/**
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* @fileoverview Traverser to traverse AST trees.
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* @author Nicholas C. Zakas
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* @author Toru Nagashima
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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 vk = require("eslint-visitor-keys");
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const debug = require("debug")("eslint:traverser");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Do nothing.
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* @returns {void}
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*/
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function noop() {
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// do nothing.
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}
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/**
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* Check whether the given value is an ASTNode or not.
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* @param {any} x The value to check.
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* @returns {boolean} `true` if the value is an ASTNode.
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*/
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function isNode(x) {
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return x !== null && typeof x === "object" && typeof x.type === "string";
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}
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/**
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* Get the visitor keys of a given node.
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* @param {Object} visitorKeys The map of visitor keys.
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* @param {ASTNode} node The node to get their visitor keys.
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* @returns {string[]} The visitor keys of the node.
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*/
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function getVisitorKeys(visitorKeys, node) {
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let keys = visitorKeys[node.type];
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if (!keys) {
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keys = vk.getKeys(node);
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debug("Unknown node type \"%s\": Estimated visitor keys %j", node.type, keys);
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}
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return keys;
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}
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/**
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* The traverser class to traverse AST trees.
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*/
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class Traverser {
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constructor() {
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this._current = null;
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this._parents = [];
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this._skipped = false;
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this._broken = false;
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this._visitorKeys = null;
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this._enter = null;
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this._leave = null;
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}
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/**
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* @returns {ASTNode} The current node.
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*/
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current() {
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return this._current;
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}
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/**
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* @returns {ASTNode[]} The ancestor nodes.
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*/
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parents() {
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return this._parents.slice(0);
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}
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/**
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* Break the current traversal.
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* @returns {void}
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*/
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break() {
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this._broken = true;
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}
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/**
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* Skip child nodes for the current traversal.
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* @returns {void}
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*/
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skip() {
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this._skipped = true;
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}
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/**
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* Traverse the given AST tree.
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* @param {ASTNode} node The root node to traverse.
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* @param {Object} options The option object.
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* @param {Object} [options.visitorKeys=DEFAULT_VISITOR_KEYS] The keys of each node types to traverse child nodes. Default is `./default-visitor-keys.json`.
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* @param {Function} [options.enter=noop] The callback function which is called on entering each node.
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* @param {Function} [options.leave=noop] The callback function which is called on leaving each node.
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* @returns {void}
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*/
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traverse(node, options) {
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this._current = null;
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this._parents = [];
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this._skipped = false;
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this._broken = false;
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this._visitorKeys = options.visitorKeys || vk.KEYS;
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this._enter = options.enter || noop;
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this._leave = options.leave || noop;
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this._traverse(node, null);
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}
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/**
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* Traverse the given AST tree recursively.
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* @param {ASTNode} node The current node.
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* @param {ASTNode|null} parent The parent node.
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* @returns {void}
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* @private
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*/
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_traverse(node, parent) {
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if (!isNode(node)) {
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return;
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}
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this._current = node;
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this._skipped = false;
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this._enter(node, parent);
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if (!this._skipped && !this._broken) {
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const keys = getVisitorKeys(this._visitorKeys, node);
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if (keys.length >= 1) {
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this._parents.push(node);
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for (let i = 0; i < keys.length && !this._broken; ++i) {
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const child = node[keys[i]];
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if (Array.isArray(child)) {
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for (let j = 0; j < child.length && !this._broken; ++j) {
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this._traverse(child[j], node);
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}
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} else {
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this._traverse(child, node);
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}
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}
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this._parents.pop();
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}
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}
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if (!this._broken) {
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this._leave(node, parent);
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}
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this._current = parent;
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}
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/**
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* Calculates the keys to use for traversal.
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* @param {ASTNode} node The node to read keys from.
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* @returns {string[]} An array of keys to visit on the node.
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* @private
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*/
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static getKeys(node) {
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return vk.getKeys(node);
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}
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/**
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* Traverse the given AST tree.
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* @param {ASTNode} node The root node to traverse.
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* @param {Object} options The option object.
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* @param {Object} [options.visitorKeys=DEFAULT_VISITOR_KEYS] The keys of each node types to traverse child nodes. Default is `./default-visitor-keys.json`.
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* @param {Function} [options.enter=noop] The callback function which is called on entering each node.
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* @param {Function} [options.leave=noop] The callback function which is called on leaving each node.
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* @returns {void}
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*/
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static traverse(node, options) {
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new Traverser().traverse(node, options);
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}
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/**
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* The default visitor keys.
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* @type {Object}
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*/
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static get DEFAULT_VISITOR_KEYS() {
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return vk.KEYS;
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}
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}
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module.exports = Traverser;
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