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-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 module.exports = {
  67     meta: {
  68         type: "problem",
  69
  70         docs: {
  71             description: "disallow returning values from Promise executor functions",
  72             category: "Possible Errors",
  73             recommended: false,
  74             url: "https://eslint.org/docs/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
  88         /**
  89          * Reports the given node.
  90          * @param {ASTNode} node Node to report.
  91          * @returns {void}
  92          */
  93         function report(node) {
  94             context.report({ node, messageId: "returnsValue" });
  95         }
  96
  97         return {
  98
  99             onCodePathStart(_, node) {
 100                 funcInfo = {
 101                     upper: funcInfo,
 102                     shouldCheck: functionTypesToCheck.has(node.type) && isPromiseExecutor(node, context.getScope())
 103                 };
 104
 105                 if (funcInfo.shouldCheck && node.type === "ArrowFunctionExpression" && node.expression) {
 106                     report(node.body);
 107                 }
 108             },
 109
 110             onCodePathEnd() {
 111                 funcInfo = funcInfo.upper;
 112             },
 113
 114             ReturnStatement(node) {
 115                 if (funcInfo.shouldCheck && node.argument) {
 116                     report(node);
 117                 }
 118             }
 119         };
 120     }
 121 };