fix: Avoid flatTree memory leak

lib/core/base/context.js

@@ -129,7 +129,7 @@ function parseSelectorArray(context, type) {
 			nodeList = Array.from(document.querySelectorAll(item));
 			//eslint no-loop-func:0
 			result = result.concat(nodeList.map((node) => {
-				return axe.utils.getNodeFromTree(axe._tree[0], node);
+				return axe.utils.getNodeFromTree(context.flatTree[0], node);
 			}));
 			break;
 		} else if (item && item.length && !(item instanceof Node)) {
@@ -140,14 +140,14 @@ function parseSelectorArray(context, type) {
 				nodeList = Array.from(document.querySelectorAll(item[0]));
 				//eslint no-loop-func:0
 				result = result.concat(nodeList.map((node) => {
-					return axe.utils.getNodeFromTree(axe._tree[0], node);
+					return axe.utils.getNodeFromTree(context.flatTree[0], node);
 				}));
 			}
 		} else if (item instanceof Node) {
 			if (item.documentElement instanceof Node) {
-				result.push(axe._tree[0]);
+				result.push(context.flatTree[0]);
 			} else {
-				result.push(axe.utils.getNodeFromTree(axe._tree[0], item));
+				result.push(axe.utils.getNodeFromTree(context.flatTree[0], item));
 			}
 		}
 	}
@@ -232,7 +232,7 @@ function Context(spec) {
 	spec = normalizeContext(spec);
 
 	//cache the flattened tree
-	axe._tree = axe.utils.getFlattenedTree(getRootNode(spec));
+	this.flatTree = axe.utils.getFlattenedTree(getRootNode(spec));
 	this.exclude = spec.exclude;
 	this.include = spec.include;
 

lib/core/public/run-rules.js

@@ -1,6 +1,13 @@
 /*global Context */
 /*exported runRules */
 
+function complete (cb, ...args) {
+	cb(...args);
+	// Clean up after resolve / reject
+	axe._tree = undefined;
+	axe._selectorData = undefined;
+}
+
 /**
  * Starts analysis on the current document and its subframes
  * @private
@@ -12,8 +19,10 @@ function runRules(context, options, resolve, reject) {
 	'use strict';
 	try {
 		context = new Context(context);
+		axe._tree = context.flatTree;
+		axe._selectorData = axe.utils.getSelectorData(context.flatTree);
 	} catch (e) {
-		return reject(e);
+		return complete(reject, e);
 	}
 
 	var q = axe.utils.queue();
@@ -45,10 +54,8 @@ function runRules(context, options, resolve, reject) {
 			}
 
 			// Add wrapper object so that we may use the same "merge" function for results from inside and outside frames
-			var results = axe.utils.mergeResults(data.map(function (d) {
-				return {
-					results: d
-				};
+			var results = axe.utils.mergeResults(data.map(function (results) {
+				return { results };
 			}));
 
 			// after should only run once, so ensure we are in the top level window
@@ -59,14 +66,16 @@ function runRules(context, options, resolve, reject) {
 				results = results.map(axe.utils.finalizeRuleResult);
 			}
 			try {
-				resolve(results);
+				complete(resolve, results);
 			} catch(e) {
-				axe.log(e);
+				complete(axe.log, e);
 			}
 		} catch (e) {
-			reject(e);
+			complete(reject, e);
 		}
-	}).catch(reject);
+	}).catch((e) => {
+		complete(reject, e);
+	});
 }
 
 axe._runRules = runRules;

lib/core/public/run.js

@@ -128,8 +128,6 @@ axe.run = function (context, options, callback) {
 		try {
 			let reporter = axe.getReporter(options.reporter);
 			let results = reporter(rawResults, options, respond);
-			axe._selectorData = undefined;
-			axe._tree = undefined;
 			if (results !== undefined) {
 				respond(results);
 			}

lib/core/utils/get-selector.js

@@ -307,11 +307,9 @@ function getThreeLeastCommonFeatures(elm, selectorData) {
 function generateSelector (elm, options, doc) {
 	/*eslint max-statements:["error", 22], no-loop-func:0*/
 	if (!axe._selectorData) {
-		axe._selectorData = axe.utils.getSelectorData(axe._tree);
+		throw new Error('Expect axe._selectorData to be set up');
 	}
-	const {
-		toRoot = false
-	} = options;
+	const { toRoot = false } = options;
 	let selector;
 	let similar;
 

test/core/base/context.js

@@ -327,11 +327,10 @@ describe('Context', function() {
 			});
 		});
 
-		it('should assign the result of getFlattenedTree to axe._tree', function () {
-			/* eslint no-new:0 */
-			new Context({ include: [document] });
+		it('should create a flatTree property', function () {
+			var context = new Context({ include: [document] });
 			// WARNING: This only works because there is now Shadow DOM on this page
-			assert.deepEqual(axe._tree, axe.utils.getFlattenedTree(document));
+			assert.deepEqual(context.flatTree, axe.utils.getFlattenedTree(document));
 		});
 
 		it('should throw when frame could not be found', function (done) {
@@ -350,27 +349,29 @@ describe('Context', function() {
 
 	describe('object definition', function() {
 		it('should assign include/exclude', function() {
-
+			var flatTree = axe.utils.getFlattenedTree(document);
 			assert.deepEqual(new Context({
 				include: ['#fixture'],
 				exclude: ['#mocha']
 			}), {
-				include: [axe.utils.getFlattenedTree(document.getElementById('fixture'))[0]],
-				exclude: [axe.utils.getFlattenedTree(document.getElementById('mocha'))[0]],
+				include: axe.utils.querySelectorAll(flatTree, '#fixture'),
+				exclude: axe.utils.querySelectorAll(flatTree, '#mocha'),
+				flatTree: flatTree,
 				initiator: true,
 				page: false,
 				frames: []
 			});
-
 		});
-		it('should disregard bad input, non-matching selectors', function() {
 
+		it('should disregard bad input, non-matching selectors', function() {
+			var flatTree = axe.utils.getFlattenedTree(document);
 			assert.deepEqual(new Context({
 				include: ['#fixture', '#monkeys'],
 				exclude: ['#bananas']
 			}), {
-				include: [axe.utils.getFlattenedTree(document.getElementById('fixture'))[0]],
+				include: axe.utils.querySelectorAll(flatTree, '#fixture'),
 				exclude: [],
+				flatTree: flatTree,
 				initiator: true,
 				page: false,
 				frames: []

test/core/public/run-rules.js

@@ -650,4 +650,51 @@ describe('runRules', function () {
 			done();
 		}, isNotCalled);
 	});
+
+	it('should clear up axe._tree / axe._selectorData after resolving', function (done) {
+		axe._load({ rules: [{
+			id: 'html',
+			selector: 'html',
+			any: ['html']
+		}], checks: [{
+			id: 'html',
+			evaluate: function () {
+				return true;
+			}
+		}], messages: {}});
+
+		runRules(document, {}, function resolve() {
+			assert.isDefined(axe._tree);
+			assert.isDefined(axe._selectorData);
+			setTimeout(function () {
+				assert.isUndefined(axe._tree);
+				assert.isUndefined(axe._selectorData);
+				done();
+			}, 10);
+		}, isNotCalled);
+	});
+
+	it('should clear up axe._tree / axe._selectorData after an error', function (done) {
+		axe._load({ rules: [{
+			id: 'invalidRule'
+		}], checks: [], messages: {}});
+
+		createFrames(function () {
+			setTimeout(function () {
+				runRules(document, {}, function () {
+					assert.ok(false, 'You shall not pass!');
+					done();
+				},
+				function () {
+					assert.isDefined(axe._tree);
+					assert.isDefined(axe._selectorData);
+					setTimeout(function () {
+						assert.isUndefined(axe._tree);
+						assert.isUndefined(axe._selectorData);
+						done();
+					}, 10);
+				});
+			}, 100);
+		});
+	});
 });

test/core/utils/collect-results-from-frames.js

@@ -5,6 +5,14 @@ describe('axe.utils.collectResultsFromFrames', function () {
 	var fixture = document.getElementById('fixture');
 	var noop = function () {};
 
+	function contextSetup (scope) {
+		var context = new Context(scope);
+		axe._tree = context.flatTree;
+		axe._selectorData = axe.utils.getSelectorData(context.flatTree);
+
+		return context
+	}
+
 	afterEach(function () {
 		fixture.innerHTML = '';
 		axe._tree = undefined;
@@ -25,8 +33,7 @@ describe('axe.utils.collectResultsFromFrames', function () {
 
 		var frame = document.createElement('iframe');
 		frame.addEventListener('load', function () {
-			var context = new Context(document);
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+			var context = contextSetup(document);
 			axe.utils.collectResultsFromFrames(context, {}, 'stuff', 'morestuff', noop,
 				function (err) {
 					assert.instanceOf(err, Error);
@@ -40,7 +47,6 @@ describe('axe.utils.collectResultsFromFrames', function () {
 		frame.id = 'level0';
 		frame.src = '../mock/frames/results-timeout.html';
 		fixture.appendChild(frame);
-
 	});
 
 	it('should override the timeout with `options.frameWaitTime`, if provided', function (done) {
@@ -57,9 +63,9 @@ describe('axe.utils.collectResultsFromFrames', function () {
 
 		var frame = document.createElement('iframe');
 		frame.addEventListener('load', function () {
-			var context = new Context(document);
+			var context = contextSetup(document);
 			var params = { frameWaitTime: 90000 };
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+
 			axe.utils.collectResultsFromFrames(context, params, 'stuff', 'morestuff', noop,
 				function (err) {
 					assert.instanceOf(err, Error);
@@ -73,7 +79,6 @@ describe('axe.utils.collectResultsFromFrames', function () {
 		frame.id = 'level0';
 		frame.src = '../mock/frames/results-timeout.html';
 		fixture.appendChild(frame);
-
 	});
 
 	it('should not throw given a recursive iframe', function (done) {
@@ -93,8 +98,8 @@ describe('axe.utils.collectResultsFromFrames', function () {
 
 		var frame = document.createElement('iframe');
 		frame.addEventListener('load', function () {
-			var context = new Context(document);
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+			var context = contextSetup(document);
+
 			axe.utils.collectResultsFromFrames(context, {}, 'rules', 'morestuff', function () {
 				done();
 			}, function (e) {
@@ -106,14 +111,12 @@ describe('axe.utils.collectResultsFromFrames', function () {
 		frame.id = 'level0';
 		frame.src = '../mock/frames/nested0.html';
 		fixture.appendChild(frame);
-
 	});
 
 	it('returns errors send from the frame', function (done) {
 		var frame = document.createElement('iframe');
 		frame.addEventListener('load', function () {
-			var context = new Context(document);
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+			var context = contextSetup(document);
 			axe.utils.collectResultsFromFrames(context, {}, 'command', 'params', noop,
 				function (err) {
 					assert.instanceOf(err, Error);

test/core/utils/dq-element.js

@@ -3,6 +3,7 @@ describe('DqElement', function () {
 	'use strict';
 
 	var fixture = document.getElementById('fixture');
+	var fixtureSetup = axe.testUtils.fixtureSetup;
 
 	afterEach(function () {
 		fixture.innerHTML = '';
@@ -33,7 +34,8 @@ describe('DqElement', function () {
 
 		it('should not be present in stringified version', function () {
 			var div = document.createElement('div');
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+			fixtureSetup();
+
 			var dqEl = new DqElement(div);
 
 			assert.isUndefined(JSON.parse(JSON.stringify(dqEl)).element);
@@ -141,8 +143,8 @@ describe('DqElement', function () {
 
 	describe('absolutePaths', function () {
 		it('creates a path all the way to root', function () {
-			fixture.innerHTML = '<div id="foo" class="bar">Hello!</div>';
-			axe._tree = axe.utils.getFlattenedTree(document.documentElement);
+			fixtureSetup('<div id="foo" class="bar">Hello!</div>');
+
 			var result = new DqElement(fixture.firstChild, {
 				absolutePaths: true
 			});