no-useless-spread: Safely remove empty array and object (#2764)

Co-authored-by: fisker <[email protected]>

Author: voderl

rules/no-useless-spread.js

@@ -176,6 +176,18 @@ const create = context => {
 					yield fixer.remove(penultimateToken);
 				}
 
+				// `[...[], 1]`
+				//        ^
+				if (
+					(node.type === 'ArrayExpression' && node.elements.length === 0)
+					|| (node.type === 'ObjectExpression' && node.properties.length === 0)
+				) {
+					const nextToken = sourceCode.getTokenAfter(spreadElement);
+					if (isCommaToken(nextToken)) {
+						yield fixer.remove(nextToken);
+					}
+				}
+
 				if (parentType !== 'CallExpression' && parentType !== 'NewExpression') {
 					return;
 				}

test/no-useless-spread.js

@@ -77,6 +77,11 @@ test.snapshot({
 		'const object = {a, ...{a, b}, b,}',
 		'foo(a, ...[a, b], b,)',
 		'new Foo(a, ...[a, b], b,)',
+		'const array = [a, ...[], b]',
+		'const array = [a, ...(( [] )),]',
+		'const array = [a, ...(( [] ))]',
+		'const array = [a, ...[b], c]',
+		'const object = {a, ...(({})), b,}',
 
 		// Duplicated keys
 		'({a:1, ...{a: 2}})',

test/snapshots/no-useless-spread.js.md

@@ -949,7 +949,112 @@ Generated by [AVA](https://avajs.dev).
         |            ^^^ Spread an array literal in arguments is unnecessary.␊
     `
 
-## invalid(46): ({a:1, ...{a: 2}})
+## invalid(46): const array = [a, ...[], b]
+
+> Input
+
+    `␊
+      1 | const array = [a, ...[], b]␊
+    `
+
+> Output
+
+    `␊
+      1 | const array = [a,  b]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const array = [a, ...[], b]␊
+        |                   ^^^ Spread an array literal in array literal is unnecessary.␊
+    `
+
+## invalid(47): const array = [a, ...(( [] )),]
+
+> Input
+
+    `␊
+      1 | const array = [a, ...(( [] )),]␊
+    `
+
+> Output
+
+    `␊
+      1 | const array = [a,   ]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const array = [a, ...(( [] )),]␊
+        |                   ^^^ Spread an array literal in array literal is unnecessary.␊
+    `
+
+## invalid(48): const array = [a, ...(( [] ))]
+
+> Input
+
+    `␊
+      1 | const array = [a, ...(( [] ))]␊
+    `
+
+> Output
+
+    `␊
+      1 | const array = [a,   ]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const array = [a, ...(( [] ))]␊
+        |                   ^^^ Spread an array literal in array literal is unnecessary.␊
+    `
+
+## invalid(49): const array = [a, ...[b], c]
+
+> Input
+
+    `␊
+      1 | const array = [a, ...[b], c]␊
+    `
+
+> Output
+
+    `␊
+      1 | const array = [a, b, c]␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const array = [a, ...[b], c]␊
+        |                   ^^^ Spread an array literal in array literal is unnecessary.␊
+    `
+
+## invalid(50): const object = {a, ...(({})), b,}
+
+> Input
+
+    `␊
+      1 | const object = {a, ...(({})), b,}␊
+    `
+
+> Output
+
+    `␊
+      1 | const object = {a,  b,}␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | const object = {a, ...(({})), b,}␊
+        |                    ^^^ Spread an object literal in object literal is unnecessary.␊
+    `
+
+## invalid(51): ({a:1, ...{a: 2}})
 
 > Input
 
@@ -970,7 +1075,7 @@ Generated by [AVA](https://avajs.dev).
         |        ^^^ Spread an object literal in object literal is unnecessary.␊
     `
 
-## invalid(47): ({...{a:1}, ...{a: 2}})
+## invalid(52): ({...{a:1}, ...{a: 2}})
 
 > Input
 
@@ -998,7 +1103,7 @@ Generated by [AVA](https://avajs.dev).
         |             ^^^ Spread an object literal in object literal is unnecessary.␊
     `
 
-## invalid(48): ({ get a() {}, set a(v) {}, ...{ get a() {} } })
+## invalid(53): ({ get a() {}, set a(v) {}, ...{ get a() {} } })
 
 > Input
 
@@ -1037,7 +1142,7 @@ Generated by [AVA](https://avajs.dev).
       7 | })␊
     `
 
-## invalid(49): ({[a]:1, ...{[a]: 2}})
+## invalid(54): ({[a]:1, ...{[a]: 2}})
 
 > Input
 
@@ -1058,7 +1163,7 @@ Generated by [AVA](https://avajs.dev).
         |          ^^^ Spread an object literal in object literal is unnecessary.␊
     `
 
-## invalid(50): const object = { a: 1, ...{ testKeys() { console.assert(Object.keys(this).length === 2) } } } object.testKeys();
+## invalid(55): const object = { a: 1, ...{ testKeys() { console.assert(Object.keys(this).length === 2) } } } object.testKeys();
 
 > Input
 
@@ -1106,7 +1211,7 @@ Generated by [AVA](https://avajs.dev).
       10 | object.testKeys();␊
     `
 
-## invalid(51): new Foo( foo( a, ...[a, b], b, ), ...[ a, ...[ a, b, ], b, ], { a: [...[a, b]], ...{ a, b, }, } )
+## invalid(56): new Foo( foo( a, ...[a, b], b, ), ...[ a, ...[ a, b, ], b, ], { a: [...[a, b]], ...{ a, b, }, } )
 
 > Input
 
@@ -1302,7 +1407,7 @@ Generated by [AVA](https://avajs.dev).
       22 | )␊
     `
 
-## invalid(52): const baz = [2]; call(foo, ...[bar, ...baz]);
+## invalid(57): const baz = [2]; call(foo, ...[bar, ...baz]);
 
 > Input
 
@@ -1326,7 +1431,7 @@ Generated by [AVA](https://avajs.dev).
         |           ^^^ Spread an array literal in arguments is unnecessary.␊
     `
 
-## invalid(53): Promise.all(...[...iterable])
+## invalid(58): Promise.all(...[...iterable])
 
 > Input
 
@@ -1347,7 +1452,7 @@ Generated by [AVA](https://avajs.dev).
         |             ^^^ Spread an array literal in arguments is unnecessary.␊
     `
 
-## invalid(54): new Map(...[...iterable])
+## invalid(59): new Map(...[...iterable])
 
 > Input