    if (config.env) {
+      result.env = { ...result.env, ...config.env };
+    }
+
+    // Globals — shallow merge
+    if (config.globals) {
+      result.globals = { ...result.globals, ...config.globals };
+    }
+
+    // Settings — deep merge
+    if (config.settings) {
+      result.settings = deepMerge(
+        (result.settings ?? {}) as Record<string, unknown>,
+        config.settings as Record<string, unknown>,
+      );
+    }
+
+    // Ignore patterns — concatenate
+    if (config.ignorePatterns?.length) {
+      result.ignorePatterns = [...(result.ignorePatterns ?? []), ...config.ignorePatterns];
+    }
+  }
+
+  return result;
+}

configs/oxlint/src/index.ts

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+/* Compose */
+export { compose } from './compose';
+
+/* Presets */
+export { base, typescript, vue, vitest, imports, node } from './presets';
+
+/* Types */
+export type {
+  OxlintConfig,
+  OxlintOverride,
+  OxlintEnv,
+  OxlintGlobals,
+  AllowWarnDeny,
+  DummyRule,
+  DummyRuleMap,
+  RuleCategories,
+} from './types';

configs/oxlint/src/presets/base.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * Base configuration for any JavaScript/TypeScript project.
+ *
+ * Enables `correctness` category and opinionated rules from
+ * `eslint`, `oxc`, and `unicorn` plugins.
+ */
+export const base: OxlintConfig = {
+  plugins: ['eslint', 'oxc', 'unicorn'],
+
+  categories: {
+    correctness: 'error',
+  },
+
+  rules: {
+    /* ── eslint core ──────────────────────────────────────── */
+    'eslint/eqeqeq': 'error',
+    'eslint/no-console': 'warn',
+    'eslint/no-debugger': 'error',
+    'eslint/no-eval': 'error',
+    'eslint/no-var': 'error',
+    'eslint/prefer-const': 'error',
+    'eslint/prefer-template': 'warn',
+    'eslint/no-useless-constructor': 'warn',
+    'eslint/no-useless-rename': 'warn',
+    'eslint/no-unused-vars': ['error', { argsIgnorePattern: '^_', varsIgnorePattern: '^_' }],
+    'eslint/no-self-compare': 'error',
+    'eslint/no-template-curly-in-string': 'warn',
+    'eslint/no-throw-literal': 'error',
+    'eslint/no-return-assign': 'warn',
+    'eslint/no-else-return': 'warn',
+    'eslint/no-lonely-if': 'warn',
+    'eslint/no-unneeded-ternary': 'warn',
+    'eslint/prefer-object-spread': 'warn',
+    'eslint/prefer-exponentiation-operator': 'warn',
+    'eslint/no-useless-computed-key': 'warn',
+    'eslint/no-useless-concat': 'warn',
+    'eslint/curly': 'off',
+
+    /* ── unicorn ──────────────────────────────────────────── */
+    'unicorn/prefer-node-protocol': 'error',
+    'unicorn/no-instanceof-array': 'error',
+    'unicorn/no-new-array': 'error',
+    'unicorn/prefer-array-flat-map': 'warn',
+    'unicorn/prefer-array-flat': 'warn',
+    'unicorn/prefer-includes': 'warn',
+    'unicorn/prefer-string-slice': 'warn',
+    'unicorn/prefer-string-starts-ends-with': 'warn',
+    'unicorn/throw-new-error': 'error',
+    'unicorn/error-message': 'warn',
+    'unicorn/no-useless-spread': 'warn',
+    'unicorn/no-useless-undefined': 'off',
+    'unicorn/prefer-optional-catch-binding': 'warn',
+    'unicorn/prefer-type-error': 'warn',
+    'unicorn/no-thenable': 'error',
+    'unicorn/prefer-number-properties': 'warn',
+    'unicorn/prefer-global-this': 'warn',
+
+    /* ── oxc ──────────────────────────────────────────────── */
+    'oxc/no-accumulating-spread': 'warn',
+    'oxc/bad-comparison-sequence': 'error',
+    'oxc/bad-min-max-func': 'error',
+    'oxc/bad-object-literal-comparison': 'error',
+    'oxc/const-comparisons': 'error',
+    'oxc/double-comparisons': 'error',
+    'oxc/erasing-op': 'error',
+    'oxc/missing-throw': 'error',
+    'oxc/bad-bitwise-operator': 'error',
+    'oxc/bad-char-at-comparison': 'error',
+    'oxc/bad-replace-all-arg': 'error',
+  },
+};

configs/oxlint/src/presets/imports.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * Import plugin rules for clean module boundaries.
+ */
+export const imports: OxlintConfig = {
+  plugins: ['import'],
+
+  rules: {
+    'import/no-duplicates': 'error',
+    'import/no-self-import': 'error',
+    'import/no-cycle': 'warn',
+    'import/first': 'warn',
+    'import/no-mutable-exports': 'error',
+    'import/no-amd': 'error',
+    'import/no-commonjs': 'warn',
+    'import/no-empty-named-blocks': 'warn',
+    'import/consistent-type-specifier-style': ['warn', 'prefer-top-level'],
+  },
+};

configs/oxlint/src/presets/index.ts

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+export { base } from './base';
+export { typescript } from './typescript';
+export { vue } from './vue';
+export { vitest } from './vitest';
+export { imports } from './imports';
+export { node } from './node';

configs/oxlint/src/presets/node.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * Node.js-specific rules.
+ */
+export const node: OxlintConfig = {
+  plugins: ['node'],
+
+  env: {
+    node: true,
+  },
+
+  rules: {
+    'node/no-exports-assign': 'error',
+    'node/no-new-require': 'error',
+  },
+};

configs/oxlint/src/presets/typescript.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * TypeScript-specific rules.
+ *
+ * Applied via `overrides` for `*.ts`, `*.tsx`, `*.mts`, `*.cts` files.
+ */
+export const typescript: OxlintConfig = {
+  plugins: ['typescript'],
+
+  overrides: [
+    {
+      files: ['**/*.ts', '**/*.tsx', '**/*.mts', '**/*.cts'],
+      rules: {
+        'typescript/consistent-type-imports': 'error',
+        'typescript/no-explicit-any': 'off',
+        'typescript/no-non-null-assertion': 'off',
+        'typescript/prefer-as-const': 'error',
+        'typescript/no-empty-object-type': 'warn',
+        'typescript/no-wrapper-object-types': 'error',
+        'typescript/no-duplicate-enum-values': 'error',
+        'typescript/no-unsafe-declaration-merging': 'error',
+        'typescript/no-import-type-side-effects': 'error',
+        'typescript/no-useless-empty-export': 'warn',
+        'typescript/no-inferrable-types': 'warn',
+        'typescript/prefer-function-type': 'warn',
+        'typescript/ban-tslint-comment': 'error',
+        'typescript/consistent-type-definitions': ['warn', 'interface'],
+        'typescript/prefer-for-of': 'warn',
+        'typescript/no-unnecessary-type-constraint': 'warn',
+        'typescript/adjacent-overload-signatures': 'warn',
+        'typescript/array-type': ['warn', { default: 'array-simple' }],
+        'typescript/no-this-alias': 'error',
+        'typescript/triple-slash-reference': 'error',
+        'typescript/no-namespace': 'error',
+      },
+    },
+  ],
+};

configs/oxlint/src/presets/vitest.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * Vitest rules for test files.
+ *
+ * Applied via `overrides` for common test file patterns.
+ */
+export const vitest: OxlintConfig = {
+  plugins: ['vitest'],
+
+  overrides: [
+    {
+      files: [
+        '**/*.test.{ts,tsx,js,jsx}',
+        '**/*.spec.{ts,tsx,js,jsx}',
+        '**/test/**/*.{ts,tsx,js,jsx}',
+        '**/__tests__/**/*.{ts,tsx,js,jsx}',
+      ],
+      rules: {
+        'vitest/no-conditional-tests': 'warn',
+        'vitest/no-import-node-test': 'error',
+        'vitest/prefer-to-be-truthy': 'warn',
+        'vitest/prefer-to-be-falsy': 'warn',
+        'vitest/prefer-to-be-object': 'warn',
+        'vitest/prefer-to-have-length': 'warn',
+        'vitest/consistent-test-filename': 'warn',
+        'vitest/prefer-describe-function-title': 'warn',
+
+        /* relax strict rules in tests */
+        'eslint/no-unused-vars': 'off',
+        'typescript/no-explicit-any': 'off',
+      },
+    },
+  ],
+};

configs/oxlint/src/presets/vue.ts

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+import type { OxlintConfig } from '../types';
+
+/**
+ * Vue.js-specific rules.
+ *
+ * Enforces Composition API with `<script setup>` and type-based declarations.
+ */
+export const vue: OxlintConfig = {
+  plugins: ['vue'],
+
+  rules: {
+    'vue/no-arrow-functions-in-watch': 'error',
+    'vue/no-deprecated-destroyed-lifecycle': 'error',
+    'vue/no-export-in-script-setup': 'error',
+    'vue/no-lifecycle-after-await': 'error',
+    'vue/no-multiple-slot-args': 'error',
+    'vue/no-import-compiler-macros': 'error',
+    'vue/define-emits-declaration': ['error', 'type-based'],
+    'vue/define-props-declaration': ['error', 'type-based'],
+    'vue/prefer-import-from-vue': 'error',
+    'vue/no-required-prop-with-default': 'warn',
+    'vue/valid-define-emits': 'error',
+    'vue/valid-define-props': 'error',
+    'vue/require-typed-ref': 'warn',
+  },
+};

configs/oxlint/src/types.ts

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+/**
+ * Re-exported configuration types from `oxlint`.
+ *
+ * Keeps the preset API in sync with the oxlint CLI without
+ * maintaining a separate copy of the types.
+ *
+ * @see https://oxc.rs/docs/guide/usage/linter/config-file-reference.html
+ */
+export type {
+  OxlintConfig,
+  OxlintOverride,
+  OxlintEnv,
+  OxlintGlobals,
+  AllowWarnDeny,
+  DummyRule,
+  DummyRuleMap,
+  RuleCategories,
+} from 'oxlint';