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feat: create
prefer-expect-resolves rule (#822)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,53 @@ | ||
| # Prefer `await expect(...).resolves` over `expect(await ...)` syntax (`prefer-expect-resolves`) | ||
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| When working with promises, there are two primary ways you can test the resolved | ||
| value: | ||
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| 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) | ||
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| 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`. | ||
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| Additionally, favoring the first style ensures consistency with its `rejects` | ||
| counterpart, as there is no way of "awaiting" a rejection. | ||
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| ## Rule details | ||
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| This rule triggers a warning if an `await` is done within an `expect`, and | ||
| recommends using `resolves` instead. | ||
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| Examples of **incorrect** code for this rule | ||
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| ```js | ||
| it('passes', async () => { | ||
| expect(await someValue()).toBe(true); | ||
| }); | ||
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| it('is true', async () => { | ||
| const myPromise = Promise.resolve(true); | ||
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| expect(await myPromise).toBe(true); | ||
| }); | ||
| ``` | ||
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| Examples of **correct** code for this rule | ||
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| ```js | ||
| it('passes', async () => { | ||
| await expect(someValue()).resolves.toBe(true); | ||
| }); | ||
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| it('is true', async () => { | ||
| const myPromise = Promise.resolve(true); | ||
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| await expect(myPromise).resolves.toBe(true); | ||
| }); | ||
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| it('errors', async () => { | ||
| await expect(Promise.rejects('oh noes!')).rejects.toThrow('oh noes!'); | ||
| }); | ||
| ``` |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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'; | ||
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| const ruleTester = new TSESLint.RuleTester({ | ||
| parser: resolveFrom(require.resolve('eslint'), 'espree'), | ||
| parserOptions: { | ||
| ecmaVersion: 2017, | ||
| }, | ||
| }); | ||
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| 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' }], | ||
| }, | ||
| ], | ||
| }); |
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