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Merge pull request #190 from papandreou/feature/no-return-from-async
Implement no-return-from-async rule
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,44 @@ | ||
| # Disallow returning from an async test or hook (no-return-from-async) | ||
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| Mocha's tests or hooks (like `before`) may be asynchronous by returning a Promise. When such a Promise-returning function is defined using [an ES7 `async` function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function) it can be confusing when combined with an explicit `return` of a Promise, as it's mixing the two styles. | ||
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| ## Rule Details | ||
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| This rule looks for every test and hook (`before`, `after`, `beforeEach` and `afterEach`) and reports when the function is async and returns a value. Returning a non-Promise value is fine from Mocha's perspective, though it is ignored, but helps the linter catch more error cases. | ||
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| The following patterns are considered warnings: | ||
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| ```js | ||
| describe('suite', function () { | ||
| before('title', async function() { | ||
| return foo; | ||
| }); | ||
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| it('title', async function() { | ||
| return bar().then(function() { | ||
| quux(); | ||
| }); | ||
| }); | ||
| }); | ||
| ``` | ||
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| These patterns would not be considered warnings: | ||
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| ```js | ||
| describe('suite', function () { | ||
| before('title', async function() { | ||
| await foo(); | ||
| }); | ||
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| it('title', function() { | ||
| if (bailEarly) { | ||
| return; | ||
| } | ||
| await bar(); | ||
| }); | ||
| }); | ||
| ``` | ||
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| ## When Not To Use It | ||
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| * If you use another library which exposes a similar API as mocha (e.g. `before`, `after`), you should turn this rule off, because it would raise warnings. |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,51 @@ | ||
| 'use strict'; | ||
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| const astUtils = require('../util/ast'); | ||
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| function reportIfShortArrowFunction(context, node) { | ||
| if (node.body.type !== 'BlockStatement') { | ||
| context.report({ | ||
| node: node.body, | ||
| message: 'Confusing implicit return in a test with an async function' | ||
| }); | ||
| return true; | ||
| } | ||
| return false; | ||
| } | ||
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| function isAllowedReturnStatement(node) { | ||
| const argument = node.argument; | ||
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| if (astUtils.isReturnOfUndefined(node) || argument.type === 'Literal') { | ||
| return true; | ||
| } | ||
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| return false; | ||
| } | ||
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| function reportIfFunctionWithBlock(context, node) { | ||
| const returnStatement = astUtils.findReturnStatement(node.body.body); | ||
| if (returnStatement && !isAllowedReturnStatement(returnStatement)) { | ||
| context.report({ | ||
| node: returnStatement, | ||
| message: 'Unexpected use of `return` in a test with an async function' | ||
| }); | ||
| } | ||
| } | ||
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| module.exports = function (context) { | ||
| function check(node) { | ||
| if (!node.async || !astUtils.hasParentMochaFunctionCall(node)) { | ||
| return; | ||
| } | ||
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| if (!reportIfShortArrowFunction(context, node)) { | ||
| reportIfFunctionWithBlock(context, node); | ||
| } | ||
| } | ||
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| return { | ||
| FunctionExpression: check, | ||
| ArrowFunctionExpression: check | ||
| }; | ||
| }; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,135 @@ | ||
| 'use strict'; | ||
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| const RuleTester = require('eslint').RuleTester; | ||
| const rules = require('../../').rules; | ||
| const ruleTester = new RuleTester(); | ||
| const message = 'Unexpected use of `return` in a test with an async function'; | ||
| const es6parserOptions = { | ||
| sourceType: 'module', | ||
| ecmaVersion: 8 | ||
| }; | ||
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| ruleTester.run('no-return-from-async', rules['no-return-from-async'], { | ||
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| valid: [ | ||
| { | ||
| code: 'it("title", async function() {});', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { async function other() { return foo.then(function () {}); } });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { const bar = async () => { return foo.then(function () {}); }; });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { const bar = { async a() { return foo.then(function () {}); } }; });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async () => {});', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it.only("title", async function() {});', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'before("title", async function() {});', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'after("title", async function() {});', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'async function foo() { return foo.then(function () {}); }', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'var foo = async function() { return foo.then(function () {}); }', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'notMocha("title", async function() { return foo.then(function () {}); })', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| // Allowed return statements | ||
| { | ||
| code: 'it("title", async function() { return; });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { return undefined; });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { return null; });', | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { return "3"; });', | ||
| parserOptions: es6parserOptions | ||
| } | ||
| ], | ||
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| invalid: [ | ||
| { | ||
| code: 'it("title", async function() { return foo; });', | ||
| errors: [ { message, column: 32, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { return foo.then(function() {}).catch(function() {}); });', | ||
| errors: [ { message, column: 32, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async function() { var foo = bar(); return foo.then(function() {}); });', | ||
| errors: [ { message, column: 49, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async () => { return foo.then(function() {}).catch(function() {}); });', | ||
| errors: [ { message, column: 27, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it("title", async () => foo.then(function() {}));', | ||
| errors: [ { message: 'Confusing implicit return in a test with an async function', column: 25, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'it.only("title", async function() { return foo.then(function () {}); });', | ||
| errors: [ { message, column: 37, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'before("title", async function() { return foo.then(function() {}); });', | ||
| errors: [ { message, column: 36, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'beforeEach("title", async function() { return foo.then(function() {}); });', | ||
| errors: [ { message, column: 40, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'after("title", async function() { return foo.then(function() {}); });', | ||
| errors: [ { message, column: 35, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'afterEach("title", async function() { return foo.then(function() {}); });', | ||
| errors: [ { message, column: 39, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| }, | ||
| { | ||
| code: 'afterEach("title", async function() { return foo; });', | ||
| errors: [ { message, column: 39, line: 1 } ], | ||
| parserOptions: es6parserOptions | ||
| } | ||
| ] | ||
| }); |