prefer-spread: Insert semicolon if needed (#578)

Author: sindresorhus

rules/prefer-spread.js

@@ -14,7 +14,32 @@ const selector = [
 ].join('');
 
 const create = context => {
-	const getSource = node => context.getSourceCode().getText(node);
+	const sourceCode = context.getSourceCode();
+	const getSource = node => sourceCode.getText(node);
+
+	const needsSemicolon = node => {
+		const tokenBefore = sourceCode.getTokenBefore(node);
+
+		if (tokenBefore) {
+			const {type, value} = tokenBefore;
+			if (type === 'Punctuator') {
+				if (value === ';') {
+					return false;
+				}
+
+				if (value === ']' || value === ')') {
+					return true;
+				}
+			}
+
+			const lastBlockNode = sourceCode.getNodeByRangeIndex(tokenBefore.range[0]);
+			if (lastBlockNode && lastBlockNode.type === 'ObjectExpression') {
+				return true;
+			}
+		}
+
+		return false;
+	};
 
 	return {
 		[selector](node) {
@@ -23,7 +48,7 @@ const create = context => {
 				message: 'Prefer the spread operator over `Array.from()`.',
 				fix: fixer => {
 					const [arrayLikeArgument, mapFn, thisArgument] = node.arguments.map(getSource);
-					let replacement = `[...${arrayLikeArgument}]`;
+					let replacement = `${needsSemicolon(node) ? ';' : ''}[...${arrayLikeArgument}]`;
 
 					if (mapFn) {
 						const mapArguments = [mapFn, thisArgument].filter(Boolean);

test/integration/test.js

@@ -100,9 +100,7 @@ const projects = [
 	'https://github.com/sindresorhus/capture-website',
 	'https://github.com/sindresorhus/file-type',
 	'https://github.com/sindresorhus/slugify',
-	// TODO: add this project when #254 got fixed
-	// https://github.com/gatsbyjs/gatsby/blob/e720d8efe58eba0f6fae9f26ec8879128967d0b5/packages/gatsby/src/bootstrap/page-hot-reloader.js#L30
-	// 'https://github.com/gatsbyjs/gatsby',
+	'https://github.com/gatsbyjs/gatsby',
 	{
 		repository: 'https://github.com/puppeteer/puppeteer',
 		path: 'lib'

test/prefer-spread.js

@@ -123,6 +123,54 @@ ruleTester.run('prefer-spread', rule, {
 				}
 			],
 			output: '[...document.querySelectorAll("*")].map(() => {});'
+		},
+		// #254
+		{
+			code: `
+				const foo = []
+				Array.from(arrayLike).forEach(doSomething)
+			`,
+			errors: [
+				{
+					message: 'Prefer the spread operator over `Array.from()`.'
+				}
+			],
+			output: `
+				const foo = []
+				;[...arrayLike].forEach(doSomething)
+			`
+		},
+		// https://github.com/gatsbyjs/gatsby/blob/e720d8efe58eba0f6fae9f26ec8879128967d0b5/packages/gatsby/src/bootstrap/page-hot-reloader.js#L30
+		{
+			code: `
+				foo()
+				Array.from(arrayLike).forEach(doSomething)
+			`,
+			errors: [
+				{
+					message: 'Prefer the spread operator over `Array.from()`.'
+				}
+			],
+			output: `
+				foo()
+				;[...arrayLike].forEach(doSomething)
+			`
+		},
+		// https://github.com/gatsbyjs/gatsby/blob/4ab3f194cf5d6dcafcb2a75d9604aac79d963554/packages/gatsby/src/redux/__tests__/nodes.js#L277
+		{
+			code: `
+				const foo = {}
+				Array.from(arrayLike).forEach(doSomething)
+			`,
+			errors: [
+				{
+					message: 'Prefer the spread operator over `Array.from()`.'
+				}
+			],
+			output: `
+				const foo = {}
+				;[...arrayLike].forEach(doSomething)
+			`
 		}
 	]
 });