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- /**
- * @fileoverview restrict values that can be used as Promise rejection reasons
- * @author Teddy Katz
- */
- "use strict";
- const astUtils = require("./utils/ast-utils");
- //------------------------------------------------------------------------------
- // Rule Definition
- //------------------------------------------------------------------------------
- /** @type {import('../types').Rule.RuleModule} */
- module.exports = {
- meta: {
- type: "suggestion",
- defaultOptions: [
- {
- allowEmptyReject: false,
- },
- ],
- docs: {
- description:
- "Require using Error objects as Promise rejection reasons",
- recommended: false,
- url: "https://eslint.org/docs/latest/rules/prefer-promise-reject-errors",
- },
- fixable: null,
- schema: [
- {
- type: "object",
- properties: {
- allowEmptyReject: { type: "boolean" },
- },
- additionalProperties: false,
- },
- ],
- messages: {
- rejectAnError:
- "Expected the Promise rejection reason to be an Error.",
- },
- },
- create(context) {
- const [{ allowEmptyReject }] = context.options;
- const sourceCode = context.sourceCode;
- //----------------------------------------------------------------------
- // Helpers
- //----------------------------------------------------------------------
- /**
- * Checks the argument of a reject() or Promise.reject() CallExpression, and reports it if it can't be an Error
- * @param {ASTNode} callExpression A CallExpression node which is used to reject a Promise
- * @returns {void}
- */
- function checkRejectCall(callExpression) {
- if (!callExpression.arguments.length && allowEmptyReject) {
- return;
- }
- if (
- !callExpression.arguments.length ||
- !astUtils.couldBeError(callExpression.arguments[0]) ||
- (callExpression.arguments[0].type === "Identifier" &&
- callExpression.arguments[0].name === "undefined")
- ) {
- context.report({
- node: callExpression,
- messageId: "rejectAnError",
- });
- }
- }
- /**
- * Determines whether a function call is a Promise.reject() call
- * @param {ASTNode} node A CallExpression node
- * @returns {boolean} `true` if the call is a Promise.reject() call
- */
- function isPromiseRejectCall(node) {
- return astUtils.isSpecificMemberAccess(
- node.callee,
- "Promise",
- "reject",
- );
- }
- //----------------------------------------------------------------------
- // Public
- //----------------------------------------------------------------------
- return {
- // Check `Promise.reject(value)` calls.
- CallExpression(node) {
- if (isPromiseRejectCall(node)) {
- checkRejectCall(node);
- }
- },
- /*
- * Check for `new Promise((resolve, reject) => {})`, and check for reject() calls.
- * This function is run on "NewExpression:exit" instead of "NewExpression" to ensure that
- * the nodes in the expression already have the `parent` property.
- */
- "NewExpression:exit"(node) {
- if (
- node.callee.type === "Identifier" &&
- node.callee.name === "Promise" &&
- node.arguments.length &&
- astUtils.isFunction(node.arguments[0]) &&
- node.arguments[0].params.length > 1 &&
- node.arguments[0].params[1].type === "Identifier"
- ) {
- sourceCode
- .getDeclaredVariables(node.arguments[0])
- /*
- * Find the first variable that matches the second parameter's name.
- * If the first parameter has the same name as the second parameter, then the variable will actually
- * be "declared" when the first parameter is evaluated, but then it will be immediately overwritten
- * by the second parameter. It's not possible for an expression with the variable to be evaluated before
- * the variable is overwritten, because functions with duplicate parameters cannot have destructuring or
- * default assignments in their parameter lists. Therefore, it's not necessary to explicitly account for
- * this case.
- */
- .find(
- variable =>
- variable.name ===
- node.arguments[0].params[1].name,
- )
- // Get the references to that variable.
- .references // Only check the references that read the parameter's value.
- .filter(ref => ref.isRead())
- // Only check the references that are used as the callee in a function call, e.g. `reject(foo)`.
- .filter(
- ref =>
- ref.identifier.parent.type ===
- "CallExpression" &&
- ref.identifier === ref.identifier.parent.callee,
- )
- // Check the argument of the function call to determine whether it's an Error.
- .forEach(ref => checkRejectCall(ref.identifier.parent));
- }
- },
- };
- },
- };
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