prefer-spread: Fix false negative on array constants (#1474)

rules/prefer-spread.js

@@ -1,6 +1,6 @@
 'use strict';
 const {isParenthesized, getStaticValue, isCommaToken, hasSideEffect} = require('eslint-utils');
-const {methodCallSelector} = require('./selectors/index.js');
+const {methodCallSelector, not} = require('./selectors/index.js');
 const needsSemicolon = require('./utils/needs-semicolon.js');
 const {getParenthesizedRange, getParenthesizedText} = require('./utils/parentheses.js');
 const shouldAddParenthesesToSpreadElementArgument = require('./utils/should-add-parentheses-to-spread-element-argument.js');
@@ -42,16 +42,12 @@ const arrayFromCallSelector = [
 
 const arrayConcatCallSelector = [
 	methodCallSelector('concat'),
-	`:not(${
+	not(
 		[
-			...[
-				'Literal',
-				'TemplateLiteral',
-			].map(type => `[callee.object.type="${type}"]`),
-			// Most likely it's a static method of a class
-			'[callee.object.name=/^[A-Z]/]',
-		].join(', ')
-	})`,
+			'Literal',
+			'TemplateLiteral',
+		].map(type => `[callee.object.type="${type}"]`),
+	),
 ].join('');
 
 const arraySliceCallSelector = [
@@ -301,6 +297,20 @@ function fixSlice(node, sourceCode) {
 	};
 }
 
+function isClassName(node) {
+	if (node.type === 'MemberExpression') {
+		node = node.property;
+	}
+
+	if (node.type !== 'Identifier') {
+		return false;
+	}
+
+	const {name} = node;
+
+	return /^[A-Z]./.test(name) && name.toUpperCase() !== name;
+}
+
 const create = context => {
 	const sourceCode = context.getSourceCode();
 
@@ -313,8 +323,14 @@ const create = context => {
 			};
 		},
 		[arrayConcatCallSelector](node) {
+			const {object} = node.callee;
+
+			if (isClassName(object)) {
+				return;
+			}
+
 			const scope = context.getScope();
-			const staticResult = getStaticValue(node.callee.object, scope);
+			const staticResult = getStaticValue(object, scope);
 
 			if (staticResult && !Array.isArray(staticResult.value)) {
 				return;

test/prefer-spread.mjs

@@ -179,8 +179,7 @@ test.snapshot({
 		'const bufA = Buffer.concat([buf1, buf2, buf3], totalLength);',
 		'Foo.concat(1)',
 		'FooBar.concat(1)',
-		'FOO.concat(1)',
-		'A.concat(1)',
+		'global.Buffer.concat([])',
 	],
 	invalid: [
 		'[1].concat(2)',
@@ -266,6 +265,10 @@ test.snapshot({
 		'foo.concat(bar, 2, 3, ...baz)',
 		'notClass.concat(1)',
 		'_A.concat(1)',
+		// Constants
+		'FOO.concat(1)',
+		'A.concat(1)',
+		'Foo.x.concat(1)',
 		// Semicolon
 		'if (test) foo.concat(1)',
 		'if (test) {} else foo.concat(1)',

test/snapshots/prefer-spread.mjs.md

@@ -1808,6 +1808,54 @@ Generated by [AVA](https://avajs.dev).
     `
 
 ## Invalid #54
+      1 | FOO.concat(1)
+
+> Output
+
+    `␊
+      1 | [...FOO, 1]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | FOO.concat(1)␊
+        |     ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
+    `
+
+## Invalid #55
+      1 | A.concat(1)
+
+> Output
+
+    `␊
+      1 | [...A, 1]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | A.concat(1)␊
+        |   ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
+    `
+
+## Invalid #56
+      1 | Foo.x.concat(1)
+
+> Output
+
+    `␊
+      1 | [...Foo.x, 1]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | Foo.x.concat(1)␊
+        |       ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
+    `
+
+## Invalid #57
       1 | if (test) foo.concat(1)
 
 > Output
@@ -1823,7 +1871,7 @@ Generated by [AVA](https://avajs.dev).
         |               ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #55
+## Invalid #58
       1 | if (test) {} else foo.concat(1)
 
 > Output
@@ -1839,7 +1887,7 @@ Generated by [AVA](https://avajs.dev).
         |                       ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #56
+## Invalid #59
       1 | if (test) {} else foo.concat(1)
 
 > Output
@@ -1855,7 +1903,7 @@ Generated by [AVA](https://avajs.dev).
         |                       ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #57
+## Invalid #60
       1 | for (;;) foo.concat(1)
 
 > Output
@@ -1871,7 +1919,7 @@ Generated by [AVA](https://avajs.dev).
         |              ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #58
+## Invalid #61
       1 | for (a in b) foo.concat(1)
 
 > Output
@@ -1887,7 +1935,7 @@ Generated by [AVA](https://avajs.dev).
         |                  ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #59
+## Invalid #62
       1 | for (a in b) foo.concat(1)
 
 > Output
@@ -1903,7 +1951,7 @@ Generated by [AVA](https://avajs.dev).
         |                  ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #60
+## Invalid #63
       1 | for (const a of b) foo.concat(1)
 
 > Output
@@ -1919,7 +1967,7 @@ Generated by [AVA](https://avajs.dev).
         |                        ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #61
+## Invalid #64
       1 | while (test) foo.concat(1)
 
 > Output
@@ -1935,7 +1983,7 @@ Generated by [AVA](https://avajs.dev).
         |                  ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #62
+## Invalid #65
       1 | do foo.concat(1); while (test)
 
 > Output
@@ -1951,7 +1999,7 @@ Generated by [AVA](https://avajs.dev).
         |        ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #63
+## Invalid #66
       1 | with (foo) foo.concat(1)
 
 > Output
@@ -1967,7 +2015,7 @@ Generated by [AVA](https://avajs.dev).
         |                ^^^^^^ Prefer the spread operator over \`Array#concat(…)\`.␊
     `
 
-## Invalid #64
+## Invalid #67
       1 | const baz = [2];
       2 | call(foo, ...[bar].concat(baz));