Add no-immediate-mutation rule

docs/rules/no-immediate-mutation.md

@@ -0,0 +1,109 @@
+# Disallow immediate mutation after variable assignment
+
+💼🚫 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config). This rule is _disabled_ in the ☑️ `unopinionated` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config).
+
+🔧💡 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix) and manually fixable by [editor suggestions](https://eslint.org/docs/latest/use/core-concepts#rule-suggestions).
+
+<!-- end auto-generated rule header -->
+<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->
+
+When you create a variable and immediately mutate it, you should instead include those changes in the initial value.
+
+- Assign variable to an array literal and immediately mutate with `Array#{push,unshift}(…)`.
+- Assign variable to an object literal and immediately assign another property.
+- Assign variable to an object literal and immediately mutate with `Object.assign(…)`.
+- Assign variable to a `Set` or `WeakSet` from an array literal and immediately adding an new element with `{Set,WeakSet}.add(…)`.
+- Assign variable to a `Map` or `WeakMap` from an array literal and immediately set another key with `{Map,WeakMap}.set(…, …)`.
+
+## Examples
+
+```js
+// ❌
+const array = [1, 2];
+array.push(3, 4);
+
+// ✅
+const array = [1, 2, 3, 4];
+```
+
+```js
+// ❌
+const array = [3, 4];
+array.unshift(1, 2);
+
+// ✅
+const array = [1, 2, 3, 4];
+```
+
+```js
+// ❌
+const object = {foo: 1};
+object.bar = 2;
+
+// ✅
+const object = {foo: 1, bar: 2};
+```
+
+```js
+// ❌
+const object = {foo: 1};
+Object.assign(object, {bar: 2});
+
+// ✅
+const object = {foo: 1, bar: 2};
+```
+
+```js
+// ❌
+const object = {foo: 1};
+Object.assign(object, bar);
+
+// ✅
+const object = {foo: 1, ...bar};
+```
+
+```js
+// ❌
+const set = new Set([1, 2]);
+set.add(3);
+
+// ✅
+const set = new Set([1, 2, 3]);
+```
+
+```js
+// ❌
+const weakSet = new WeakSet([foo, bar]);
+weakSet.add(baz);
+
+// ✅
+const weakSet = new WeakSet([foo, bar, baz]);
+```
+
+```js
+// ❌
+const map = new Map([
+	['foo', 1],
+]);
+map.set('bar', 2);
+
+// ✅
+const map = new Map([
+	['foo', 1],
+	['bar', 2],
+]);
+```
+
+```js
+// ❌
+const weakMap = new WeakMap([
+	[foo, 1],
+]);
+weakMap.set(bar, 2);
+
+// ✅
+const weakMap = new WeakMap([
+	[foo, 1],
+	[bar, 2],
+]);
+```

readme.md

@@ -90,6 +90,7 @@ export default [
 | [no-empty-file](docs/rules/no-empty-file.md)                                                     | Disallow empty files.                                                                                                                                                                                             | ✅ ☑️ |    |    |
 | [no-for-loop](docs/rules/no-for-loop.md)                                                         | Do not use a `for` loop that can be replaced with a `for-of` loop.                                                                                                                                                | ✅    | 🔧 | 💡 |
 | [no-hex-escape](docs/rules/no-hex-escape.md)                                                     | Enforce the use of Unicode escapes instead of hexadecimal escapes.                                                                                                                                                | ✅ ☑️ | 🔧 |    |
+| [no-immediate-mutation](docs/rules/no-immediate-mutation.md)                                     | Disallow immediate mutation after variable assignment.                                                                                                                                                            | ✅    | 🔧 | 💡 |
 | [no-instanceof-builtins](docs/rules/no-instanceof-builtins.md)                                   | Disallow `instanceof` with built-in objects                                                                                                                                                                       | ✅ ☑️ | 🔧 | 💡 |
 | [no-invalid-fetch-options](docs/rules/no-invalid-fetch-options.md)                               | Disallow invalid options in `fetch()` and `new Request()`.                                                                                                                                                        | ✅ ☑️ |    |    |
 | [no-invalid-remove-event-listener](docs/rules/no-invalid-remove-event-listener.md)               | Prevent calling `EventTarget#removeEventListener()` with the result of an expression.                                                                                                                             | ✅ ☑️ |    |    |

rules/fix/index.js

@@ -10,13 +10,14 @@ export {
 	removeMemberExpressionProperty,
 } from './replace-member-expression-property.js';
 export {default as removeMethodCall} from './remove-method-call.js';
-export {default as replaceTemplateElement} from './replace-template-element.js';
-export {default as replaceReferenceIdentifier} from './replace-reference-identifier.js';
-export {default as renameVariable} from './rename-variable.js';
-export {default as replaceNodeOrTokenAndSpacesBefore} from './replace-node-or-token-and-spaces-before.js';
+export {default as removeExpressionStatement} from './remove-expression-statement.js';
 export {default as removeSpacesAfter} from './remove-spaces-after.js';
 export {default as removeSpecifier} from './remove-specifier.js';
 export {default as removeObjectProperty} from './remove-object-property.js';
+export {default as renameVariable} from './rename-variable.js';
+export {default as replaceTemplateElement} from './replace-template-element.js';
+export {default as replaceReferenceIdentifier} from './replace-reference-identifier.js';
+export {default as replaceNodeOrTokenAndSpacesBefore} from './replace-node-or-token-and-spaces-before.js';
 export {default as fixSpaceAroundKeyword} from './fix-space-around-keywords.js';
 export {default as replaceStringRaw} from './replace-string-raw.js';
 export {default as addParenthesizesToReturnOrThrowExpression} from './add-parenthesizes-to-return-or-throw-expression.js';

rules/fix/remove-expression-statement.js

@@ -0,0 +1,34 @@
+import {isSemicolonToken} from '@eslint-community/eslint-utils';
+const isWhitespaceOnly = text => /^\s*$/.test(text);
+
+function removeExpressionStatement(expressionStatement, context, fixer, preserveSemiColon = false) {
+	const {sourceCode} = context;
+	const {lines} = sourceCode;
+	let endToken = expressionStatement;
+
+	if (preserveSemiColon) {
+		const [penultimateToken, lastToken] = sourceCode.getLastTokens(expressionStatement, 2);
+
+		if (isSemicolonToken(lastToken)) {
+			endToken = penultimateToken;
+		}
+	}
+
+	const startLocation = sourceCode.getLoc(expressionStatement).start;
+	const endLocation = sourceCode.getLoc(endToken).end;
+
+	const textBefore = lines[startLocation.line - 1].slice(0, startLocation.column);
+	const textAfter = lines[endLocation.line - 1].slice(endLocation.column);
+
+	let [start] = sourceCode.getRange(expressionStatement);
+	let [, end] = sourceCode.getRange(endToken);
+
+	if (isWhitespaceOnly(textBefore) && isWhitespaceOnly(textAfter)) {
+		start = Math.max(0, start - textBefore.length - 1);
+		end += textAfter.length;
+	}
+
+	return fixer.removeRange([start, end]);
+}
+
+export default removeExpressionStatement;

rules/index.js

@@ -33,6 +33,7 @@ export {default as 'no-document-cookie'} from './no-document-cookie.js';
 export {default as 'no-empty-file'} from './no-empty-file.js';
 export {default as 'no-for-loop'} from './no-for-loop.js';
 export {default as 'no-hex-escape'} from './no-hex-escape.js';
+export {default as 'no-immediate-mutation'} from './no-immediate-mutation.js';
 export {default as 'no-instanceof-builtins'} from './no-instanceof-builtins.js';
 export {default as 'no-invalid-fetch-options'} from './no-invalid-fetch-options.js';
 export {default as 'no-invalid-remove-event-listener'} from './no-invalid-remove-event-listener.js';