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106 lines
2.7 KiB
106 lines
2.7 KiB
/**
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* @fileoverview Rule to disallow uses of await inside of loops.
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* @author Nat Mote (nmote)
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*/
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"use strict";
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/**
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* Check whether it should stop traversing ancestors at the given node.
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* @param {ASTNode} node A node to check.
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* @returns {boolean} `true` if it should stop traversing.
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*/
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function isBoundary(node) {
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const t = node.type;
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return (
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t === "FunctionDeclaration" ||
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t === "FunctionExpression" ||
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t === "ArrowFunctionExpression" ||
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/*
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* Don't report the await expressions on for-await-of loop since it's
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* asynchronous iteration intentionally.
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*/
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(t === "ForOfStatement" && node.await === true)
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);
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}
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/**
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* Check whether the given node is in loop.
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* @param {ASTNode} node A node to check.
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* @param {ASTNode} parent A parent node to check.
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* @returns {boolean} `true` if the node is in loop.
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*/
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function isLooped(node, parent) {
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switch (parent.type) {
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case "ForStatement":
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return (
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node === parent.test ||
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node === parent.update ||
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node === parent.body
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);
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case "ForOfStatement":
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case "ForInStatement":
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return node === parent.body;
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case "WhileStatement":
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case "DoWhileStatement":
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return node === parent.test || node === parent.body;
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default:
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return false;
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}
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}
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/** @type {import('../shared/types').Rule} */
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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 `await` inside of loops",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/no-await-in-loop"
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},
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schema: [],
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messages: {
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unexpectedAwait: "Unexpected `await` inside a loop."
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}
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},
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create(context) {
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/**
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* Validate an await expression.
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* @param {ASTNode} awaitNode An AwaitExpression or ForOfStatement node to validate.
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* @returns {void}
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*/
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function validate(awaitNode) {
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if (awaitNode.type === "ForOfStatement" && !awaitNode.await) {
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return;
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}
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let node = awaitNode;
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let parent = node.parent;
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while (parent && !isBoundary(parent)) {
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if (isLooped(node, parent)) {
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context.report({
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node: awaitNode,
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messageId: "unexpectedAwait"
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});
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return;
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}
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node = parent;
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parent = parent.parent;
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}
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}
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return {
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AwaitExpression: validate,
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ForOfStatement: validate
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};
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}
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};
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