Repository: jest-community/eslint-plugin-jest (ts)

Issue:
[new rule] prefer `await expect(...).resolves`
Pretty much the opposite to the now-deprecated `no-expect-resolves`: prefer doing `await expect(...).resolves` over `expect(await ...)` as it gives a better failure message.

With `resolves`, if the promise rejects it'll fail the assertion, giving you an error on the lines of `expected promise to resolve but it rejected with ...`.
`expect(await ...)` however means that the rejection will be thrown "outside" of the `expect`, giving you a more generic "test thrown an unexpected error" message.

This also affected the behaviour of `expect.hasAssertions` & co, as with `resolves` you'll be hitting an assertion which fails, which is considered a "pass` in the eyes of `hasAssertions`.

I think `prefer-expect-resolves` could be a good name for this new rule.

Pull request:
feat: create `prefer-expect-resolves` rule
Resolves #803

I'd love to have a fixer, but `jest` kept giving me this:

```
(node:5300) UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'Node'
    |     property 'callee' -> object with constructor 'Node'
    --- property 'parent' closes the circle
    at stringify (<anonymous>)
    at writeChannelMessage (internal/child_process/serialization.js:117:20)
    at process.target._send (internal/child_process.js:805:17)
    at process.target.send (internal/child_process.js:703:19)
    at reportSuccess (/c/Users/G-Rath/workspace/projects-oss/eslint-plugin-jest/node_modules/jest-worker/build/workers/processChild.js:67:11)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:5300) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:5300) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
```

so will leave it as-is for now.

Patch:
diff --git a/README.md b/README.md
index 5b4a0bd..8ec411f 100644
--- a/README.md
+++ b/README.md
@@ -150,50 +150,51 @@ installations requiring long-term consistency.
 
 <!-- begin base rules list -->
 
-| Rule                                                                         | Description                                                     | Configurations   | Fixable      |
-| ---------------------------------------------------------------------------- | --------------------------------------------------------------- | ---------------- | ------------ |
-| [consistent-test-it](docs/rules/consistent-test-it.md)                       | Have control over `test` and `it` usages                        |                  | ![fixable][] |
-| [expect-expect](docs/rules/expect-expect.md)                                 | Enforce assertion to be made in a test body                     | ![recommended][] |              |
-| [lowercase-name](docs/rules/lowercase-name.md)                               | Enforce lowercase test names                                    |                  | ![fixable][] |
-| [max-nested-describe](docs/rules/max-nested-describe.md)                     | Enforces a maximum depth to nested describe calls               |                  |              |
-| [no-alias-methods](docs/rules/no-alias-methods.md)                           | Disallow alias methods                                          | ![style][]       | ![fixable][] |
-| [no-commented-out-tests](docs/rules/no-commented-out-tests.md)               | Disallow commented out tests                                    | ![recommended][] |              |
-| [no-conditional-expect](docs/rules/no-conditional-expect.md)                 | Prevent calling `expect` conditionally                          | ![recommended][] |              |
-| [no-deprecated-functions](docs/rules/no-deprecated-functions.md)             | Disallow use of deprecated functions                            | ![recommended][] | ![fixable][] |
-| [no-disabled-tests](docs/rules/no-disabled-tests.md)                         | Disallow disabled tests                                         | ![recommended][] |              |
-| [no-done-callback](docs/rules/no-done-callback.md)                           | Avoid using a callback in asynchronous tests and hooks          | ![recommended][] | ![suggest][] |
-| [no-duplicate-hooks](docs/rules/no-duplicate-hooks.md)                       | Disallow duplicate setup and teardown hooks                     |                  |              |
-| [no-export](docs/rules/no-export.md)                                         | Disallow using `exports` in files containing tests              | ![recommended][] |              |
-| [no-focused-tests](docs/rules/no-focused-tests.md)                           | Disallow focused tests                                          | ![recommended][] | ![suggest][] |
-| [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][] |              |
-| [no-if](docs/rules/no-if.md)                                                 | Disallow conditional logic                                      |                  |              |
-| [no-interpolation-in-snapshots](docs/rules/no-interpolation-in-snapshots.md) | Disallow string interpolation inside snapshots                  | ![recommended][] |              |
-| [no-jasmine-globals](docs/rules/no-jasmine-globals.md)                       | Disallow Jasmine globals                                        | ![recommended][] | ![fixable][] |
-| [no-jest-import](docs/rules/no-jest-import.md)                               | Disallow importing Jest                                         | ![recommended][] |              |
-| [no-large-snapshots](docs/rules/no-large-snapshots.md)                       | disallow large snapshots                                        |                  |              |
-| [no-mocks-import](docs/rules/no-mocks-import.md)                             | Disallow manually importing from `__mocks__`                    | ![recommended][] |              |
-| [no-restricted-matchers](docs/rules/no-restricted-matchers.md)               | Disallow specific matchers & modifiers                          |                  |              |
-| [no-standalone-expect](docs/rules/no-standalone-expect.md)                   | Disallow using `expect` outside of `it` or `test` blocks        | ![recommended][] |              |
-| [no-test-prefixes](docs/rules/no-test-prefixes.md)                           | Use `.only` and `.skip` over `f` and `x`                        | ![recommended][] | ![fixable][] |
-| [no-test-return-statement](docs/rules/no-test-return-statement.md)           | Disallow explicitly returning from tests                        |                  |              |
-| [prefer-called-with](docs/rules/prefer-called-with.md)                       | Suggest using `toBeCalledWith()` or `toHaveBeenCalledWith()`    |                  |              |
-| [prefer-expect-assertions](docs/rules/prefer-expect-assertions.md)           | Suggest using `expect.assertions()` OR `expect.hasAssertions()` |                  | ![suggest][] |
-| [prefer-hooks-on-top](docs/rules/prefer-hooks-on-top.md)                     | Suggest having hooks before any test cases                      |                  |              |
-| [prefer-spy-on](docs/rules/prefer-spy-on.md)                                 | Suggest using `jest.spyOn()`                                    |                  | ![fixable][] |
-| [prefer-strict-equal](docs/rules/prefer-strict-equal.md)                     | Suggest using `toStrictEqual()`                                 |                  | ![suggest][] |
-| [prefer-to-be](docs/rules/prefer-to-be.md)                                   | Suggest using `toBe()` for primitive literals                   |                  | ![fixable][] |
-| [prefer-to-be-null](docs/rules/prefer-to-be-null.md)                         | Suggest using `toBeNull()`                                      | ![style][]       | ![fixable][] |
-| [prefer-to-be-undefined](docs/rules/prefer-to-be-undefined.md)               | Suggest using `toBeUndefined()`                                 | ![style][]       | ![fixable][] |
-| [prefer-to-contain](docs/rules/prefer-to-contain.md)                         | Suggest using `toContain()`                                     | ![style][]       | ![fixable][] |
-| [prefer-to-have-length](docs/rules/prefer-to-have-length.md)                 | Suggest using `toHaveLength()`                                  | ![style][]       | ![fixable][] |
-| [prefer-todo](docs/rules/prefer-todo.md)                                     | Suggest using `test.todo`                                       |                  | ![fixable][] |
-| [require-to-throw-message](docs/rules/require-to-throw-message.md)           | Require a message for `toThrow()`                               |                  |              |
-| [require-top-level-describe](docs/rules/require-top-level-describe.md)       | Require test cases and hooks to be inside a `describe` block    |                  |              |
-| [valid-describe](docs/rules/valid-describe.md)                               | Enforce valid `describe()` callback                             | ![recommended][] |              |
-| [valid-expect](docs/rules/valid-expect.md)                                   | Enforce valid `expect()` usage                                  | ![recommended][] |              |
-| [valid-expect-in-promise](docs/rules/valid-expect-in-promise.md)             | Enforce having return statement when testing with promises      | ![recommended][] |              |
-| [valid-title](docs/rules/valid-title.md)                                     | Enforce valid titles                                            | ![recommended][] | ![fixable][] |
+| Rule                                                                         | Description                                                         | Configurations   | Fixable      |
+| ---------------------------------------------------------------------------- | ------------------------------------------------------------------- | ---------------- | ------------ |
+| [consistent-test-it](docs/rules/consistent-test-it.md)                       | Have control over `test` and `it` usages                            |                  | ![fixable][] |
+| [expect-expect](docs/rules/expect-expect.md)                                 | Enforce assertion to be made in a test body                         | ![recommended][] |              |
+| [lowercase-name](docs/rules/lowercase-name.md)                               | Enforce lowercase test names                                        |                  | ![fixable][] |
+| [max-nested-describe](docs/rules/max-nested-describe.md)                     | Enforces a maximum depth to nested describe calls                   |                  |              |
+| [no-alias-methods](docs/rules/no-alias-methods.md)                           | Disallow alias methods                                              | ![style][]       | ![fixable][] |
+| [no-commented-out-tests](docs/rules/no-commented-out-tests.md)               | Disallow commented out tests                                        | ![recommended][] |              |
+| [no-conditional-expect](docs/rules/no-conditional-expect.md)                 | Prevent calling `expect` conditionally                              | ![recommended][] |              |
+| [no-deprecated-functions](docs/rules/no-deprecated-functions.md)             | Disallow use of deprecated functions                                | ![recommended][] | ![fixable][] |
+| [no-disabled-tests](docs/rules/no-disabled-tests.md)                         | Disallow disabled tests                                             | ![recommended][] |              |
+| [no-done-callback](docs/rules/no-done-callback.md)                           | Avoid using a callback in asynchronous tests and hooks              | ![recommended][] | ![suggest][] |
+| [no-duplicate-hooks](docs/rules/no-duplicate-hooks.md)                       | Disallow duplicate setup and teardown hooks                         |                  |              |
+| [no-export](docs/rules/no-export.md)                                         | Disallow using `exports` in files containing tests                  | ![recommended][] |              |
+| [no-focused-tests](docs/rules/no-focused-tests.md)                           | Disallow focused tests                                              | ![recommended][] | ![suggest][] |
+| [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][] |              |
+| [no-if](docs/rules/no-if.md)                                                 | Disallow conditional logic                                          |                  |              |
+| [no-interpolation-in-snapshots](docs/rules/no-interpolation-in-snapshots.md) | Disallow string interpolation inside snapshots                      | ![recommended][] |              |
+| [no-jasmine-globals](docs/rules/no-jasmine-globals.md)                       | Disallow Jasmine globals                                            | ![recommended][] | ![fixable][] |
+| [no-jest-import](docs/rules/no-jest-import.md)                               | Disallow importing Jest                                             | ![recommended][] |              |
+| [no-large-snapshots](docs/rules/no-large-snapshots.md)                       | disallow large snapshots                                            |                  |              |
+| [no-mocks-import](docs/rules/no-mocks-import.md)                             | Disallow manually importing from `__mocks__`                        | ![recommended][] |              |
+| [no-restricted-matchers](docs/rules/no-restricted-matchers.md)               | Disallow specific matchers & modifiers                              |                  |              |
+| [no-standalone-expect](docs/rules/no-standalone-expect.md)                   | Disallow using `expect` outside of `it` or `test` blocks            | ![recommended][] |              |
+| [no-test-prefixes](docs/rules/no-test-prefixes.md)                           | Use `.only` and `.skip` over `f` and `x`                            | ![recommended][] | ![fixable][] |
+| [no-test-return-statement](docs/rules/no-test-return-statement.md)           | Disallow explicitly returning from tests                            |                  |              |
+| [prefer-called-with](docs/rules/prefer-called-with.md)                       | Suggest using `toBeCalledWith()` or `toHaveBeenCalledWith()`        |                  |              |
+| [prefer-expect-assertions](docs/rules/prefer-expect-assertions.md)           | Suggest using `expect.assertions()` OR `expect.hasAssertions()`     |                  | ![suggest][] |
+| [prefer-expect-resolves](docs/rules/prefer-expect-resolves.md)               | Prefer `await expect(...).resolves` over `expect(await ...)` syntax |                  | ![fixable][] |
+| [prefer-hooks-on-top](docs/rules/prefer-hooks-on-top.md)                     | Suggest having hooks before any test cases                          |                  |              |
+| [prefer-spy-on](docs/rules/prefer-spy-on.md)                                 | Suggest using `jest.spyOn()`                                        |                  | ![fixable][] |
+| [prefer-strict-equal](docs/rules/prefer-strict-equal.md)                     | Suggest using `toStrictEqual()`                                     |                  | ![suggest][] |
+| [prefer-to-be](docs/rules/prefer-to-be.md)                                   | Suggest using `toBe()` for primitive literals                       |                  | ![fixable][] |
+| [prefer-to-be-null](docs/rules/prefer-to-be-null.md)                         | Suggest using `toBeNull()`                                          | ![style][]       | ![fixable][] |
+| [prefer-to-be-undefined](docs/rules/prefer-to-be-undefined.md)               | Suggest using `toBeUndefined()`                                     | ![style][]       | ![fixable][] |
+| [prefer-to-contain](docs/rules/prefer-to-contain.md)                         | Suggest using `toContain()`                                         | ![style][]       | ![fixable][] |
+| [prefer-to-have-length](docs/rules/prefer-to-have-length.md)                 | Suggest using `toHaveLength()`                                      | ![style][]       | ![fixable][] |
+| [prefer-todo](docs/rules/prefer-todo.md)                                     | Suggest using `test.todo`                                           |                  | ![fixable][] |
+| [require-to-throw-message](docs/rules/require-to-throw-message.md)           | Require a message for `toThrow()`                                   |                  |              |
+| [require-top-level-describe](docs/rules/require-top-level-describe.md)       | Require test cases and hooks to be inside a `describe` block        |                  |              |
+| [valid-describe](docs/rules/valid-describe.md)                               | Enforce valid `describe()` callback                                 | ![recommended][] |              |
+| [valid-expect](docs/rules/valid-expect.md)                                   | Enforce valid `expect()` usage                                      | ![recommended][] |              |
+| [valid-expect-in-promise](docs/rules/valid-expect-in-promise.md)             | Enforce having return statement when testing with promises          | ![recommended][] |              |
+| [valid-title](docs/rules/valid-title.md)                                     | Enforce valid titles                                                | ![recommended][] | ![fixable][] |
 
 <!-- end base rules list -->
 
diff --git a/docs/rules/prefer-expect-resolves.md b/docs/rules/prefer-expect-resolves.md
new file mode 100644
index 0000000..baba945
--- /dev/null
+++ b/docs/rules/prefer-expect-resolves.md
@@ -0,0 +1,53 @@
+# Prefer `await expect(...).resolves` over `expect(await ...)` syntax (`prefer-expect-resolves`)
+
+When working with promises, there are two primary ways you can test the resolved
+value:
+
+1. use the `resolve` modifier on `expect`
+   (`await expect(...).resolves.<matcher>` style)
+2. `await` the promise and assert against its result
+   (`expect(await ...).<matcher>` style)
+
+While the second style is arguably less dependent on `jest`, if the promise
+rejects it will be treated as a general error, resulting in less predictable
+behaviour and output from `jest`.
+
+Additionally, favoring the first style ensures consistency with its `rejects`
+counterpart, as there is no way of "awaiting" a rejection.
+
+## Rule details
+
+This rule triggers a warning if an `await` is done within an `expect`, and
+recommends using `resolves` instead.
+
+Examples of **incorrect** code for this rule
+
+```js
+it('passes', async () => {
+  expect(await someValue()).toBe(true);
+});
+
+it('is true', async () => {
+  const myPromise = Promise.resolve(true);
+
+  expect(await myPromise).toBe(true);
+});
+```
+
+Examples of **correct** code for this rule
+
+```js
+it('passes', async () => {
+  await expect(someValue()).resolves.toBe(true);
+});
+
+it('is true', async () => {
+  const myPromise = Promise.resolve(true);
+
+  await expect(myPromise).resolves.toBe(true);
+});
+
+it('errors', async () => {
+  await expect(Promise.rejects('oh noes!')).rejects.toThrow('oh noes!');
+});
+```
diff --git a/src/rules/prefer-expect-resolves.ts b/src/rules/prefer-expect-resolves.ts
new file mode 100644
index 0000000..dd644d1
--- /dev/null
+++ b/src/rules/prefer-expect-resolves.ts
@@ -0,0 +1,49 @@
+import {
+  AST_NODE_TYPES,
+  TSESTree,
+} from '@typescript-eslint/experimental-utils';
+import { createRule, isExpectCall } from './utils';
+
+export default createRule({
+  name: __filename,
+  meta: {
+    docs: {
+      category: 'Best Practices',
+      description:
+        'Prefer `await expect(...).resolves` over `expect(await ...)` syntax',
+      recommended: false,
+    },
+    fixable: 'code',
+    messages: {
+      expectResolves: 'Use `await expect(...).resolves instead.',
+    },
+    schema: [],
+    type: 'suggestion',
+  },
+  defaultOptions: [],
+  create: context => ({
+    CallExpression(node: TSESTree.CallExpression) {
+      const [awaitNode] = node.arguments;
+
+      if (
+        isExpectCall(node) &&
+        awaitNode?.type === AST_NODE_TYPES.AwaitExpression
+      ) {
+        context.report({
+          node: node.arguments[0],
+          messageId: 'expectResolves',
+          fix(fixer) {
+            return [
+              fixer.insertTextBefore(node, 'await '),
+              fixer.removeRange([
+                awaitNode.range[0],
+                awaitNode.argument.range[0],
+              ]),
+              fixer.insertTextAfter(node, '.resolves'),
+            ];
+          },
+        });
+      }
+    },
+  }),
+});


Test patch:
diff --git a/src/__tests__/__snapshots__/rules.test.ts.snap b/src/__tests__/__snapshots__/rules.test.ts.snap
index bf6e2af..4389662 100644
--- a/src/__tests__/__snapshots__/rules.test.ts.snap
+++ b/src/__tests__/__snapshots__/rules.test.ts.snap
@@ -37,6 +37,7 @@ Object {
       "jest/no-test-return-statement": "error",
       "jest/prefer-called-with": "error",
       "jest/prefer-expect-assertions": "error",
+      "jest/prefer-expect-resolves": "error",
       "jest/prefer-hooks-on-top": "error",
       "jest/prefer-spy-on": "error",
       "jest/prefer-strict-equal": "error",
diff --git a/src/__tests__/rules.test.ts b/src/__tests__/rules.test.ts
index 88f10b1..4848873 100644
--- a/src/__tests__/rules.test.ts
+++ b/src/__tests__/rules.test.ts
@@ -2,7 +2,7 @@ import { existsSync } from 'fs';
 import { resolve } from 'path';
 import plugin from '../';
 
-const numberOfRules = 47;
+const numberOfRules = 48;
 const ruleNames = Object.keys(plugin.rules);
 const deprecatedRules = Object.entries(plugin.rules)
   .filter(([, rule]) => rule.meta.deprecated)
diff --git a/src/rules/__tests__/prefer-expect-resolves.test.ts b/src/rules/__tests__/prefer-expect-resolves.test.ts
new file mode 100644
index 0000000..0eeb1be
--- /dev/null
+++ b/src/rules/__tests__/prefer-expect-resolves.test.ts
@@ -0,0 +1,65 @@
+import { TSESLint } from '@typescript-eslint/experimental-utils';
+import dedent from 'dedent';
+import resolveFrom from 'resolve-from';
+import rule from '../prefer-expect-resolves';
+
+const ruleTester = new TSESLint.RuleTester({
+  parser: resolveFrom(require.resolve('eslint'), 'espree'),
+  parserOptions: {
+    ecmaVersion: 2017,
+  },
+});
+
+ruleTester.run('prefer-expect-resolves', rule, {
+  valid: [
+    dedent`
+      it('passes', async () => {
+        await expect(someValue()).resolves.toBe(true);
+      });
+    `,
+    dedent`
+      it('is true', async () => {
+        const myPromise = Promise.resolve(true);
+
+        await expect(myPromise).resolves.toBe(true);
+      });
+    `,
+    dedent`
+      it('errors', async () => {
+        await expect(Promise.rejects('oh noes!')).rejects.toThrow('oh noes!');
+      });
+    `,
+  ],
+  invalid: [
+    {
+      code: dedent`
+        it('passes', async () => {
+          expect(await someValue()).toBe(true);
+        });
+      `,
+      output: dedent`
+        it('passes', async () => {
+          await expect(someValue()).resolves.toBe(true);
+        });
+      `,
+      errors: [{ endColumn: 27, column: 10, messageId: 'expectResolves' }],
+    },
+    {
+      code: dedent`
+        it('is true', async () => {
+          const myPromise = Promise.resolve(true);
+
+          expect(await myPromise).toBe(true);
+        });
+      `,
+      output: dedent`
+        it('is true', async () => {
+          const myPromise = Promise.resolve(true);
+
+          await expect(myPromise).resolves.toBe(true);
+        });
+      `,
+      errors: [{ endColumn: 25, column: 10, messageId: 'expectResolves' }],
+    },
+  ],
+});