feat(rules): no-expect-resolves (#364)

Author: eranshabi

README.md

@@ -114,6 +114,7 @@ installations requiring long-term consistency.
 | [no-disabled-tests][]        | Disallow disabled tests                                           | ![recommended][] |                     |
 | [no-duplicate-hooks][]       | Disallow duplicate hooks within a `describe` block                |                  |                     |
 | [no-empty-title][]           | Disallow empty titles                                             |                  |                     |
+| [no-expect-resolves][]       | Disallow using `expect().resolves`                                |                  |                     |
 | [no-export][]                | Disallow export from test files                                   |                  |                     |
 | [no-focused-tests][]         | Disallow focused tests                                            | ![recommended][] |                     |
 | [no-hooks][]                 | Disallow setup and teardown hooks                                 |                  |                     |
@@ -166,6 +167,7 @@ https://github.com/dangreenisrael/eslint-plugin-jest-formatting
 [no-disabled-tests]: docs/rules/no-disabled-tests.md
 [no-duplicate-hooks]: docs/rules/no-duplicate-hooks.md
 [no-empty-title]: docs/rules/no-empty-title.md
+[no-expect-resolves]: docs/rules/no-expect-resolves.md
 [no-export]: docs/rules/no-export.md
 [no-focused-tests]: docs/rules/no-focused-tests.md
 [no-hooks]: docs/rules/no-hooks.md

docs/rules/no-expect-resolves.md

@@ -0,0 +1,29 @@
+# Avoid using `expect().resolves` (no-expect-resolves)
+
+Jest allows you to test a promise resolve value using `await expect().resolves`.
+For consistency and readability this rule bans `expect().resolves` in favor of
+`expect(await promise)`.
+
+## Rule details
+
+This rule triggers a warning if `expect().resolves` is used.
+
+This rule is disabled by default.
+
+### Default configuration
+
+The following patterns is considered warning:
+
+```js
+test('some test', async () => {
+  await expect(Promise.resolve(1)).resolves.toBe(1);
+});
+```
+
+The following pattern is not considered warning:
+
+```js
+test('some test', async () => {
+  expect(await Promise.resolve(1)).toBe(1);
+});
+```

src/__tests__/rules.test.ts

@@ -4,7 +4,7 @@ import { resolve } from 'path';
 import { rules } from '../';
 
 const ruleNames = Object.keys(rules);
-const numberOfRules = 37;
+const numberOfRules = 38;
 
 describe('rules', () => {
   it('should have a corresponding doc for each rule', () => {

src/rules/__tests__/no-expect-resolves.test.ts

@@ -0,0 +1,24 @@
+import { TSESLint } from '@typescript-eslint/experimental-utils';
+import rule from '../no-expect-resolves';
+
+const ruleTester = new TSESLint.RuleTester({
+  parserOptions: {
+    ecmaVersion: 2017,
+  },
+});
+
+ruleTester.run('no-expect-resolves', rule, {
+  valid: [
+    `test('some test', async () => {
+         expect(await Promise.resolve(1)).toBe(1);
+     });`,
+  ],
+  invalid: [
+    {
+      code: `test('some test', async () => {
+             await expect(Promise.resolve(1)).resolves.toBe(1);
+         });`,
+      errors: [{ endColumn: 55, column: 47, messageId: 'expectResolves' }],
+    },
+  ],
+});

src/rules/no-expect-resolves.ts

@@ -0,0 +1,40 @@
+import {
+  AST_NODE_TYPES,
+  TSESTree,
+} from '@typescript-eslint/experimental-utils';
+import { createRule, isExpectCall } from './tsUtils';
+
+function isIdentifierResolves(node: TSESTree.MemberExpression) {
+  return (
+    node.property.type === AST_NODE_TYPES.Identifier &&
+    node.property.name === 'resolves'
+  );
+}
+
+function isExpectResolves(node: TSESTree.MemberExpression) {
+  return isExpectCall(node.object) && isIdentifierResolves(node);
+}
+
+export default createRule({
+  name: __filename,
+  meta: {
+    docs: {
+      category: 'Best Practices',
+      description: 'Disallow expect.resolves',
+      recommended: false,
+    },
+    messages: {
+      expectResolves: 'Use `expect(await promise)` instead.',
+    },
+    schema: [],
+    type: 'suggestion',
+  },
+  defaultOptions: [],
+  create: context => ({
+    MemberExpression(node) {
+      if (isExpectResolves(node)) {
+        context.report({ node: node.property, messageId: 'expectResolves' });
+      }
+    },
+  }),
+});