2 * @fileoverview restrict values that can be used as Promise rejection reasons
7 const astUtils = require("./utils/ast-utils");
9 //------------------------------------------------------------------------------
11 //------------------------------------------------------------------------------
18 description: "require using Error objects as Promise rejection reasons",
19 category: "Best Practices",
21 url: "https://eslint.org/docs/rules/prefer-promise-reject-errors"
30 allowEmptyReject: { type: "boolean", default: false }
32 additionalProperties: false
37 rejectAnError: "Expected the Promise rejection reason to be an Error."
43 const ALLOW_EMPTY_REJECT = context.options.length && context.options[0].allowEmptyReject;
45 //----------------------------------------------------------------------
47 //----------------------------------------------------------------------
50 * Checks the argument of a reject() or Promise.reject() CallExpression, and reports it if it can't be an Error
51 * @param {ASTNode} callExpression A CallExpression node which is used to reject a Promise
54 function checkRejectCall(callExpression) {
55 if (!callExpression.arguments.length && ALLOW_EMPTY_REJECT) {
59 !callExpression.arguments.length ||
60 !astUtils.couldBeError(callExpression.arguments[0]) ||
61 callExpression.arguments[0].type === "Identifier" && callExpression.arguments[0].name === "undefined"
65 messageId: "rejectAnError"
71 * Determines whether a function call is a Promise.reject() call
72 * @param {ASTNode} node A CallExpression node
73 * @returns {boolean} `true` if the call is a Promise.reject() call
75 function isPromiseRejectCall(node) {
76 return astUtils.isSpecificMemberAccess(node.callee, "Promise", "reject");
79 //----------------------------------------------------------------------
81 //----------------------------------------------------------------------
85 // Check `Promise.reject(value)` calls.
86 CallExpression(node) {
87 if (isPromiseRejectCall(node)) {
88 checkRejectCall(node);
93 * Check for `new Promise((resolve, reject) => {})`, and check for reject() calls.
94 * This function is run on "NewExpression:exit" instead of "NewExpression" to ensure that
95 * the nodes in the expression already have the `parent` property.
97 "NewExpression:exit"(node) {
99 node.callee.type === "Identifier" && node.callee.name === "Promise" &&
100 node.arguments.length && astUtils.isFunction(node.arguments[0]) &&
101 node.arguments[0].params.length > 1 && node.arguments[0].params[1].type === "Identifier"
103 context.getDeclaredVariables(node.arguments[0])
106 * Find the first variable that matches the second parameter's name.
107 * If the first parameter has the same name as the second parameter, then the variable will actually
108 * be "declared" when the first parameter is evaluated, but then it will be immediately overwritten
109 * by the second parameter. It's not possible for an expression with the variable to be evaluated before
110 * the variable is overwritten, because functions with duplicate parameters cannot have destructuring or
111 * default assignments in their parameter lists. Therefore, it's not necessary to explicitly account for
114 .find(variable => variable.name === node.arguments[0].params[1].name)
116 // Get the references to that variable.
119 // Only check the references that read the parameter's value.
120 .filter(ref => ref.isRead())
122 // Only check the references that are used as the callee in a function call, e.g. `reject(foo)`.
123 .filter(ref => ref.identifier.parent.type === "CallExpression" && ref.identifier === ref.identifier.parent.callee)
125 // Check the argument of the function call to determine whether it's an Error.
126 .forEach(ref => checkRejectCall(ref.identifier.parent));