Add prefer-event-key rule (#226)

Co-authored-by: <futpib@gmail.com>
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

docs/rules/prefer-event-key.md

@@ -0,0 +1,39 @@
+# Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`
+
+Enforces the use of [`KeyboardEvent#key`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key) over [`KeyboardEvent#keyCode`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode) which is deprecated. The `.key` property is also more semantic and readable.
+
+This rule is partly fixable. It can only fix direct property access.
+
+
+## Fail
+
+```js
+window.addEventListener('keydown', event => {
+	console.log(event.keyCode);
+});
+```
+
+```js
+window.addEventListener('keydown', event => {
+	if (event.keyCode === 8) {
+		console.log('Backspace was pressed');
+	}
+});
+```
+
+
+## Pass
+
+```js
+window.addEventListener('click', event => {
+	console.log(event.key);
+});
+```
+
+```js
+window.addEventListener('keydown', event => {
+	if (event.key === 'Backspace') {
+		console.log('Backspace was pressed');
+	}
+});
+```

index.js

@@ -39,6 +39,7 @@ module.exports = {
 				'unicorn/no-zero-fractions': 'error',
 				'unicorn/number-literal-case': 'error',
 				'unicorn/prefer-add-event-listener': 'error',
+				'unicorn/prefer-event-key': 'error',
 				'unicorn/prefer-exponentiation-operator': 'error',
 				'unicorn/prefer-flat-map': 'error',
 				'unicorn/prefer-includes': 'error',

readme.md

@@ -57,6 +57,7 @@ Configure it in `package.json`.
 			"unicorn/no-zero-fractions": "error",
 			"unicorn/number-literal-case": "error",
 			"unicorn/prefer-add-event-listener": "error",
+			"unicorn/prefer-event-key": "error",
 			"unicorn/prefer-exponentiation-operator": "error",
 			"unicorn/prefer-flat-map": "error",
 			"unicorn/prefer-includes": "error",
@@ -100,6 +101,7 @@ Configure it in `package.json`.
 - [no-zero-fractions](docs/rules/no-zero-fractions.md) - Disallow number literals with zero fractions or dangling dots. *(fixable)*
 - [number-literal-case](docs/rules/number-literal-case.md) - Enforce lowercase identifier and uppercase value for number literals. *(fixable)*
 - [prefer-add-event-listener](docs/rules/prefer-add-event-listener.md) - Prefer `.addEventListener()` and `.removeEventListener()` over `on`-functions. *(partly fixable)*
+- [prefer-event-key](docs/rules/prefer-event-key.md) - Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`. *(partly fixable)*
 - [prefer-exponentiation-operator](docs/rules/prefer-exponentiation-operator.md) - Prefer the exponentiation operator over `Math.pow()` *(fixable)*
 - [prefer-flat-map](docs/rules/prefer-flat-map.md) - Prefer `.flatMap(…)` over `.map(…).flat()`. *(fixable)*
 - [prefer-includes](docs/rules/prefer-includes.md) - Prefer `.includes()` over `.indexOf()` when checking for existence or non-existence. *(fixable)*

rules/prefer-event-key.js

@@ -0,0 +1,225 @@
+'use strict';
+const getDocsUrl = require('./utils/get-docs-url');
+
+const keys = [
+	'keyCode',
+	'charCode',
+	'which'
+];
+
+// https://github.com/facebook/react/blob/b87aabd/packages/react-dom/src/events/getEventKey.js#L36
+// Only meta characters which can't be deciphered from `String.fromCharCode()`
+const translateToKey = {
+	8: 'Backspace',
+	9: 'Tab',
+	12: 'Clear',
+	13: 'Enter',
+	16: 'Shift',
+	17: 'Control',
+	18: 'Alt',
+	19: 'Pause',
+	20: 'CapsLock',
+	27: 'Escape',
+	32: ' ',
+	33: 'PageUp',
+	34: 'PageDown',
+	35: 'End',
+	36: 'Home',
+	37: 'ArrowLeft',
+	38: 'ArrowUp',
+	39: 'ArrowRight',
+	40: 'ArrowDown',
+	45: 'Insert',
+	46: 'Delete',
+	112: 'F1',
+	113: 'F2',
+	114: 'F3',
+	115: 'F4',
+	116: 'F5',
+	117: 'F6',
+	118: 'F7',
+	119: 'F8',
+	120: 'F9',
+	121: 'F10',
+	122: 'F11',
+	123: 'F12',
+	144: 'NumLock',
+	145: 'ScrollLock',
+	186: ';',
+	187: '=',
+	188: ',',
+	189: '-',
+	190: '.',
+	191: '/',
+	219: '[',
+	220: '\\',
+	221: ']',
+	222: '\'',
+	224: 'Meta'
+};
+
+const isPropertyNamedAddEventListener = node =>
+	node &&
+	node.type === 'CallExpression' &&
+	node.callee &&
+	node.callee.type === 'MemberExpression' &&
+	node.callee.property &&
+	node.callee.property.name === 'addEventListener';
+
+const getEventNodeAndReferences = (context, node) => {
+	const eventListener = getMatchingAncestorOfType(node, 'CallExpression', isPropertyNamedAddEventListener);
+	const callback = eventListener && eventListener.arguments && eventListener.arguments[1];
+	switch (callback && callback.type) {
+		case 'ArrowFunctionExpression':
+		case 'FunctionExpression': {
+			const eventVariable = context.getDeclaredVariables(callback)[0];
+			const references = eventVariable && eventVariable.references;
+			return {
+				event: callback.params && callback.params[0],
+				references
+			};
+		}
+
+		default:
+			return {};
+	}
+};
+
+const isPropertyOf = (node, eventNode) => {
+	return (
+		node &&
+		node.parent &&
+		node.parent.type === 'MemberExpression' &&
+		node.parent.object &&
+		node.parent.object === eventNode
+	);
+};
+
+// The third argument is a condition function, as one passed to `Array#filter()`
+// Helpful if nearest node of type also needs to have some other property
+const getMatchingAncestorOfType = (node, type, fn = n => n || true) => {
+	let current = node;
+	while (current) {
+		if (current.type === type && fn(current)) {
+			return current;
+		}
+
+		current = current.parent;
+	}
+
+	return null;
+};
+
+const getParentByLevel = (node, level) => {
+	let current = node;
+	while (current && level) {
+		level--;
+		current = current.parent;
+	}
+
+	if (level === 0) {
+		return current;
+	}
+};
+
+const fix = node => fixer => {
+	// Since we're only fixing direct property access usages, like `event.keyCode`
+	const nearestIf = getParentByLevel(node, 3);
+	if (!nearestIf || nearestIf.type !== 'IfStatement') {
+		return;
+	}
+
+	const {right = {}, operator} = nearestIf.test;
+	const isTestingEquality = operator === '==' || operator === '===';
+	const isRightValid = isTestingEquality && right.type === 'Literal' && typeof right.value === 'number';
+	// Either a meta key or a printable character
+	const keyCode = translateToKey[right.value] || String.fromCharCode(right.value);
+	// And if we recognize the `.keyCode`
+	if (!isRightValid || !keyCode) {
+		return;
+	}
+
+	// Apply fixes
+	return [
+		fixer.replaceText(node, 'key'),
+		fixer.replaceText(right, `'${keyCode}'`)
+	];
+};
+
+const create = context => {
+	const report = node => {
+		context.report({
+			message: `Use \`.key\` instead of \`.${node.name}\``,
+			node,
+			fix: fix(node)
+		});
+	};
+
+	return {
+		'Identifier:matches([name=keyCode], [name=charCode], [name=which])'(node) {
+			// Normal case when usage is direct -> `event.keyCode`
+			const {event, references} = getEventNodeAndReferences(context, node);
+			if (!event) {
+				return;
+			}
+
+			const isPropertyOfEvent = Boolean(references && references.find(r => isPropertyOf(node, r.identifier)));
+			if (isPropertyOfEvent) {
+				report(node);
+			}
+		},
+
+		Property(node) {
+			// Destructured case
+			const propertyName = node.value && node.value.name;
+			if (!keys.includes(propertyName)) {
+				return;
+			}
+
+			const {event, references} = getEventNodeAndReferences(context, node);
+			if (!event) {
+				return;
+			}
+
+			const nearestVariableDeclarator = getMatchingAncestorOfType(
+				node,
+				'VariableDeclarator'
+			);
+			const initObject =
+				nearestVariableDeclarator &&
+				nearestVariableDeclarator.init &&
+				nearestVariableDeclarator.init;
+
+			// Make sure initObject is a reference of eventVariable
+			const isReferenceOfEvent = Boolean(
+				references && references.find(r => r.identifier === initObject)
+			);
+			if (isReferenceOfEvent) {
+				report(node.value);
+				return;
+			}
+
+			// When the event parameter itself is destructured directly
+			const isEventParamDestructured = event.type === 'ObjectPattern';
+			if (isEventParamDestructured) {
+				// Check for properties
+				for (const prop of event.properties) {
+					if (prop === node) {
+						report(node.value);
+					}
+				}
+			}
+		}
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			url: getDocsUrl(__filename)
+		},
+		fixable: 'code'
+	}
+};