Add prefer-native-coercion-functions rule (#1767)

Author: fisker

configs/recommended.js

@@ -87,6 +87,7 @@ module.exports = {
 		'unicorn/prefer-modern-dom-apis': 'error',
 		'unicorn/prefer-modern-math-apis': 'error',
 		'unicorn/prefer-module': 'error',
+		'unicorn/prefer-native-coercion-functions': 'error',
 		'unicorn/prefer-negative-index': 'error',
 		'unicorn/prefer-node-protocol': 'error',
 		'unicorn/prefer-number-properties': 'error',

docs/rules/prefer-native-coercion-functions.md

@@ -0,0 +1,68 @@
+# Prefer using `String`, `Number`, `BigInt`, `Boolean`, and `Symbol` directly
+
+<!-- Do not manually modify RULE_NOTICE part. Run: `npm run generate-rule-notices` -->
+<!-- RULE_NOTICE -->
+✅ *This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config.*
+
+🔧 *This rule is [auto-fixable](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems).*
+<!-- /RULE_NOTICE -->
+
+If a function is equivalent to [`String`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String), [`Number`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number), [`BigInt`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt), [`Boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean), or [`Symbol`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol), you should use the built-in one directly. Wrapping the built-in in a function is moot.
+
+## Fail
+
+```js
+const toBoolean = value => Boolean(value);
+```
+
+```js
+function toNumber(value) {
+	return Number(value);
+}
+
+if (toNumber(foo) === 1) {}
+```
+
+```js
+const hasTruthyValue = array.some(element => element);
+```
+
+## Pass
+
+```js
+const toBoolean = Boolean;
+```
+
+```js
+if (Number(foo) === 1) {}
+```
+
+```js
+const hasTruthyValue = array.some(Boolean);
+```
+
+```js
+const toStringObject = value => new String(value);
+```
+
+```js
+const toObject= value => Object(value);
+```
+
+## Note
+
+We don't check implicit coercion like:
+
+```js
+const toString = value => '' + value;
+```
+
+```js
+const toNumber = value => +value;
+```
+
+```js
+const toBoolean = value => !!value;
+```
+
+It is recommended to enable the built-in ESLint rule [`no-implicit-coercion`](https://eslint.org/docs/rules/no-implicit-coercion) for a better experience.

readme.md

@@ -127,6 +127,7 @@ Each rule has emojis denoting:
 | [prefer-modern-dom-apis](docs/rules/prefer-modern-dom-apis.md) | Prefer `.before()` over `.insertBefore()`, `.replaceWith()` over `.replaceChild()`, prefer one of `.before()`, `.after()`, `.append()` or `.prepend()` over `insertAdjacentText()` and `insertAdjacentElement()`. | ✅ | 🔧 |  |
 | [prefer-modern-math-apis](docs/rules/prefer-modern-math-apis.md) | Prefer modern `Math` APIs over legacy patterns. | ✅ | 🔧 |  |
 | [prefer-module](docs/rules/prefer-module.md) | Prefer JavaScript modules (ESM) over CommonJS. | ✅ | 🔧 | 💡 |
+| [prefer-native-coercion-functions](docs/rules/prefer-native-coercion-functions.md) | Prefer using `String`, `Number`, `BigInt`, `Boolean`, and `Symbol` directly. | ✅ | 🔧 |  |
 | [prefer-negative-index](docs/rules/prefer-negative-index.md) | Prefer negative index over `.length - index` for `{String,Array,TypedArray}#slice()`, `Array#splice()` and `Array#at()`. | ✅ | 🔧 |  |
 | [prefer-node-protocol](docs/rules/prefer-node-protocol.md) | Prefer using the `node:` protocol when importing Node.js builtin modules. | ✅ | 🔧 |  |
 | [prefer-number-properties](docs/rules/prefer-number-properties.md) | Prefer `Number` static properties over global ones. | ✅ | 🔧 | 💡 |

rules/prefer-native-coercion-functions.js

@@ -0,0 +1,182 @@
+'use strict';
+const {getFunctionHeadLocation, getFunctionNameWithKind} = require('eslint-utils');
+const {not} = require('./selectors/index.js');
+
+const MESSAGE_ID = 'prefer-native-coercion-functions';
+const messages = {
+	[MESSAGE_ID]: '{{functionNameWithKind}} is equivalent to `{{replacementFunction}}`. Use `{{replacementFunction}}` directly.',
+};
+
+const nativeCoercionFunctionNames = new Set(['String', 'Number', 'BigInt', 'Boolean', 'Symbol']);
+const arrayMethodsWithBooleanCallback = new Set(['every', 'filter', 'find', 'findIndex', 'some']);
+
+const isNativeCoercionFunctionCall = (node, firstArgumentName) =>
+	node
+	&& node.type === 'CallExpression'
+	&& !node.optional
+	&& node.callee.type === 'Identifier'
+	&& nativeCoercionFunctionNames.has(node.callee.name)
+	&& node.arguments[0]
+	&& node.arguments[0].type === 'Identifier'
+	&& node.arguments[0].name === firstArgumentName;
+
+const isIdentityFunction = node =>
+	(
+		// `v => v`
+		node.type === 'ArrowFunctionExpression'
+		&& node.body.type === 'Identifier'
+		&& node.body.name === node.params[0].name
+	)
+	|| (
+		// `(v) => {return v;}`
+		// `function (v) {return v;}`
+		node.body.type === 'BlockStatement'
+		&& node.body.body.length === 1
+		&& node.body.body[0].type === 'ReturnStatement'
+		&& node.body.body[0].argument
+		&& node.body.body[0].argument.type === 'Identifier'
+		&& node.body.body[0].argument.name === node.params[0].name
+	);
+
+const isArrayIdentityCallback = node =>
+	isIdentityFunction(node)
+	&& node.parent.type === 'CallExpression'
+	&& !node.parent.optional
+	&& node.parent.arguments[0] === node
+	&& node.parent.callee.type === 'MemberExpression'
+	&& !node.parent.callee.computed
+	&& !node.parent.callee.optional
+	&& node.parent.callee.property.type === 'Identifier'
+	&& arrayMethodsWithBooleanCallback.has(node.parent.callee.property.name);
+
+function getCallExpression(node) {
+	const firstParameterName = node.params[0].name;
+
+	// `(v) => String(v)`
+	if (
+		node.type === 'ArrowFunctionExpression'
+		&& isNativeCoercionFunctionCall(node.body, firstParameterName)
+	) {
+		return node.body;
+	}
+
+	// `(v) => {return String(v);}`
+	// `function (v) {return String(v);}`
+	if (
+		node.body.type === 'BlockStatement'
+		&& node.body.body.length === 1
+		&& node.body.body[0].type === 'ReturnStatement'
+		&& isNativeCoercionFunctionCall(node.body.body[0].argument, firstParameterName)
+	) {
+		return node.body.body[0].argument;
+	}
+}
+
+const functionsSelector = [
+	':function',
+	'[async!=true]',
+	'[generator!=true]',
+	'[params.length>0]',
+	'[params.0.type="Identifier"]',
+	not([
+		'MethodDefinition[kind="constructor"] > .value',
+		'MethodDefinition[kind="set"] > .value',
+		'Property[kind="set"] > .value',
+	]),
+].join('');
+
+function getArrayCallbackProblem(node) {
+	if (!isArrayIdentityCallback(node)) {
+		return;
+	}
+
+	return {
+		replacementFunction: 'Boolean',
+		fix: fixer => fixer.replaceText(node, 'Boolean'),
+	};
+}
+
+function getCoercionFunctionProblem(node) {
+	const callExpression = getCallExpression(node);
+
+	if (!callExpression) {
+		return;
+	}
+
+	const {name} = callExpression.callee;
+
+	const problem = {replacementFunction: name};
+
+	if (node.type === 'FunctionDeclaration' || callExpression.arguments.length !== 1) {
+		return problem;
+	}
+
+	/** @param {import('eslint').Rule.RuleFixer} fixer */
+	problem.fix = fixer => {
+		let text = name;
+
+		if (
+			node.parent.type === 'Property'
+			&& node.parent.method
+			&& node.parent.value === node
+		) {
+			text = `: ${text}`;
+		} else if (node.parent.type === 'MethodDefinition') {
+			text = ` = ${text};`;
+		}
+
+		return fixer.replaceText(node, text);
+	};
+
+	return problem;
+}
+
+/** @param {import('eslint').Rule.RuleContext} context */
+const create = context => ({
+	[functionsSelector](node) {
+		let problem = getArrayCallbackProblem(node) || getCoercionFunctionProblem(node);
+
+		if (!problem) {
+			return;
+		}
+
+		const sourceCode = context.getSourceCode();
+		const {replacementFunction, fix} = problem;
+
+		problem = {
+			node,
+			loc: getFunctionHeadLocation(node, sourceCode),
+			messageId: MESSAGE_ID,
+			data: {
+				functionNameWithKind: getFunctionNameWithKind(node, sourceCode),
+				replacementFunction,
+			},
+		};
+
+		/*
+		We do not fix if there are:
+		- Comments: No proper place to put them.
+		- Extra parameters: Removing them may break types.
+		*/
+		if (!fix || node.params.length !== 1 || sourceCode.getCommentsInside(node).length > 0) {
+			return problem;
+		}
+
+		problem.fix = fix;
+
+		return problem;
+	},
+});
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description: 'Prefer using `String`, `Number`, `BigInt`, `Boolean`, and `Symbol` directly.',
+		},
+		fixable: 'code',
+		messages,
+	},
+};