feat(linter/plugins): implement context.languageOptions (#15486)

Implement `Context#languageOptions`.

Author: overlookmotel

apps/oxlint/src-js/index.ts

@@ -3,7 +3,14 @@ import type { CreateOnceRule, Plugin, Rule } from './plugins/load.ts';
 import type { BeforeHook, Visitor, VisitorWithHooks } from './plugins/types.ts';
 
 export type * as ESTree from './generated/types.d.ts';
-export type { Context, Diagnostic, DiagnosticBase, DiagnosticWithLoc, DiagnosticWithNode } from './plugins/context.ts';
+export type {
+  Context,
+  Diagnostic,
+  DiagnosticBase,
+  DiagnosticWithLoc,
+  DiagnosticWithNode,
+  LanguageOptions,
+} from './plugins/context.ts';
 export type { Fix, Fixer, FixFn } from './plugins/fix.ts';
 export type { CreateOnceRule, CreateRule, Plugin, Rule } from './plugins/load.ts';
 export type {

apps/oxlint/src-js/plugins/context.ts

@@ -28,13 +28,14 @@
 
 import { getFixes } from './fix.js';
 import { getOffsetFromLineColumn } from './location.js';
-import { SOURCE_CODE } from './source_code.js';
+import { ast, initAst, SOURCE_CODE } from './source_code.js';
 import { settings, initSettings } from './settings.js';
 
 import type { Fix, FixFn } from './fix.ts';
 import type { RuleDetails } from './load.ts';
 import type { SourceCode } from './source_code.ts';
 import type { Location, Ranged } from './types.ts';
+import type { ModuleKind } from '../generated/types.d.ts';
 
 const { hasOwn, keys: ObjectKeys, freeze, assign: ObjectAssign, create: ObjectCreate } = Object;
 
@@ -94,6 +95,70 @@ export function resetFileContext(): void {
   filePath = null;
 }
 
+// ECMAScript version. This matches ESLint's default.
+const ECMA_VERSION = 2026;
+
+// Singleton object for parser options.
+const PARSER_OPTIONS = freeze({
+  /**
+   * Source type of the file being linted.
+   */
+  get sourceType(): ModuleKind {
+    // TODO: Would be better to get `sourceType` without deserializing whole AST,
+    // in case it's used in `create` to return an empty visitor if wrong type.
+    // TODO: ESLint also has `commonjs` option.
+    if (ast === null) initAst();
+    return ast.sourceType;
+  },
+});
+
+// Singleton object for language options.
+const LANGUAGE_OPTIONS = freeze({
+  /**
+   * Source type of the file being linted.
+   */
+  get sourceType(): ModuleKind {
+    // TODO: Would be better to get `sourceType` without deserializing whole AST,
+    // in case it's used in `create` to return an empty visitor if wrong type.
+    // TODO: ESLint also has `commonjs` option.
+    if (ast === null) initAst();
+    return ast.sourceType;
+  },
+
+  /**
+   * ECMAScript version of the file being linted.
+   */
+  ecmaVersion: ECMA_VERSION,
+
+  /**
+   * Parser used to parse the file being linted.
+   */
+  get parser(): Record<string, unknown> {
+    throw new Error('`context.languageOptions.parser` is not implemented yet.'); // TODO
+  },
+
+  /**
+   * Parser options used to parse the file being linted.
+   */
+  parserOptions: PARSER_OPTIONS,
+
+  /**
+   * Globals defined for the file being linted.
+   */
+  // ESLint has `globals` as `null`, not empty object, if no globals are defined.
+  get globals(): Record<string, 'readonly' | 'writable' | 'off'> | null {
+    // TODO: Get globals from Rust side.
+    // Note: ESLint's type is "writable", whereas Oxlint's is "writeable" (misspelled with extra "e").
+    // Probably we should fix that on Rust side (while still allowing "writeable").
+    return null;
+  },
+});
+
+/**
+ * Language options used when parsing a file.
+ */
+export type LanguageOptions = typeof LANGUAGE_OPTIONS;
+
 // Singleton object for file-specific properties.
 //
 // Only one file is linted at a time, so we reuse a single object for all files.
@@ -140,9 +205,9 @@ const FILE_CONTEXT = freeze({
   /**
    * Language options used when parsing this file.
    */
-  get languageOptions(): Record<string, unknown> {
+  get languageOptions(): LanguageOptions {
     if (filePath === null) throw new Error('Cannot access `context.languageOptions` in `createOnce`');
-    throw new Error('`context.languageOptions` is not implemented yet.'); // TODO
+    return LANGUAGE_OPTIONS;
   },
 
   /**

apps/oxlint/test/e2e.test.ts

@@ -190,6 +190,10 @@ describe('oxlint CLI', () => {
     await testFixture('sourceCode_scope_methods');
   });
 
+  it('should support languageOptions', async () => {
+    await testFixture('languageOptions');
+  });
+
   it('should support selectors', async () => {
     await testFixture('selector');
   });

apps/oxlint/test/fixtures/languageOptions/.oxlintrc.json

@@ -0,0 +1,9 @@
+{
+  "jsPlugins": ["./plugin.ts"],
+  "categories": {
+    "correctness": "off"
+  },
+  "rules": {
+    "language-options-plugin/lang": "error"
+  }
+}

apps/oxlint/test/fixtures/languageOptions/files/index.cjs

@@ -0,0 +1 @@
+let x;

apps/oxlint/test/fixtures/languageOptions/files/index.js

@@ -0,0 +1 @@
+let x;

apps/oxlint/test/fixtures/languageOptions/files/index.mjs

@@ -0,0 +1 @@
+let x;

apps/oxlint/test/fixtures/languageOptions/output.snap.md

@@ -0,0 +1,44 @@
+# Exit code
+1
+
+# stdout
+```
+  x language-options-plugin(lang): languageOptions:
+  | sourceType: script
+  | ecmaVersion: 2026
+  | parserOptions: {"sourceType":"script"}
+  | globals: null
+   ,-[files/index.cjs:1:1]
+ 1 | let x;
+   : ^
+   `----
+
+  x language-options-plugin(lang): languageOptions:
+  | sourceType: module
+  | ecmaVersion: 2026
+  | parserOptions: {"sourceType":"module"}
+  | globals: null
+   ,-[files/index.js:1:1]
+ 1 | let x;
+   : ^
+   `----
+
+  x language-options-plugin(lang): languageOptions:
+  | sourceType: module
+  | ecmaVersion: 2026
+  | parserOptions: {"sourceType":"module"}
+  | globals: null
+   ,-[files/index.mjs:1:1]
+ 1 | let x;
+   : ^
+   `----
+
+Found 0 warnings and 3 errors.
+Finished in Xms on 3 files using X threads.
+```
+
+# stderr
+```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
+```

apps/oxlint/test/fixtures/languageOptions/plugin.ts

@@ -0,0 +1,38 @@
+import type { Plugin, Node } from '../../../dist/index.js';
+
+const SPAN: Node = {
+  start: 0,
+  end: 0,
+  range: [0, 0],
+  loc: {
+    start: { line: 0, column: 0 },
+    end: { line: 0, column: 0 },
+  },
+};
+
+const plugin: Plugin = {
+  meta: {
+    name: 'language-options-plugin',
+  },
+  rules: {
+    lang: {
+      create(context) {
+        const { languageOptions } = context;
+
+        context.report({
+          message:
+            'languageOptions:\n' +
+            `sourceType: ${languageOptions.sourceType}\n` +
+            `ecmaVersion: ${languageOptions.ecmaVersion}\n` +
+            `parserOptions: ${JSON.stringify(languageOptions.parserOptions)}\n` +
+            `globals: ${JSON.stringify(languageOptions.globals)}`,
+          node: SPAN,
+        });
+
+        return {};
+      },
+    },
+  },
+};
+
+export default plugin;