test: add tests for recommended rule set

README.md

@@ -12,28 +12,31 @@ Install the config along with its peer dependencies, `eslint` and `prettier`:
 npm install -D eslint-config-scratch eslint@^9 prettier@^3
 ```
 
-Add `eslint.config.mjs` to your project root and, optionally, configure parser options for rules that require type
-information:
+Add `eslint.config.mjs` to your project root.
+
+For a TypeScript project, you can add `languageOptions` to enable type checking:
 
 ```js
 // myProjectRoot/eslint.config.mjs
 import { eslintConfigScratch } from 'eslint-config-scratch'
 
-// for plain JavaScript:
-export default eslintConfigScratch.recommended
-
-// for a TypeScript project:
-export default eslintConfigScratch.config(
-  eslintConfigScratch.recommended,
-  {
-    languageOptions: {
-      parserOptions: {
-        projectService: true,
-        tsconfigRootDir: import.meta.dirname,
-      },
-    }
+export default eslintConfigScratch.config(eslintConfigScratch.recommended, {
+  languageOptions: {
+    parserOptions: {
+      projectService: true,
+      tsconfigRootDir: import.meta.dirname,
+    },
   },
-)
+})
+```
+
+For a JavaScript project, it might look like this:
+
+```js
+// myProjectRoot/eslint.config.mjs
+import { eslintConfigScratch } from 'eslint-config-scratch'
+
+export default eslintConfigScratch.recommended
 ```
 
 The function `eslintConfigScratch.config` is a re-export of the `config` function from `typescript-eslint`, and helps

eslint.config.mjs

@@ -1,8 +1,13 @@
+import { globalIgnores } from 'eslint/config'
 import globals from 'globals'
 import { eslintConfigScratch } from './lib/index.mjs'
 
-export default eslintConfigScratch.config(eslintConfigScratch.recommended, {
-  languageOptions: {
-    globals: globals.node,
+export default eslintConfigScratch.config(
+  eslintConfigScratch.recommended,
+  {
+    languageOptions: {
+      globals: globals.node,
+    },
   },
-})
+  globalIgnores(['test/**/*.bad.*']),
+)

package.json

@@ -6,8 +6,9 @@
   "scripts": {
     "prepare": "husky install",
     "format": "prettier --write . && eslint --fix",
-    "lint": "eslint && prettier --check .",
-    "test": "npm run lint"
+    "test:lint": "eslint && prettier --check .",
+    "test:vitest": "vitest run",
+    "test": "npm run test:lint && npm run test:vitest"
   },
   "repository": {
     "type": "git",
@@ -54,7 +55,8 @@
     "eslint": "9.25.1",
     "husky": "8.0.3",
     "scratch-semantic-release-config": "3.0.0",
-    "semantic-release": "24.2.3"
+    "semantic-release": "24.2.3",
+    "vitest": "^3.1.1"
   },
   "config": {
     "commitizen": {

test/__snapshots__/eslint.test.mjs.snap

@@ -0,0 +1,112 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`'recommended' > Plain TS (bad) 1`] = `
+[
+  {
+    "column": 7,
+    "endColumn": 25,
+    "endLine": 5,
+    "line": 5,
+    "messageId": "noInferrableType",
+    "nodeType": "VariableDeclarator",
+    "ruleId": "@typescript-eslint/no-inferrable-types",
+  },
+  {
+    "column": 7,
+    "endColumn": 12,
+    "endLine": 5,
+    "line": 5,
+    "messageId": "unusedVar",
+    "nodeType": null,
+    "ruleId": "@typescript-eslint/no-unused-vars",
+  },
+  {
+    "column": 10,
+    "endColumn": 13,
+    "endLine": 8,
+    "line": 8,
+    "messageId": "unusedVar",
+    "nodeType": null,
+    "ruleId": "@typescript-eslint/no-unused-vars",
+  },
+  {
+    "column": 14,
+    "endColumn": 26,
+    "endLine": 17,
+    "line": 17,
+    "messageId": "anyAssignment",
+    "nodeType": "VariableDeclarator",
+    "ruleId": "@typescript-eslint/no-unsafe-assignment",
+  },
+  {
+    "column": 20,
+    "endColumn": 24,
+    "endLine": 17,
+    "line": 17,
+    "messageId": "unsafeCall",
+    "nodeType": "Identifier",
+    "ruleId": "@typescript-eslint/no-unsafe-call",
+  },
+]
+`;
+
+exports[`'recommended' > Plain TS (good) 1`] = `[]`;
+
+exports[`'recommended' > React JSX (bad) 1`] = `
+[
+  {
+    "column": 10,
+    "endColumn": 13,
+    "endLine": 4,
+    "line": 4,
+    "messageId": "unusedVar",
+    "nodeType": "Identifier",
+    "ruleId": "no-unused-vars",
+  },
+  {
+    "column": 20,
+    "endColumn": 24,
+    "endLine": 14,
+    "line": 14,
+    "messageId": "undef",
+    "nodeType": "Identifier",
+    "ruleId": "no-undef",
+  },
+]
+`;
+
+exports[`'recommended' > React JSX (good) 1`] = `[]`;
+
+exports[`'recommended' > plain JS (bad) 1`] = `
+[
+  {
+    "column": 10,
+    "endColumn": 13,
+    "endLine": 4,
+    "line": 4,
+    "messageId": "unusedVar",
+    "nodeType": "Identifier",
+    "ruleId": "no-unused-vars",
+  },
+  {
+    "column": 26,
+    "endColumn": 46,
+    "endLine": 12,
+    "line": 12,
+    "messageId": "noJSXWithExtension",
+    "nodeType": "JSXElement",
+    "ruleId": "react/jsx-filename-extension",
+  },
+  {
+    "column": 20,
+    "endColumn": 24,
+    "endLine": 15,
+    "line": 15,
+    "messageId": "undef",
+    "nodeType": "Identifier",
+    "ruleId": "no-undef",
+  },
+]
+`;
+
+exports[`'recommended' > plain JS (good) 1`] = `[]`;

test/eslint.test.mjs

@@ -0,0 +1,110 @@
+import { ESLint } from 'eslint'
+import path from 'path'
+import util from 'util'
+import { beforeAll, describe, expect, test } from 'vitest'
+
+/**
+ * @typedef {object} EslintTestInfo
+ * @property {string} name - the title/message for this test
+ * @property {string} filePath - the path to the file to lint
+ * @property {number} warningCount - the number of warnings to expect
+ * @property {number} errorCount - the number of errors to expect
+ */
+
+// TSX is omitted because TypeScript insists on fully knowing the React types,
+// and I would rather not add React as a dependency of eslint-config-scratch.
+/** @type {Record<string, EslintTestInfo[]>} */
+const testInfo = {
+  recommended: [
+    {
+      name: 'plain JS (good)',
+      filePath: 'plain.good.mjs',
+      warningCount: 0,
+      errorCount: 0,
+    },
+    {
+      name: 'React JSX (good)',
+      filePath: 'react.good.jsx',
+      warningCount: 0,
+      errorCount: 0,
+    },
+    {
+      name: 'plain JS (bad)',
+      filePath: 'plain.bad.mjs',
+      warningCount: 0,
+      errorCount: 3,
+    },
+    {
+      name: 'React JSX (bad)',
+      filePath: 'react.bad.jsx',
+      warningCount: 0,
+      errorCount: 2,
+    },
+    {
+      name: 'Plain TS (good)',
+      filePath: 'plain.good.ts',
+      warningCount: 0,
+      errorCount: 0,
+    },
+    {
+      name: 'Plain TS (bad)',
+      filePath: 'plain.bad.ts',
+      warningCount: 0,
+      errorCount: 5,
+    },
+  ],
+}
+
+/**
+ * Create a snapshot of a lint message.
+ * Excludes properties that may change without affecting correctness, such as human-readable text.
+ * @param {ESLint.LintMessage} result - the lint message to filter
+ * @returns {object} a filtered snapshot of the lint message
+ */
+const messageSnapshot = result =>
+  Object.fromEntries(
+    Object.entries(result).filter(([k]) =>
+      ['line', 'column', 'endLine', 'endColumn', 'messageId', 'nodeType', 'ruleId'].includes(k),
+    ),
+  )
+
+test('make sure eslint works at all', async () => {
+  const source = 'foo(42)'
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  const results = await eslint.lintText(source)
+  expect(results).toBeDefined()
+  expect(results.length).toBe(1)
+  expect(results[0].warningCount).toEqual(0)
+  expect(results[0].errorCount).toEqual(0)
+})
+
+describe.concurrent.for(Object.entries(testInfo))('$0', ([subdir, testList]) => {
+  /**
+   * @type {ESLint.LintResult[]}
+   */
+  let results
+
+  // Linting one file at a time takes much longer
+  beforeAll(async () => {
+    const eslint = new ESLint({
+      overrideConfigFile: path.resolve(import.meta.dirname, subdir, 'eslint.config.mjs'),
+    })
+    results = await eslint.lintFiles(testList.map(info => path.resolve(import.meta.dirname, subdir, info.filePath)))
+  })
+
+  test('results container', () => {
+    expect(results).toBeDefined()
+    expect(results.length).toBe(testList.length)
+  })
+
+  testList.forEach(({ name, filePath, warningCount, errorCount }, i) => {
+    test(name, () => {
+      expect(path.resolve(results[i].filePath)).toBe(path.resolve(import.meta.dirname, subdir, filePath))
+      expect(results[i].warningCount, util.inspect(results[i])).toBe(warningCount)
+      expect(results[i].errorCount, util.inspect(results[i])).toBe(errorCount)
+      expect(results[i].messages.map(messageSnapshot), util.inspect(results[i].messages)).toMatchSnapshot()
+    })
+  })
+})

test/recommended/eslint.config.mjs

@@ -0,0 +1,14 @@
+import { eslintConfigScratch } from '../../lib/index.mjs'
+
+const config = eslintConfigScratch.config(eslintConfigScratch.recommended, {
+  files: ['**/*.ts', '**/*.tsx'],
+  languageOptions: {
+    parserOptions: {
+      projectService: true,
+      tsconfigRootDir: import.meta.dirname,
+      project: ['./tsconfig.json'],
+    },
+  },
+})
+
+export default config

test/recommended/plain.bad.mjs

@@ -0,0 +1,15 @@
+import ESLint from 'eslint'
+
+// foo isn't used
+function foo() {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+// React isn't allowed in plain JS
+export const myElement = <div>{'hello'}</div>
+
+// foo2 isn't defined
+export const bar = foo2()

test/recommended/plain.bad.ts

@@ -0,0 +1,17 @@
+import { ESLint } from 'eslint'
+
+// @typescript-eslint/no-inferrable-types
+// @typescript-eslint/no-unused-vars
+const forty: number = 40
+
+// @typescript-eslint/no-unused-vars
+function foo(): ESLint {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+// @typescript-eslint/no-unsafe-call (`foo2` is an error-typed value)
+// @typescript-eslint/no-unsafe-assignment (`foo2()` is an error-typed value)
+export const bar = foo2()

test/recommended/plain.good.mjs

@@ -0,0 +1,10 @@
+import ESLint from 'eslint'
+
+function foo() {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+export const bar = foo()

test/recommended/plain.good.ts

@@ -0,0 +1,10 @@
+import { ESLint } from 'eslint'
+
+function foo(): ESLint {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+export const bar = foo()

test/recommended/react.bad.jsx

@@ -0,0 +1,14 @@
+import ESLint from 'eslint'
+
+// foo isn't used
+function foo() {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+export const myElement = <div>{'hello'}</div>
+
+// foo2 isn't defined
+export const bar = foo2()

test/recommended/react.good.jsx

@@ -0,0 +1,12 @@
+import ESLint from 'eslint'
+
+function foo() {
+  const eslint = new ESLint({
+    overrideConfigFile: true,
+  })
+  return eslint
+}
+
+export const myElement = <div>{'hello'}</div>
+
+export const bar = foo()

test/recommended/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "compilerOptions": {
+    "strict": true
+  },
+  "include": ["**/*.ts", "**/*.tsx"]
+}