/**
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* @fileoverview Rule to disallow returning values from Promise executor functions
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* @author Milos Djermanovic
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const { findVariable } = require("eslint-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const functionTypesToCheck = new Set(["ArrowFunctionExpression", "FunctionExpression"]);
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/**
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* Determines whether the given identifier node is a reference to a global variable.
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* @param {ASTNode} node `Identifier` node to check.
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* @param {Scope} scope Scope to which the node belongs.
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* @returns {boolean} True if the identifier is a reference to a global variable.
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*/
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function isGlobalReference(node, scope) {
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const variable = findVariable(scope, node);
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return variable !== null && variable.scope.type === "global" && variable.defs.length === 0;
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}
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/**
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* Finds function's outer scope.
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* @param {Scope} scope Function's own scope.
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* @returns {Scope} Function's outer scope.
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*/
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function getOuterScope(scope) {
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const upper = scope.upper;
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if (upper.type === "function-expression-name") {
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return upper.upper;
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}
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return upper;
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}
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/**
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* Determines whether the given function node is used as a Promise executor.
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* @param {ASTNode} node The node to check.
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* @param {Scope} scope Function's own scope.
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* @returns {boolean} `true` if the node is a Promise executor.
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*/
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function isPromiseExecutor(node, scope) {
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const parent = node.parent;
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return parent.type === "NewExpression" &&
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parent.arguments[0] === node &&
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parent.callee.type === "Identifier" &&
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parent.callee.name === "Promise" &&
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isGlobalReference(parent.callee, getOuterScope(scope));
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "problem",
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docs: {
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description: "disallow returning values from Promise executor functions",
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category: "Possible Errors",
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recommended: false,
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url: "https://eslint.org/docs/rules/no-promise-executor-return"
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},
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schema: [],
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messages: {
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returnsValue: "Return values from promise executor functions cannot be read."
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}
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},
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create(context) {
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let funcInfo = null;
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/**
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* Reports the given node.
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* @param {ASTNode} node Node to report.
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* @returns {void}
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*/
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function report(node) {
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context.report({ node, messageId: "returnsValue" });
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}
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return {
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onCodePathStart(_, node) {
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funcInfo = {
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upper: funcInfo,
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shouldCheck: functionTypesToCheck.has(node.type) && isPromiseExecutor(node, context.getScope())
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};
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if (funcInfo.shouldCheck && node.type === "ArrowFunctionExpression" && node.expression) {
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report(node.body);
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}
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},
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onCodePathEnd() {
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funcInfo = funcInfo.upper;
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},
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ReturnStatement(node) {
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if (funcInfo.shouldCheck && node.argument) {
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report(node);
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}
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}
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};
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}
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};
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