chore: document package.json integration

README.md

@@ -75,6 +75,57 @@ Copying these rules into your `rules` object will achieve the same effect as usi
 > Our type-aware rules depend on TypeScript ESLint's parser, which means they
 > will not work with oxlint at this time.
 
+## Linting `package.json`
+
+Some rules (e.g. `ban-dependencies`) can be used against your `package.json`.
+
+You can achieve this by using `@eslint/json` or `jsonc-eslint-parser`.
+
+For example, with `@eslint/json` and `eslint.config.js`:
+
+```ts
+import e18e from '@e18e/eslint-plugin';
+import json from '@eslint/json';
+import {defineConfig} from 'eslint/config';
+
+export default defineConfig([
+  {
+    files: ['package.json'],
+    language: 'json/json',
+    plugins: {
+      e18e,
+      json
+    },
+    extends: ['e18e/recommended'],
+  }
+]);
+```
+
+Or with `jsonc-eslint-parser` and `eslint.config.js`:
+
+```ts
+import e18e from '@e18e/eslint-plugin';
+import jsonParser from 'jsonc-eslint-parser';
+import {defineConfig} from 'eslint/config';
+
+export default defineConfig([
+  {
+    files: ['package.json'],
+    languageOptions: {
+      parser: jsonParser
+    },
+    plugins: {
+      e18e
+    },
+    extends: ['e18e/recommended'],
+  }
+]);
+```
+
+Read more at the
+[`@eslint/json` docs](https://github.com/eslint/json) and
+[`jsonc-eslint-parser` docs](https://github.com/ota-meshi/jsonc-eslint-parser).
+
 ## Rules
 
 **Legend:**

package.json

@@ -36,12 +36,14 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.2",
+    "@eslint/json": "^0.14.0",
     "@types/node": "^25.0.6",
     "@typescript-eslint/rule-tester": "^8.52.0",
     "@typescript-eslint/typescript-estree": "^8.52.0",
     "@vitest/coverage-v8": "^4.0.16",
     "eslint": "^9.39.2",
     "eslint-plugin-eslint-plugin": "^7.3.0",
+    "jsonc-eslint-parser": "^2.4.2",
     "oxlint": "^1.38.0",
     "prettier": "^3.7.4",
     "typescript": "^5.9.3",

src/main.test.ts

@@ -0,0 +1,58 @@
+import {describe, it, expect} from 'vitest';
+import {ESLint, type Linter} from 'eslint';
+import jsoncParser from 'jsonc-eslint-parser';
+import json from '@eslint/json';
+import plugin from './main.js';
+
+describe('main plugin', () => {
+  it('should run against JSON files using jsonc-eslint-parser', async () => {
+    const eslint = new ESLint({
+      overrideConfigFile: true,
+      overrideConfig: [
+        {
+          files: ['**/*.json'],
+          languageOptions: {
+            parser: jsoncParser
+          }
+        },
+        plugin.configs!.recommended as Linter.Config
+      ]
+    });
+
+    const results = await eslint.lintText(
+      JSON.stringify({name: 'test', version: '1.0.0'}, null, 2),
+      {filePath: 'package.json'}
+    );
+
+    expect(results).toBeDefined();
+    expect(results).toHaveLength(1);
+    expect(results[0]!.messages).toHaveLength(0);
+    expect(results[0]!.filePath).toContain('package.json');
+  });
+
+  it('should run against JSON files using @eslint/json', async () => {
+    const eslint = new ESLint({
+      overrideConfigFile: true,
+      overrideConfig: [
+        {
+          files: ['**/*.json'],
+          plugins: {
+            json
+          },
+          language: 'json/json'
+        },
+        plugin.configs!.recommended as Linter.Config
+      ]
+    });
+
+    const results = await eslint.lintText(
+      JSON.stringify({name: 'test', version: '1.0.0'}, null, 2),
+      {filePath: 'package.json'}
+    );
+
+    expect(results).toBeDefined();
+    expect(results).toHaveLength(1);
+    expect(results[0]!.messages).toHaveLength(0);
+    expect(results[0]!.filePath).toContain('package.json');
+  });
+});

src/rules/ban-dependencies.test.ts

@@ -1,5 +1,7 @@
 import {RuleTester} from 'eslint';
 import {rules} from 'eslint-plugin-depend';
+import json from '@eslint/json';
+import jsoncParser from 'jsonc-eslint-parser';
 
 const ruleTester = new RuleTester({
   languageOptions: {
@@ -8,6 +10,11 @@ const ruleTester = new RuleTester({
   }
 });
 
+const jsonRuleTester = new RuleTester({
+  language: 'json/json',
+  plugins: {json}
+});
+
 // TODO (jg): one day the ban-dependencies rule will live in this repo, so
 // we should move all the tests from the depend repo to here.
 
@@ -22,7 +29,12 @@ ruleTester.run('ban-dependencies', banDependencies, {
 
     // Built-in modules are allowed
     'import path from "path"',
-    'import {readFile} from "fs/promises"'
+    'import {readFile} from "fs/promises"',
+    {
+      code: `{"dependencies": {"typescript": "^5.3.2"}}`,
+      filename: 'package.json',
+      languageOptions: {parser: jsoncParser}
+    }
   ],
   invalid: [
     {
@@ -36,6 +48,28 @@ ruleTester.run('ban-dependencies', banDependencies, {
     {
       code: 'import _ from "lodash"',
       errors: [{messageId: 'documentedReplacement'}]
+    },
+    {
+      code: `{"dependencies": {"moment": "^1.0.0"}}`,
+      filename: 'package.json',
+      languageOptions: {parser: jsoncParser},
+      errors: [{messageId: 'documentedReplacement'}]
+    }
+  ]
+});
+
+jsonRuleTester.run('ban-dependencies (JSON)', banDependencies, {
+  valid: [
+    {
+      filename: 'package.json',
+      code: `{"dependencies": {"typescript": "^5.3.2"}}`
+    }
+  ],
+  invalid: [
+    {
+      filename: 'package.json',
+      code: `{"dependencies": {"moment": "^1.0.0"}}`,
+      errors: [{messageId: 'documentedReplacement'}]
     }
   ]
 });