feat(rule): add no-hooks rule (#74)

Resolves #72

Author: macklinu

README.md

@@ -83,6 +83,7 @@ for more information about extending configuration files.
 | [consistent-test-it](docs/rules/consistent-test-it.md)             | Enforce consistent test or it keyword                           |                                                                         | ![fixable](https://img.shields.io/badge/-fixable-green.svg) |
 | [no-disabled-tests](docs/rules/no-disabled-tests.md)               | Disallow disabled tests                                         | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-focused-tests](docs/rules/no-focused-tests.md)                 | Disallow focused tests                                          | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
+| [no-hooks](docs/rules/no-hooks.md)                                 | Disallow setup and teardown hooks                               |                                                                         |                                                             |
 | [no-identical-title](docs/rules/no-identical-title.md)             | Disallow identical titles                                       | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-large-snapshots](docs/rules/no-large-snapshots.md)             | Disallow large snapshots                                        |                                                                         |                                                             |
 | [prefer-to-have-length](docs/rules/prefer-to-have-length.md)       | Suggest using `toHaveLength()`                                  | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) | ![fixable](https://img.shields.io/badge/-fixable-green.svg) |

docs/rules/no-hooks.md

@@ -0,0 +1,175 @@
+# Disallow setup and teardown hooks (no-hooks)
+
+Jest provides global functions for setup and teardown tasks, which are called
+before/after each test case and each test suite. The use of these hooks promotes
+shared state between tests.
+
+## Rule Details
+
+This rule reports for the following function calls:
+
+* `beforeAll`
+* `beforeEach`
+* `afterAll`
+* `afterEach`
+
+Examples of **incorrect** code for this rule:
+
+```js
+/* eslint jest/no-hooks: "error" */
+
+function setupFoo(options) {
+  /* ... */
+}
+
+function setupBar(options) {
+  /* ... */
+}
+
+describe('foo', () => {
+  let foo;
+
+  beforeEach(() => {
+    foo = setupFoo();
+  });
+
+  afterEach(() => {
+    foo = null;
+  });
+
+  it('does something', () => {
+    expect(foo.doesSomething()).toBe(true);
+  });
+
+  describe('with bar', () => {
+    let bar;
+
+    beforeEach(() => {
+      bar = setupBar();
+    });
+
+    afterEach(() => {
+      bar = null;
+    });
+
+    it('does something with bar', () => {
+      expect(foo.doesSomething(bar)).toBe(true);
+    });
+  });
+});
+```
+
+Examples of **correct** code for this rule:
+
+```js
+/* eslint jest/no-hooks: "error" */
+
+function setupFoo(options) {
+  /* ... */
+}
+
+function setupBar(options) {
+  /* ... */
+}
+
+describe('foo', () => {
+  it('does something', () => {
+    const foo = setupFoo();
+    expect(foo.doesSomething()).toBe(true);
+  });
+
+  it('does something with bar', () => {
+    const foo = setupFoo();
+    const bar = setupBar();
+    expect(foo.doesSomething(bar)).toBe(true);
+  });
+});
+```
+
+## Options
+
+```json
+{
+  "jest/no-hooks": [
+    "error",
+    {
+      "allow": ["afterEach", "afterAll"]
+    }
+  ]
+}
+```
+
+### `allow`
+
+This array option whitelists setup and teardown hooks so that this rule does not
+report their usage as being incorrect. There are four possible values:
+
+* `"beforeAll"`
+* `"beforeEach"`
+* `"afterAll"`
+* `"afterEach"`
+
+By default, none of these options are enabled (the equivalent of
+`{ "allow": [] }`).
+
+Examples of **incorrect** code for the `{ "allow": ["afterEach"] }` option:
+
+```js
+/* eslint jest/no-hooks: ["error", { "allow": ["afterEach"] }] */
+
+function setupFoo(options) {
+  /* ... */
+}
+
+let foo;
+
+beforeEach(() => {
+  foo = setupFoo();
+});
+
+afterEach(() => {
+  jest.resetModules();
+});
+
+test('foo does this', () => {
+  // ...
+});
+
+test('foo does that', () => {
+  // ...
+});
+```
+
+Examples of **correct** code for the `{ "allow": ["afterEach"] }` option:
+
+```js
+/* eslint jest/no-hooks: ["error", { "allow": ["afterEach"] }] */
+
+function setupFoo(options) {
+  /* ... */
+}
+
+afterEach(() => {
+  jest.resetModules();
+});
+
+test('foo does this', () => {
+  const foo = setupFoo();
+  // ...
+});
+
+test('foo does that', () => {
+  const foo = setupFoo();
+  // ...
+});
+```
+
+## When Not To Use It
+
+If you prefer using the setup and teardown hooks provided by Jest, you can
+safely disable this rule.
+
+## Further Reading
+
+* [Jest docs - Setup and Teardown](https://facebook.github.io/jest/docs/en/setup-teardown.html)
+* [@jamiebuilds Twitter thread](https://twitter.com/jamiebuilds/status/954906997169664000)

index.js

@@ -3,6 +3,7 @@
 const consistentTestIt = require('./rules/consistent-test-it');
 const noDisabledTests = require('./rules/no-disabled-tests');
 const noFocusedTests = require('./rules/no-focused-tests');
+const noHooks = require('./rules/no-hooks');
 const noIdenticalTitle = require('./rules/no-identical-title');
 const noLargeSnapshots = require('./rules/no-large-snapshots');
 const preferToBeNull = require('./rules/prefer-to-be-null');
@@ -61,6 +62,7 @@ module.exports = {
     'consistent-test-it': consistentTestIt,
     'no-disabled-tests': noDisabledTests,
     'no-focused-tests': noFocusedTests,
+    'no-hooks': noHooks,
     'no-identical-title': noIdenticalTitle,
     'no-large-snapshots': noLargeSnapshots,
     'prefer-to-be-null': preferToBeNull,

rules/__tests__/no-hooks.test.js

@@ -0,0 +1,44 @@
+'use strict';
+
+const RuleTester = require('eslint').RuleTester;
+const rules = require('../..').rules;
+const ruleTester = new RuleTester({
+  parserOptions: {
+    ecmaVersion: 6,
+  },
+});
+
+ruleTester.run('no-hooks', rules['no-hooks'], {
+  valid: [
+    'test("foo")',
+    'describe("foo", () => { it("bar") })',
+    'test("foo", () => { expect(subject.beforeEach()).toBe(true) })',
+    {
+      code: 'afterEach(() => {}); afterAll(() => {});',
+      options: [{ allow: ['afterEach', 'afterAll'] }],
+    },
+  ],
+  invalid: [
+    {
+      code: 'beforeAll(() => {})',
+      errors: [{ message: "Unexpected 'beforeAll' hook" }],
+    },
+    {
+      code: 'beforeEach(() => {})',
+      errors: [{ message: "Unexpected 'beforeEach' hook" }],
+    },
+    {
+      code: 'afterAll(() => {})',
+      errors: [{ message: "Unexpected 'afterAll' hook" }],
+    },
+    {
+      code: 'afterEach(() => {})',
+      errors: [{ message: "Unexpected 'afterEach' hook" }],
+    },
+    {
+      code: 'beforeEach(() => {}); afterEach(() => { jest.resetModules() });',
+      options: [{ allow: ['afterEach'] }],
+      errors: [{ message: "Unexpected 'beforeEach' hook" }],
+    },
+  ],
+});

rules/no-hooks.js

@@ -0,0 +1,52 @@
+'use strict';
+
+module.exports = {
+  meta: {
+    docs: {
+      url:
+        'https://github.com/jest-community/eslint-plugin-jest/blob/master/docs/rules/no-hooks.md',
+    },
+  },
+  schema: [
+    {
+      type: 'object',
+      properties: {
+        allow: {
+          type: 'array',
+          contains: ['beforeAll', 'beforeEach', 'afterAll', 'afterEach'],
+        },
+      },
+      additionalProperties: false,
+    },
+  ],
+  create(context) {
+    const testHookNames = Object.assign(Object.create(null), {
+      beforeAll: true,
+      beforeEach: true,
+      afterAll: true,
+      afterEach: true,
+    });
+
+    const whitelistedHookNames = (
+      context.options[0] || { allow: [] }
+    ).allow.reduce((hashMap, value) => {
+      hashMap[value] = true;
+      return hashMap;
+    }, Object.create(null));
+
+    const isHook = node => testHookNames[node.callee.name];
+    const isWhitelisted = node => whitelistedHookNames[node.callee.name];
+
+    return {
+      CallExpression(node) {
+        if (isHook(node) && !isWhitelisted(node)) {
+          context.report({
+            node,
+            message: "Unexpected '{{ hookName }}' hook",
+            data: { hookName: node.callee.name },
+          });
+        }
+      },
+    };
+  },
+};