prefer-array-some: Check cases comparing .find() with undefined (#1422)

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

Author: fisker

docs/rules/prefer-array-some.md

@@ -8,6 +8,8 @@ We only check `.filter().length > 0` and `.filter().length !== 0`. These two non
 
 - Using [`Array#find()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find) to ensure at least one element in the array passes a given check.
 
+- Comparing the result of [`Array#find()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find) with `undefined`.
+
 This rule is fixable for `.filter(…).length` check and has a suggestion for `.find(…)`.
 
 ## Fail
@@ -34,6 +36,14 @@ if (array.find(element => isUnicorn(element))) {
 const foo = array.find(element => isUnicorn(element)) ? bar : baz;
 ```
 
+```js
+const hasUnicorn = array.find(element => isUnicorn(element) !== undefined;
+```
+
+```js
+const hasUnicorn = array.find(element => isUnicorn(element) != null;
+```
+
 ```vue
 <template>
 	<div v-if="array.find(element => isUnicorn(element))">Vue</div>

rules/prefer-array-some.js

@@ -3,6 +3,7 @@ const {methodCallSelector, matches, memberExpressionSelector} = require('./selec
 const {checkVueTemplate} = require('./utils/rule.js');
 const {isBooleanNode} = require('./utils/boolean.js');
 const {getParenthesizedRange} = require('./utils/parentheses.js');
+const isLiteralValue = require('./utils/is-literal-value.js');
 const {removeMemberExpressionProperty} = require('./fix/index.js');
 
 const ERROR_ID_ARRAY_SOME = 'some';
@@ -20,6 +21,31 @@ const arrayFindCallSelector = methodCallSelector({
 	max: 2,
 });
 
+const isCheckingUndefined = node =>
+	node.parent.type === 'BinaryExpression' &&
+	// Not checking yoda expression `null != foo.find()` and `undefined !== foo.find()
+	node.parent.left === node &&
+	(
+		(
+			(
+				node.parent.operator === '!=' ||
+				node.parent.operator === '==' ||
+				node.parent.operator === '===' ||
+				node.parent.operator === '!=='
+			) &&
+			node.parent.right.type === 'Identifier' &&
+			node.parent.right.name === 'undefined'
+		) ||
+		(
+			(
+				node.parent.operator === '!=' ||
+				node.parent.operator === '=='
+			) &&
+			// eslint-disable-next-line unicorn/no-null
+			isLiteralValue(node.parent.right, null)
+		)
+	);
+
 const arrayFilterCallSelector = [
 	'BinaryExpression',
 	'[right.type="Literal"]',
@@ -35,7 +61,8 @@ const arrayFilterCallSelector = [
 const create = context => {
 	return {
 		[arrayFindCallSelector](findCall) {
-			if (!isBooleanNode(findCall)) {
+			const isCompare = isCheckingUndefined(findCall);
+			if (!isCompare && !isBooleanNode(findCall)) {
 				return;
 			}
 
@@ -46,7 +73,22 @@ const create = context => {
 				suggest: [
 					{
 						messageId: SUGGESTION_ID_ARRAY_SOME,
-						fix: fixer => fixer.replaceText(findProperty, 'some'),
+						* fix(fixer) {
+							yield fixer.replaceText(findProperty, 'some');
+
+							if (!isCompare) {
+								return;
+							}
+
+							const parenthesizedRange = getParenthesizedRange(findCall, context.getSourceCode());
+							yield fixer.replaceTextRange([parenthesizedRange[1], findCall.parent.range[1]], '');
+
+							if (findCall.parent.operator === '!=' || findCall.parent.operator === '!==') {
+								return;
+							}
+
+							yield fixer.insertTextBeforeRange(parenthesizedRange, '!');
+						},
 					},
 				],
 			};

test/prefer-array-some.mjs

@@ -206,3 +206,26 @@ test.vue({
 		},
 	],
 });
+
+// Compare with `undefined`
+test.snapshot({
+	valid: [
+		'foo.find(fn) == 0',
+		'foo.find(fn) != ""',
+		'foo.find(fn) === null',
+		'foo.find(fn) !== "null"',
+		'foo.find(fn) >= undefined',
+		'foo.find(fn) instanceof undefined',
+		// We are not checking this right now
+		'typeof foo.find(fn) === "undefined"',
+	],
+	invalid: [
+		'foo.find(fn) == null',
+		'foo.find(fn) == undefined',
+		'foo.find(fn) === undefined',
+		'foo.find(fn) != null',
+		'foo.find(fn) != undefined',
+		'foo.find(fn) !== undefined',
+		'a = (( ((foo.find(fn))) == ((null)) )) ? "no" : "yes";',
+	],
+});

test/snapshots/prefer-array-some.mjs.md

@@ -153,3 +153,101 @@ Generated by [AVA](https://avajs.dev).
       14 | 	))␊
       15 | );␊
     `
+
+## Invalid #1
+      1 | foo.find(fn) == null
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) == null␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | !foo.some(fn)␊
+    `
+
+## Invalid #2
+      1 | foo.find(fn) == undefined
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) == undefined␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | !foo.some(fn)␊
+    `
+
+## Invalid #3
+      1 | foo.find(fn) === undefined
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) === undefined␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | !foo.some(fn)␊
+    `
+
+## Invalid #4
+      1 | foo.find(fn) != null
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) != null␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | foo.some(fn)␊
+    `
+
+## Invalid #5
+      1 | foo.find(fn) != undefined
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) != undefined␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | foo.some(fn)␊
+    `
+
+## Invalid #6
+      1 | foo.find(fn) !== undefined
+
+> Error 1/1
+
+    `␊
+    > 1 | foo.find(fn) !== undefined␊
+        |     ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | foo.some(fn)␊
+    `
+
+## Invalid #7
+      1 | a = (( ((foo.find(fn))) == ((null)) )) ? "no" : "yes";
+
+> Error 1/1
+
+    `␊
+    > 1 | a = (( ((foo.find(fn))) == ((null)) )) ? "no" : "yes";␊
+        |              ^^^^ Prefer \`.some(…)\` over \`.find(…)\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Replace \`.find(…)\` with \`.some(…)\`.␊
+      1 | a = (( !((foo.some(fn))) )) ? "no" : "yes";␊
+    `