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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/array-callback-return.js')
| -rw-r--r-- | tools/node_modules/eslint/lib/rules/array-callback-return.js | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/array-callback-return.js b/tools/node_modules/eslint/lib/rules/array-callback-return.js new file mode 100644 index 0000000000..37d6ebe3a7 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/array-callback-return.js @@ -0,0 +1,232 @@ +/** + * @fileoverview Rule to enforce return statements in callbacks of array's methods + * @author Toru Nagashima + */ + +"use strict"; + +//------------------------------------------------------------------------------ +// Requirements +//------------------------------------------------------------------------------ + +const lodash = require("lodash"); + +const astUtils = require("../ast-utils"); + +//------------------------------------------------------------------------------ +// Helpers +//------------------------------------------------------------------------------ + +const TARGET_NODE_TYPE = /^(?:Arrow)?FunctionExpression$/; +const TARGET_METHODS = /^(?:every|filter|find(?:Index)?|map|reduce(?:Right)?|some|sort)$/; + +/** + * Checks a given code path segment is reachable. + * + * @param {CodePathSegment} segment - A segment to check. + * @returns {boolean} `true` if the segment is reachable. + */ +function isReachable(segment) { + return segment.reachable; +} + +/** + * Gets a readable location. + * + * - FunctionExpression -> the function name or `function` keyword. + * - ArrowFunctionExpression -> `=>` token. + * + * @param {ASTNode} node - A function node to get. + * @param {SourceCode} sourceCode - A source code to get tokens. + * @returns {ASTNode|Token} The node or the token of a location. + */ +function getLocation(node, sourceCode) { + if (node.type === "ArrowFunctionExpression") { + return sourceCode.getTokenBefore(node.body); + } + return node.id || node; +} + +/** + * Checks a given node is a MemberExpression node which has the specified name's + * property. + * + * @param {ASTNode} node - A node to check. + * @returns {boolean} `true` if the node is a MemberExpression node which has + * the specified name's property + */ +function isTargetMethod(node) { + return ( + node.type === "MemberExpression" && + TARGET_METHODS.test(astUtils.getStaticPropertyName(node) || "") + ); +} + +/** + * Checks whether or not a given node is a function expression which is the + * callback of an array method. + * + * @param {ASTNode} node - A node to check. This is one of + * FunctionExpression or ArrowFunctionExpression. + * @returns {boolean} `true` if the node is the callback of an array method. + */ +function isCallbackOfArrayMethod(node) { + while (node) { + const parent = node.parent; + + switch (parent.type) { + + /* + * Looks up the destination. e.g., + * foo.every(nativeFoo || function foo() { ... }); + */ + case "LogicalExpression": + case "ConditionalExpression": + node = parent; + break; + + /* + * If the upper function is IIFE, checks the destination of the return value. + * e.g. + * foo.every((function() { + * // setup... + * return function callback() { ... }; + * })()); + */ + case "ReturnStatement": { + const func = astUtils.getUpperFunction(parent); + + if (func === null || !astUtils.isCallee(func)) { + return false; + } + node = func.parent; + break; + } + + /* + * e.g. + * Array.from([], function() {}); + * list.every(function() {}); + */ + case "CallExpression": + if (astUtils.isArrayFromMethod(parent.callee)) { + return ( + parent.arguments.length >= 2 && + parent.arguments[1] === node + ); + } + if (isTargetMethod(parent.callee)) { + return ( + parent.arguments.length >= 1 && + parent.arguments[0] === node + ); + } + return false; + + // Otherwise this node is not target. + default: + return false; + } + } + + /* istanbul ignore next: unreachable */ + return false; +} + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "enforce `return` statements in callbacks of array methods", + category: "Best Practices", + recommended: false + }, + + schema: [] + }, + + create(context) { + let funcInfo = { + upper: null, + codePath: null, + hasReturn: false, + shouldCheck: false, + node: null + }; + + /** + * Checks whether or not the last code path segment is reachable. + * Then reports this function if the segment is reachable. + * + * If the last code path segment is reachable, there are paths which are not + * returned or thrown. + * + * @param {ASTNode} node - A node to check. + * @returns {void} + */ + function checkLastSegment(node) { + if (funcInfo.shouldCheck && + funcInfo.codePath.currentSegments.some(isReachable) + ) { + context.report({ + node, + loc: getLocation(node, context.getSourceCode()).loc.start, + message: funcInfo.hasReturn + ? "Expected to return a value at the end of {{name}}." + : "Expected to return a value in {{name}}.", + data: { + name: astUtils.getFunctionNameWithKind(funcInfo.node) + } + }); + } + } + + return { + + // Stacks this function's information. + onCodePathStart(codePath, node) { + funcInfo = { + upper: funcInfo, + codePath, + hasReturn: false, + shouldCheck: + TARGET_NODE_TYPE.test(node.type) && + node.body.type === "BlockStatement" && + isCallbackOfArrayMethod(node) && + !node.async && + !node.generator, + node + }; + }, + + // Pops this function's information. + onCodePathEnd() { + funcInfo = funcInfo.upper; + }, + + // Checks the return statement is valid. + ReturnStatement(node) { + if (funcInfo.shouldCheck) { + funcInfo.hasReturn = true; + + if (!node.argument) { + context.report({ + node, + message: "{{name}} expected a return value.", + data: { + name: lodash.upperFirst(astUtils.getFunctionNameWithKind(funcInfo.node)) + } + }); + } + } + }, + + // Reports a given function if the last path is reachable. + "FunctionExpression:exit": checkLastSegment, + "ArrowFunctionExpression:exit": checkLastSegment + }; + } +}; |