eslint/lib/rules/no-promise-executor-return.js

   1 /**
   2  * @fileoverview Rule to disallow returning values from Promise executor functions
   3  * @author Milos Djermanovic
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const { findVariable } = require("@eslint-community/eslint-utils");
  13
  14 //------------------------------------------------------------------------------
  15 // Helpers
  16 //------------------------------------------------------------------------------
  17
  18 const functionTypesToCheck = new Set(["ArrowFunctionExpression", "FunctionExpression"]);
  19
  20 /**
  21  * Determines whether the given identifier node is a reference to a global variable.
  22  * @param {ASTNode} node `Identifier` node to check.
  23  * @param {Scope} scope Scope to which the node belongs.
  24  * @returns {boolean} True if the identifier is a reference to a global variable.
  25  */
  26 function isGlobalReference(node, scope) {
  27     const variable = findVariable(scope, node);
  28
  29     return variable !== null && variable.scope.type === "global" && variable.defs.length === 0;
  30 }
  31
  32 /**
  33  * Finds function's outer scope.
  34  * @param {Scope} scope Function's own scope.
  35  * @returns {Scope} Function's outer scope.
  36  */
  37 function getOuterScope(scope) {
  38     const upper = scope.upper;
  39
  40     if (upper.type === "function-expression-name") {
  41         return upper.upper;
  42     }
  43     return upper;
  44 }
  45
  46 /**
  47  * Determines whether the given function node is used as a Promise executor.
  48  * @param {ASTNode} node The node to check.
  49  * @param {Scope} scope Function's own scope.
  50  * @returns {boolean} `true` if the node is a Promise executor.
  51  */
  52 function isPromiseExecutor(node, scope) {
  53     const parent = node.parent;
  54
  55     return parent.type === "NewExpression" &&
  56         parent.arguments[0] === node &&
  57         parent.callee.type === "Identifier" &&
  58         parent.callee.name === "Promise" &&
  59         isGlobalReference(parent.callee, getOuterScope(scope));
  60 }
  61
  62 //------------------------------------------------------------------------------
  63 // Rule Definition
  64 //------------------------------------------------------------------------------
  65
  66 /** @type {import('../shared/types').Rule} */
  67 module.exports = {
  68     meta: {
  69         type: "problem",
  70
  71         docs: {
  72             description: "Disallow returning values from Promise executor functions",
  73             recommended: false,
  74             url: "https://eslint.org/docs/latest/rules/no-promise-executor-return"
  75         },
  76
  77         schema: [],
  78
  79         messages: {
  80             returnsValue: "Return values from promise executor functions cannot be read."
  81         }
  82     },
  83
  84     create(context) {
  85
  86         let funcInfo = null;
  87         const sourceCode = context.sourceCode;
  88
  89         /**
  90          * Reports the given node.
  91          * @param {ASTNode} node Node to report.
  92          * @returns {void}
  93          */
  94         function report(node) {
  95             context.report({ node, messageId: "returnsValue" });
  96         }
  97
  98         return {
  99
 100             onCodePathStart(_, node) {
 101                 funcInfo = {
 102                     upper: funcInfo,
 103                     shouldCheck: functionTypesToCheck.has(node.type) && isPromiseExecutor(node, sourceCode.getScope(node))
 104                 };
 105
 106                 if (funcInfo.shouldCheck && node.type === "ArrowFunctionExpression" && node.expression) {
 107                     report(node.body);
 108                 }
 109             },
 110
 111             onCodePathEnd() {
 112                 funcInfo = funcInfo.upper;
 113             },
 114
 115             ReturnStatement(node) {
 116                 if (funcInfo.shouldCheck && node.argument) {
 117                     report(node);
 118                 }
 119             }
 120         };
 121     }
 122 };