Add no-await-expression-member rule (#1586)

configs/recommended.js

@@ -22,6 +22,7 @@ module.exports = {
 		'unicorn/no-array-method-this-argument': 'error',
 		'unicorn/no-array-push-push': 'error',
 		'unicorn/no-array-reduce': 'error',
+		'unicorn/no-await-expression-member': 'error',
 		'unicorn/no-console-spaces': 'error',
 		'unicorn/no-document-cookie': 'error',
 		'unicorn/no-empty-file': 'error',

docs/rules/no-await-expression-member.md

@@ -0,0 +1,42 @@
+# Forbid member access from await expression
+
+When accessing a member from an await expression, the await expression has to be parenthesized, which is not readable.
+
+This rule is fixable for simple member access.
+
+## Fail
+
+```js
+const foo = (await import('./foo.js')).default;
+```
+
+```js
+const secondElement = (await getArray())[1];
+```
+
+```js
+const property = (await getObject()).property;
+```
+
+```js
+const data = await (await fetch('/foo')).json();
+```
+
+## Pass
+
+```js
+const {default: foo} = await import('./foo.js');
+```
+
+```js
+const [, secondElement] = await getArray();
+```
+
+```js
+const {property} = await getObject();
+```
+
+```js
+const response = await fetch('/foo');
+const data = await response.json();
+```

readme.md

@@ -55,6 +55,7 @@ Configure it in `package.json`.
 			"unicorn/no-array-method-this-argument": "error",
 			"unicorn/no-array-push-push": "error",
 			"unicorn/no-array-reduce": "error",
+			"unicorn/no-await-expression-member": "error",
 			"unicorn/no-console-spaces": "error",
 			"unicorn/no-document-cookie": "error",
 			"unicorn/no-empty-file": "error",
@@ -169,6 +170,7 @@ Each rule has emojis denoting:
 | [no-array-method-this-argument](docs/rules/no-array-method-this-argument.md) | Disallow using the `this` argument in array methods. | ✅ | 🔧 | 💡 |
 | [no-array-push-push](docs/rules/no-array-push-push.md) | Enforce combining multiple `Array#push()` into one call. | ✅ | 🔧 | 💡 |
 | [no-array-reduce](docs/rules/no-array-reduce.md) | Disallow `Array#reduce()` and `Array#reduceRight()`. | ✅ |  |  |
+| [no-await-expression-member](docs/rules/no-await-expression-member.md) | Forbid member access from await expression. | ✅ | 🔧 |  |
 | [no-console-spaces](docs/rules/no-console-spaces.md) | Do not use leading/trailing space between `console.log` parameters. | ✅ | 🔧 |  |
 | [no-document-cookie](docs/rules/no-document-cookie.md) | Do not use `document.cookie` directly. | ✅ |  |  |
 | [no-empty-file](docs/rules/no-empty-file.md) | Disallow empty files. | ✅ |  |  |

rules/fix/index.js

@@ -3,6 +3,7 @@
 module.exports = {
 	// Utilities
 	extendFixRange: require('./extend-fix-range.js'),
+	removeParentheses: require('./remove-parentheses.js'),
 
 	appendArgument: require('./append-argument.js'),
 	removeArgument: require('./remove-argument.js'),

rules/fix/remove-parentheses.js

@@ -0,0 +1,11 @@
+'use strict';
+const {getParentheses} = require('../utils/parentheses.js');
+
+function * removeParentheses(node, fixer, sourceCode) {
+	const parentheses = getParentheses(node, sourceCode);
+	for (const token of parentheses) {
+		yield fixer.remove(token);
+	}
+}
+
+module.exports = removeParentheses;

rules/no-await-expression-member.js

@@ -0,0 +1,84 @@
+'use strict';
+const {
+	removeParentheses,
+	removeMemberExpressionProperty,
+} = require('./fix/index.js');
+
+const MESSAGE_ID = 'no-await-expression-member';
+const messages = {
+	[MESSAGE_ID]: 'Do not access a member directly from an await expression.',
+};
+
+/** @param {import('eslint').Rule.RuleContext} context */
+const create = context => {
+	const sourceCode = context.getSourceCode();
+
+	return {
+		'MemberExpression[object.type="AwaitExpression"]'(memberExpression) {
+			const {property} = memberExpression;
+			const problem = {
+				node: property,
+				messageId: MESSAGE_ID,
+			};
+
+			// `const foo = (await bar)[0]`
+			if (
+				memberExpression.computed
+				&& !memberExpression.optional
+				&& property.type === 'Literal'
+				&& (property.value === 0 || property.value === 1)
+				&& memberExpression.parent.type === 'VariableDeclarator'
+				&& memberExpression.parent.init === memberExpression
+				&& memberExpression.parent.id.type === 'Identifier'
+			) {
+				problem.fix = function * (fixer) {
+					const variable = memberExpression.parent.id;
+					yield fixer.insertTextBefore(variable, property.value === 0 ? '[' : '[, ');
+					yield fixer.insertTextAfter(variable, ']');
+
+					yield removeMemberExpressionProperty(fixer, memberExpression, sourceCode);
+					yield * removeParentheses(memberExpression.object, fixer, sourceCode);
+				};
+
+				return problem;
+			}
+
+			// `const foo = (await bar).foo`
+			if (
+				!memberExpression.computed
+				&& !memberExpression.optional
+				&& property.type === 'Identifier'
+				&& memberExpression.parent.type === 'VariableDeclarator'
+				&& memberExpression.parent.init === memberExpression
+				&& memberExpression.parent.id.type === 'Identifier'
+				&& memberExpression.parent.id.name === property.name
+			) {
+				problem.fix = function * (fixer) {
+					const variable = memberExpression.parent.id;
+					yield fixer.insertTextBefore(variable, '{');
+					yield fixer.insertTextAfter(variable, '}');
+
+					yield removeMemberExpressionProperty(fixer, memberExpression, sourceCode);
+					yield * removeParentheses(memberExpression.object, fixer, sourceCode);
+				};
+
+				return problem;
+			}
+
+			return problem;
+		},
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description: 'Forbid member access from await expression.',
+		},
+		fixable: 'code',
+		schema: [],
+		messages,
+	},
+};

rules/prefer-module.js

@@ -2,10 +2,13 @@
 const {isOpeningParenToken} = require('eslint-utils');
 const isShadowed = require('./utils/is-shadowed.js');
 const isStaticRequire = require('./utils/is-static-require.js');
-const {getParentheses} = require('./utils/parentheses.js');
 const assertToken = require('./utils/assert-token.js');
 const {referenceIdentifierSelector} = require('./selectors/index.js');
-const {replaceReferenceIdentifier, removeSpacesAfter} = require('./fix/index.js');
+const {
+	removeParentheses,
+	replaceReferenceIdentifier,
+	removeSpacesAfter,
+} = require('./fix/index.js');
 
 const ERROR_USE_STRICT_DIRECTIVE = 'error/use-strict-directive';
 const ERROR_GLOBAL_RETURN = 'error/global-return';
@@ -34,15 +37,6 @@ const identifierSelector = referenceIdentifierSelector([
 	'__dirname',
 ]);
 
-function * removeParentheses(nodeOrNodes, fixer, sourceCode) {
-	for (const node of Array.isArray(nodeOrNodes) ? nodeOrNodes : [nodeOrNodes]) {
-		const parentheses = getParentheses(node, sourceCode);
-		for (const token of parentheses) {
-			yield fixer.remove(token);
-		}
-	}
-}
-
 function fixRequireCall(node, sourceCode) {
 	if (!isStaticRequire(node.parent) || node.parent.callee !== node) {
 		return;
@@ -66,7 +60,10 @@ function fixRequireCall(node, sourceCode) {
 			yield fixer.replaceText(openingParenthesisToken, ' ');
 			const closingParenthesisToken = sourceCode.getLastToken(requireCall);
 			yield fixer.remove(closingParenthesisToken);
-			yield * removeParentheses([callee, requireCall, source], fixer, sourceCode);
+
+			for (const node of [callee, requireCall, source]) {
+				yield * removeParentheses(node, fixer, sourceCode);
+			}
 		};
 	}
 
@@ -124,7 +121,9 @@ function fixRequireCall(node, sourceCode) {
 			const closingParenthesisToken = sourceCode.getLastToken(requireCall);
 			yield fixer.remove(closingParenthesisToken);
 
-			yield * removeParentheses([callee, requireCall, source], fixer, sourceCode);
+			for (const node of [callee, requireCall, source]) {
+				yield * removeParentheses(node, fixer, sourceCode);
+			}
 
 			if (id.type === 'Identifier') {
 				return;
@@ -180,7 +179,9 @@ function fixDefaultExport(node, sourceCode) {
 		yield fixer.remove(equalToken);
 		yield removeSpacesAfter(equalToken, sourceCode, fixer);
 
-		yield * removeParentheses([node.parent, node], fixer, sourceCode);
+		for (const currentNode of [node.parent, node]) {
+			yield * removeParentheses(currentNode, fixer, sourceCode);
+		}
 	};
 }
 

test/integration/test.mjs

@@ -88,7 +88,10 @@ const makeEslintTask = (project, destination) => {
 	});
 };
 
-const getBranch = mem(async dirname => (await execa('git', ['branch', '--show-current'], {cwd: dirname})).stdout);
+const getBranch = mem(async dirname => {
+	const {stdout} = await execa('git', ['branch', '--show-current'], {cwd: dirname});
+	return stdout;
+});
 
 const execute = project => {
 	const destination = project.location || path.join(dirname, 'fixtures', project.name);

test/no-await-expression-member.mjs

@@ -0,0 +1,53 @@
+import {getTester} from './utils/test.mjs';
+
+const {test} = getTester(import.meta);
+
+test.snapshot({
+	valid: [
+		'const foo = await promise',
+		'const {foo: bar} = await promise',
+		'const foo = !await promise',
+		'const foo = typeof await promise',
+		'const foo = await notPromise.method()',
+		'const foo = foo[await promise]',
+
+		// These await expression need parenthesized, but rarely used
+		'new (await promiseReturnsAClass)',
+		'(await promiseReturnsAFunction)()',
+	],
+	invalid: [
+		'(await promise)[0]',
+		'(await promise).property',
+		'const foo = (await promise).bar()',
+		'const foo = (await promise).bar?.()',
+		'const foo = (await promise)?.bar()',
+
+		'const firstElement = (await getArray())[0]',
+		'const secondElement = (await getArray())[1]',
+		'const thirdElement = (await getArray())[2]',
+		'const optionalFirstElement = (await getArray())?.[0]',
+		'const {propertyOfFirstElement} = (await getArray())[0]',
+		'const [firstElementOfFirstElement] = (await getArray())[0]',
+		'let foo, firstElement = (await getArray())[0]',
+		'var firstElement = (await getArray())[0], bar',
+
+		'const property = (await getObject()).property',
+		'const renamed = (await getObject()).property',
+		'const property = (await getObject())[property]',
+		'const property = (await getObject())?.property',
+		'const {propertyOfProperty} = (await getObject()).property',
+		'const {propertyOfProperty} = (await getObject()).propertyOfProperty',
+		'const [firstElementOfProperty] = (await getObject()).property',
+		'const [firstElementOfProperty] = (await getObject()).firstElementOfProperty',
+
+		'firstElement = (await getArray())[0]',
+		'property = (await getArray()).property',
+	],
+});
+
+test.typescript({
+	valid: [
+		'function foo () {return (await promise) as string;}',
+	],
+	invalid: [],
+});