/** * @fileoverview The event generator for AST nodes. * @author Toru Nagashima */ "use strict"; //------------------------------------------------------------------------------ // Requirements //------------------------------------------------------------------------------ const esquery = require("esquery"); const lodash = require("lodash"); //------------------------------------------------------------------------------ // Typedefs //------------------------------------------------------------------------------ /** * An object describing an AST selector * @typedef {Object} ASTSelector * @property {string} rawSelector The string that was parsed into this selector * @property {boolean} isExit `true` if this should be emitted when exiting the node rather than when entering * @property {Object} parsedSelector An object (from esquery) describing the matching behavior of the selector * @property {string[]|null} listenerTypes A list of node types that could possibly cause the selector to match, * or `null` if all node types could cause a match * @property {number} attributeCount The total number of classes, pseudo-classes, and attribute queries in this selector * @property {number} identifierCount The total number of identifier queries in this selector */ //------------------------------------------------------------------------------ // Helpers //------------------------------------------------------------------------------ /** * Gets the possible types of a selector * @param {Object} parsedSelector An object (from esquery) describing the matching behavior of the selector * @returns {string[]|null} The node types that could possibly trigger this selector, or `null` if all node types could trigger it */ function getPossibleTypes(parsedSelector) { switch (parsedSelector.type) { case "identifier": return [parsedSelector.value]; case "matches": { const typesForComponents = parsedSelector.selectors.map(getPossibleTypes); if (typesForComponents.every(Boolean)) { return lodash.union(...typesForComponents); } return null; } case "compound": { const typesForComponents = parsedSelector.selectors.map(getPossibleTypes).filter(typesForComponent => typesForComponent); // If all of the components could match any type, then the compound could also match any type. if (!typesForComponents.length) { return null; } /* * If at least one of the components could only match a particular type, the compound could only match * the intersection of those types. */ return lodash.intersection(...typesForComponents); } case "child": case "descendant": case "sibling": case "adjacent": return getPossibleTypes(parsedSelector.right); default: return null; } } /** * Counts the number of class, pseudo-class, and attribute queries in this selector * @param {Object} parsedSelector An object (from esquery) describing the selector's matching behavior * @returns {number} The number of class, pseudo-class, and attribute queries in this selector */ function countClassAttributes(parsedSelector) { switch (parsedSelector.type) { case "child": case "descendant": case "sibling": case "adjacent": return countClassAttributes(parsedSelector.left) + countClassAttributes(parsedSelector.right); case "compound": case "not": case "matches": return parsedSelector.selectors.reduce((sum, childSelector) => sum + countClassAttributes(childSelector), 0); case "attribute": case "field": case "nth-child": case "nth-last-child": return 1; default: return 0; } } /** * Counts the number of identifier queries in this selector * @param {Object} parsedSelector An object (from esquery) describing the selector's matching behavior * @returns {number} The number of identifier queries */ function countIdentifiers(parsedSelector) { switch (parsedSelector.type) { case "child": case "descendant": case "sibling": case "adjacent": return countIdentifiers(parsedSelector.left) + countIdentifiers(parsedSelector.right); case "compound": case "not": case "matches": return parsedSelector.selectors.reduce((sum, childSelector) => sum + countIdentifiers(childSelector), 0); case "identifier": return 1; default: return 0; } } /** * Compares the specificity of two selector objects, with CSS-like rules. * @param {ASTSelector} selectorA An AST selector descriptor * @param {ASTSelector} selectorB Another AST selector descriptor * @returns {number} * a value less than 0 if selectorA is less specific than selectorB * a value greater than 0 if selectorA is more specific than selectorB * a value less than 0 if selectorA and selectorB have the same specificity, and selectorA <= selectorB alphabetically * a value greater than 0 if selectorA and selectorB have the same specificity, and selectorA > selectorB alphabetically */ function compareSpecificity(selectorA, selectorB) { return selectorA.attributeCount - selectorB.attributeCount || selectorA.identifierCount - selectorB.identifierCount || (selectorA.rawSelector <= selectorB.rawSelector ? -1 : 1); } /** * Parses a raw selector string, and throws a useful error if parsing fails. * @param {string} rawSelector A raw AST selector * @returns {Object} An object (from esquery) describing the matching behavior of this selector * @throws {Error} An error if the selector is invalid */ function tryParseSelector(rawSelector) { try { return esquery.parse(rawSelector.replace(/:exit$/u, "")); } catch (err) { if (err.location && err.location.start && typeof err.location.start.offset === "number") { throw new SyntaxError(`Syntax error in selector "${rawSelector}" at position ${err.location.start.offset}: ${err.message}`); } throw err; } } /** * Parses a raw selector string, and returns the parsed selector along with specificity and type information. * @param {string} rawSelector A raw AST selector * @returns {ASTSelector} A selector descriptor */ const parseSelector = lodash.memoize(rawSelector => { const parsedSelector = tryParseSelector(rawSelector); return { rawSelector, isExit: rawSelector.endsWith(":exit"), parsedSelector, listenerTypes: getPossibleTypes(parsedSelector), attributeCount: countClassAttributes(parsedSelector), identifierCount: countIdentifiers(parsedSelector) }; }); //------------------------------------------------------------------------------ // Public Interface //------------------------------------------------------------------------------ /** * The event generator for AST nodes. * This implements below interface. * * ```ts * interface EventGenerator { * emitter: SafeEmitter; * enterNode(node: ASTNode): void; * leaveNode(node: ASTNode): void; * } * ``` */ class NodeEventGenerator { // eslint-disable-next-line jsdoc/require-description /** * @param {SafeEmitter} emitter * An SafeEmitter which is the destination of events. This emitter must already * have registered listeners for all of the events that it needs to listen for. * (See lib/linter/safe-emitter.js for more details on `SafeEmitter`.) * @param {ESQueryOptions} esqueryOptions `esquery` options for traversing custom nodes. * @returns {NodeEventGenerator} new instance */ constructor(emitter, esqueryOptions) { this.emitter = emitter; this.esqueryOptions = esqueryOptions; this.currentAncestry = []; this.enterSelectorsByNodeType = new Map(); this.exitSelectorsByNodeType = new Map(); this.anyTypeEnterSelectors = []; this.anyTypeExitSelectors = []; emitter.eventNames().forEach(rawSelector => { const selector = parseSelector(rawSelector); if (selector.listenerTypes) { const typeMap = selector.isExit ? this.exitSelectorsByNodeType : this.enterSelectorsByNodeType; selector.listenerTypes.forEach(nodeType => { if (!typeMap.has(nodeType)) { typeMap.set(nodeType, []); } typeMap.get(nodeType).push(selector); }); return; } const selectors = selector.isExit ? this.anyTypeExitSelectors : this.anyTypeEnterSelectors; selectors.push(selector); }); this.anyTypeEnterSelectors.sort(compareSpecificity); this.anyTypeExitSelectors.sort(compareSpecificity); this.enterSelectorsByNodeType.forEach(selectorList => selectorList.sort(compareSpecificity)); this.exitSelectorsByNodeType.forEach(selectorList => selectorList.sort(compareSpecificity)); } /** * Checks a selector against a node, and emits it if it matches * @param {ASTNode} node The node to check * @param {ASTSelector} selector An AST selector descriptor * @returns {void} */ applySelector(node, selector) { if (esquery.matches(node, selector.parsedSelector, this.currentAncestry, this.esqueryOptions)) { this.emitter.emit(selector.rawSelector, node); } } /** * Applies all appropriate selectors to a node, in specificity order * @param {ASTNode} node The node to check * @param {boolean} isExit `false` if the node is currently being entered, `true` if it's currently being exited * @returns {void} */ applySelectors(node, isExit) { const selectorsByNodeType = (isExit ? this.exitSelectorsByNodeType : this.enterSelectorsByNodeType).get(node.type) || []; const anyTypeSelectors = isExit ? this.anyTypeExitSelectors : this.anyTypeEnterSelectors; /* * selectorsByNodeType and anyTypeSelectors were already sorted by specificity in the constructor. * Iterate through each of them, applying selectors in the right order. */ let selectorsByTypeIndex = 0; let anyTypeSelectorsIndex = 0; while (selectorsByTypeIndex < selectorsByNodeType.length || anyTypeSelectorsIndex < anyTypeSelectors.length) { if ( selectorsByTypeIndex >= selectorsByNodeType.length || anyTypeSelectorsIndex < anyTypeSelectors.length && compareSpecificity(anyTypeSelectors[anyTypeSelectorsIndex], selectorsByNodeType[selectorsByTypeIndex]) < 0 ) { this.applySelector(node, anyTypeSelectors[anyTypeSelectorsIndex++]); } else { this.applySelector(node, selectorsByNodeType[selectorsByTypeIndex++]); } } } /** * Emits an event of entering AST node. * @param {ASTNode} node A node which was entered. * @returns {void} */ enterNode(node) { if (node.parent) { this.currentAncestry.unshift(node.parent); } this.applySelectors(node, false); } /** * Emits an event of leaving AST node. * @param {ASTNode} node A node which was left. * @returns {void} */ leaveNode(node) { this.applySelectors(node, true); this.currentAncestry.shift(); } } module.exports = NodeEventGenerator;