prefer-string-starts-ends-with: Fix missing parentheses for some ca…

…ses (#976)

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

rules/prefer-string-starts-ends-with.js

@@ -3,6 +3,7 @@ const {isParenthesized} = require('eslint-utils');
 const getDocumentationUrl = require('./utils/get-documentation-url');
 const methodSelector = require('./utils/method-selector');
 const quoteString = require('./utils/quote-string');
+const shouldAddParenthesesToMemberExpressionObject = require('./utils/should-add-parentheses-to-member-expression-object');
 
 const MESSAGE_STARTS_WITH = 'prefer-starts-with';
 const MESSAGE_ENDS_WITH = 'prefer-ends-with';
@@ -79,7 +80,7 @@ const create = context => {
 					if (
 						// If regex is parenthesized, we can use it, so we don't need add again
 						!isParenthesized(regexNode, sourceCode) &&
-						(isParenthesized(target, sourceCode) || target.type === 'AwaitExpression')
+						(isParenthesized(target, sourceCode) || shouldAddParenthesesToMemberExpressionObject(target, sourceCode))
 					) {
 						targetString = `(${targetString})`;
 					}

rules/utils/should-add-parentheses-to-member-expression-object.js

@@ -0,0 +1,67 @@
+'use strict';
+
+const {isOpeningParenToken, isClosingParenToken} = require('eslint-utils');
+
+// Determine whether this node is a decimal integer literal.
+// Copied from https://github.com/eslint/eslint/blob/cc4871369645c3409dc56ded7a555af8a9f63d51/lib/rules/utils/ast-utils.js#L1237
+const DECIMAL_INTEGER_PATTERN = /^(?:0|0[0-7]*[89]\d*|[1-9](?:_?\d)*)$/u;
+const isDecimalInteger = node =>
+	node.type === 'Literal' &&
+	typeof node.value === 'number' &&
+	DECIMAL_INTEGER_PATTERN.test(node.raw);
+
+/**
+Determine if a constructor function is newed-up with parens.
+
+@param {Node} node - The `NewExpression` node to be checked.
+@param {SourceCode} sourceCode - The source code object.
+@returns {boolean} True if the constructor is called with parens.
+
+Copied from https://github.com/eslint/eslint/blob/cc4871369645c3409dc56ded7a555af8a9f63d51/lib/rules/no-extra-parens.js#L252
+*/
+function isNewExpressionWithParentheses(node, sourceCode) {
+	if (node.arguments.length > 0) {
+		return true;
+	}
+
+	const [penultimateToken, lastToken] = sourceCode.getLastTokens(node, 2);
+	// The expression should end with its own parens, for example, `new new Foo()` is not a new expression with parens.
+	return isOpeningParenToken(penultimateToken) &&
+		isClosingParenToken(lastToken) &&
+		node.callee.range[1] < node.range[1];
+}
+
+/**
+Check if parentheses should to be added to a `node` when it's used as an `object` of `MemberExpression`.
+
+@param {Node} node - The AST node to check.
+@param {SourceCode} sourceCode - The source code object.
+@returns {boolean}
+*/
+function shouldAddParenthesesToMemberExpressionObject(node, sourceCode) {
+	switch (node.type) {
+		// This is not a full list. Some other nodes like `FunctionDeclaration` don't need parentheses,
+		// but it's not possible to be in the place we are checking at this point.
+		case 'Identifier':
+		case 'MemberExpression':
+		case 'CallExpression':
+		case 'ChainExpression':
+		case 'TemplateLiteral':
+			return false;
+		case 'NewExpression':
+			return !isNewExpressionWithParentheses(node, sourceCode);
+		case 'Literal': {
+			/* istanbul ignore next */
+			if (isDecimalInteger(node)) {
+				return true;
+			}
+
+			return false;
+		}
+
+		default:
+			return true;
+	}
+}
+
+module.exports = shouldAddParenthesesToMemberExpressionObject;

test/prefer-string-starts-ends-with.js

@@ -133,3 +133,24 @@ test({
 		})
 	]
 });
+
+test.visualize([
+	'/^a/.test("string")',
+	'/^a/.test((0, "string"))',
+	'async function a() {return /^a/.test(await foo())}',
+	'/^a/.test(foo + bar)',
+	'/^a/.test(foo || bar)',
+	'/^a/.test(new SomeString)',
+	'/^a/.test(new (SomeString))',
+	'/^a/.test(new SomeString())',
+	'/^a/.test(new new SomeClassReturnsAStringSubClass())',
+	'/^a/.test(new SomeString(/* comment */))',
+	'/^a/.test(new SomeString("string"))',
+	'/^a/.test(foo.bar)',
+	'/^a/.test(foo.bar())',
+	'/^a/.test(foo?.bar)',
+	'/^a/.test(foo?.bar())',
+	'/^a/.test(`string`)',
+	'/^a/.test(tagged`string`)',
+	'(/^a/).test((0, "string"))'
+]);