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- /**
- * @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("../util/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) {
- let currentNode = node;
-
- while (currentNode) {
- const parent = currentNode.parent;
-
- switch (parent.type) {
-
- /*
- * Looks up the destination. e.g.,
- * foo.every(nativeFoo || function foo() { ... });
- */
- case "LogicalExpression":
- case "ConditionalExpression":
- currentNode = 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;
- }
- currentNode = 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] === currentNode
- );
- }
- if (isTargetMethod(parent.callee)) {
- return (
- parent.arguments.length >= 1 &&
- parent.arguments[0] === currentNode
- );
- }
- return false;
-
- // Otherwise this node is not target.
- default:
- return false;
- }
- }
-
- /* istanbul ignore next: unreachable */
- return false;
- }
-
- //------------------------------------------------------------------------------
- // Rule Definition
- //------------------------------------------------------------------------------
-
- module.exports = {
- meta: {
- type: "problem",
-
- docs: {
- description: "enforce `return` statements in callbacks of array methods",
- category: "Best Practices",
- recommended: false,
- url: "https://eslint.org/docs/rules/array-callback-return"
- },
-
- schema: [
- {
- type: "object",
- properties: {
- allowImplicit: {
- type: "boolean"
- }
- },
- additionalProperties: false
- }
- ],
-
- messages: {
- expectedAtEnd: "Expected to return a value at the end of {{name}}.",
- expectedInside: "Expected to return a value in {{name}}.",
- expectedReturnValue: "{{name}} expected a return value."
- }
- },
-
- create(context) {
-
- const options = context.options[0] || { allowImplicit: false };
-
- 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,
- messageId: funcInfo.hasReturn
- ? "expectedAtEnd"
- : "expectedInside",
- 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 allowImplicit: false, should also check node.argument
- if (!options.allowImplicit && !node.argument) {
- context.report({
- node,
- messageId: "expectedReturnValue",
- data: {
- name: lodash.upperFirst(astUtils.getFunctionNameWithKind(funcInfo.node))
- }
- });
- }
- }
- },
-
- // Reports a given function if the last path is reachable.
- "FunctionExpression:exit": checkLastSegment,
- "ArrowFunctionExpression:exit": checkLastSegment
- };
- }
- };
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