123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296 |
- /**
- * @fileoverview Rule to enforce return statements in callbacks of array's methods
- * @author Toru Nagashima
- */
-
- "use strict";
-
- //------------------------------------------------------------------------------
- // Requirements
- //------------------------------------------------------------------------------
-
- const astUtils = require("./utils/ast-utils");
-
- //------------------------------------------------------------------------------
- // Helpers
- //------------------------------------------------------------------------------
-
- const TARGET_NODE_TYPE = /^(?:Arrow)?FunctionExpression$/u;
- const TARGET_METHODS = /^(?:every|filter|find(?:Index)?|flatMap|forEach|map|reduce(?:Right)?|some|sort)$/u;
-
- /**
- * 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;
- }
-
- /**
- * Checks a given node is a member access which has the specified name's
- * property.
- * @param {ASTNode} node A node to check.
- * @returns {boolean} `true` if the node is a member access which has
- * the specified name's property. The node may be a `(Chain|Member)Expression` node.
- */
- function isTargetMethod(node) {
- return astUtils.isSpecificMemberAccess(node, null, TARGET_METHODS);
- }
-
- /**
- * Returns a human-legible description of an array method
- * @param {string} arrayMethodName A method name to fully qualify
- * @returns {string} the method name prefixed with `Array.` if it is a class method,
- * or else `Array.prototype.` if it is an instance method.
- */
- function fullMethodName(arrayMethodName) {
- if (["from", "of", "isArray"].includes(arrayMethodName)) {
- return "Array.".concat(arrayMethodName);
- }
- return "Array.prototype.".concat(arrayMethodName);
- }
-
- /**
- * Checks whether or not a given node is a function expression which is the
- * callback of an array method, returning the method name.
- * @param {ASTNode} node A node to check. This is one of
- * FunctionExpression or ArrowFunctionExpression.
- * @returns {string} The method name if the node is a callback method,
- * null otherwise.
- */
- function getArrayMethodName(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":
- case "ChainExpression":
- 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 null;
- }
- currentNode = func.parent;
- break;
- }
-
- /*
- * e.g.
- * Array.from([], function() {});
- * list.every(function() {});
- */
- case "CallExpression":
- if (astUtils.isArrayFromMethod(parent.callee)) {
- if (
- parent.arguments.length >= 2 &&
- parent.arguments[1] === currentNode
- ) {
- return "from";
- }
- }
- if (isTargetMethod(parent.callee)) {
- if (
- parent.arguments.length >= 1 &&
- parent.arguments[0] === currentNode
- ) {
- return astUtils.getStaticPropertyName(parent.callee);
- }
- }
- return null;
-
- // Otherwise this node is not target.
- default:
- return null;
- }
- }
-
- /* istanbul ignore next: unreachable */
- return null;
- }
-
- //------------------------------------------------------------------------------
- // 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",
- default: false
- },
- checkForEach: {
- type: "boolean",
- default: false
- }
- },
- additionalProperties: false
- }
- ],
-
- messages: {
- expectedAtEnd: "{{arrayMethodName}}() expects a value to be returned at the end of {{name}}.",
- expectedInside: "{{arrayMethodName}}() expects a return value from {{name}}.",
- expectedReturnValue: "{{arrayMethodName}}() expects a return value from {{name}}.",
- expectedNoReturnValue: "{{arrayMethodName}}() expects no useless return value from {{name}}."
- }
- },
-
- create(context) {
-
- const options = context.options[0] || { allowImplicit: false, checkForEach: false };
- const sourceCode = context.getSourceCode();
-
- let funcInfo = {
- arrayMethodName: null,
- 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) {
- return;
- }
-
- let messageId = null;
-
- if (funcInfo.arrayMethodName === "forEach") {
- if (options.checkForEach && node.type === "ArrowFunctionExpression" && node.expression) {
- messageId = "expectedNoReturnValue";
- }
- } else {
- if (node.body.type === "BlockStatement" && funcInfo.codePath.currentSegments.some(isReachable)) {
- messageId = funcInfo.hasReturn ? "expectedAtEnd" : "expectedInside";
- }
- }
-
- if (messageId) {
- const name = astUtils.getFunctionNameWithKind(node);
-
- context.report({
- node,
- loc: astUtils.getFunctionHeadLoc(node, sourceCode),
- messageId,
- data: { name, arrayMethodName: fullMethodName(funcInfo.arrayMethodName) }
- });
- }
- }
-
- return {
-
- // Stacks this function's information.
- onCodePathStart(codePath, node) {
-
- let methodName = null;
-
- if (TARGET_NODE_TYPE.test(node.type)) {
- methodName = getArrayMethodName(node);
- }
-
- funcInfo = {
- arrayMethodName: methodName,
- upper: funcInfo,
- codePath,
- hasReturn: false,
- shouldCheck:
- methodName &&
- !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) {
- return;
- }
-
- funcInfo.hasReturn = true;
-
- let messageId = null;
-
- if (funcInfo.arrayMethodName === "forEach") {
-
- // if checkForEach: true, returning a value at any path inside a forEach is not allowed
- if (options.checkForEach && node.argument) {
- messageId = "expectedNoReturnValue";
- }
- } else {
-
- // if allowImplicit: false, should also check node.argument
- if (!options.allowImplicit && !node.argument) {
- messageId = "expectedReturnValue";
- }
- }
-
- if (messageId) {
- context.report({
- node,
- messageId,
- data: {
- name: astUtils.getFunctionNameWithKind(funcInfo.node),
- arrayMethodName: fullMethodName(funcInfo.arrayMethodName)
- }
- });
- }
- },
-
- // Reports a given function if the last path is reachable.
- "FunctionExpression:exit": checkLastSegment,
- "ArrowFunctionExpression:exit": checkLastSegment
- };
- }
- };
|