prefer-code-point: Report cases where String.fromCharCode is not called directly (#2766)

Author: baevm

rules/prefer-code-point.js

@@ -1,4 +1,4 @@
-import {isMethodCall} from './ast/index.js';
+import {isMemberExpression, isMethodCall} from './ast/index.js';
 
 const messages = {
 	'error/charCodeAt': 'Prefer `String#codePointAt()` over `String#charCodeAt()`.',
@@ -7,47 +7,35 @@ const messages = {
 	'suggestion/fromCodePoint': 'Use `String.fromCodePoint()`.',
 };
 
-const getReplacement = node => {
-	if (isMethodCall(node, {
-		method: 'charCodeAt',
-		optionalCall: false,
-	})) {
-		return 'codePointAt';
-	}
-
-	if (isMethodCall(node, {
-		object: 'String',
-		method: 'fromCharCode',
-		optionalCall: false,
-		optionalMember: false,
-	})) {
-		return 'fromCodePoint';
-	}
-};
+const getProblem = (node, replacement) => ({
+	node,
+	messageId: `error/${node.name}`,
+	suggest: [
+		{
+			messageId: `suggestion/${replacement}`,
+			fix: fixer => fixer.replaceText(node, replacement),
+		},
+	],
+});
 
 /** @param {import('eslint').Rule.RuleContext} context */
 const create = () => ({
 	CallExpression(node) {
-		const replacement = getReplacement(node);
-
-		if (!replacement) {
-			return;
+		if (isMethodCall(node, {
+			method: 'charCodeAt',
+			optionalCall: false,
+		})) {
+			return getProblem(node.callee.property, 'codePointAt');
+		}
+	},
+	MemberExpression(node) {
+		if (isMemberExpression(node, {
+			object: 'String',
+			property: 'fromCharCode',
+			optional: false,
+		})) {
+			return getProblem(node.property, 'fromCodePoint');
 		}
-
-		const method = node.callee.property;
-		const methodName = method.name;
-		const fix = fixer => fixer.replaceText(method, replacement);
-
-		return {
-			node: method,
-			messageId: `error/${methodName}`,
-			suggest: [
-				{
-					messageId: `suggestion/${replacement}`,
-					fix,
-				},
-			],
-		};
 	},
 });
 

test/prefer-code-point.js

@@ -31,5 +31,7 @@ test.snapshot({
 		'(( (( string )).charCodeAt( ((index)), )))',
 		'String.fromCharCode( code )',
 		'(( (( String )).fromCharCode( ((code)), ) ))',
+		'String.fromCharCode.bind(String)',
+		'const x = String.fromCharCode',
 	],
 });

test/snapshots/prefer-code-point.js.md

@@ -98,3 +98,41 @@ Generated by [AVA](https://avajs.dev).
     Suggestion 1/1: Use \`String.fromCodePoint()\`.␊
       1 | (( (( String )).fromCodePoint( ((code)), ) ))␊
     `
+
+## invalid(6): String.fromCharCode.bind(String)
+
+> Input
+
+    `␊
+      1 | String.fromCharCode.bind(String)␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | String.fromCharCode.bind(String)␊
+        |        ^^^^^^^^^^^^ Prefer \`String.fromCodePoint()\` over \`String.fromCharCode()\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Use \`String.fromCodePoint()\`.␊
+      1 | String.fromCodePoint.bind(String)␊
+    `
+
+## invalid(7): const x = String.fromCharCode
+
+> Input
+
+    `␊
+      1 | const x = String.fromCharCode␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const x = String.fromCharCode␊
+        |                  ^^^^^^^^^^^^ Prefer \`String.fromCodePoint()\` over \`String.fromCharCode()\`.␊
+    ␊
+    --------------------------------------------------------------------------------␊
+    Suggestion 1/1: Use \`String.fromCodePoint()\`.␊
+      1 | const x = String.fromCodePoint␊
+    `