From 46a5d110a904ba7939343b94cd6ee2864f51c0aa Mon Sep 17 00:00:00 2001
From: Adam Cutler <adam.r.cutler@gmail.com>
Date: Wed, 31 Jul 2019 16:24:01 -0400
Subject: [PATCH] fix(flatten-tree): do not call deprecated getDistributedNodes
 (#1729)

---
 lib/core/utils/flattened-tree.js  |  5 ++++-
 test/core/utils/flattened-tree.js | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/core/utils/flattened-tree.js b/lib/core/utils/flattened-tree.js
index 2e40c9d69b..0a2e8136f5 100644
--- a/lib/core/utils/flattened-tree.js
+++ b/lib/core/utils/flattened-tree.js
@@ -80,7 +80,10 @@ function flattenTree(node, shadowId, parent) {
 
 		return [retVal];
 	} else {
-		if (nodeName === 'content') {
+		if (
+			nodeName === 'content' &&
+			typeof node.getDistributedNodes === 'function'
+		) {
 			realArray = Array.from(node.getDistributedNodes());
 			return realArray.reduce((res, child) => {
 				return reduceShadowDOM(res, child, parent);
diff --git a/test/core/utils/flattened-tree.js b/test/core/utils/flattened-tree.js
index 739347daa8..66ce30968b 100644
--- a/test/core/utils/flattened-tree.js
+++ b/test/core/utils/flattened-tree.js
@@ -291,6 +291,21 @@ describe('axe.utils.getFlattenedTree', function() {
 				assert.isDefined(vNode);
 				assert.equal(virtualDOM[0].actualNode, vNode.actualNode);
 			});
+			it('should not throw if getDistributedNodes is missing', function() {
+				var getDistributedNodes = fixture.getDistributedNodes;
+				fixture.getDistributedNodes = undefined;
+				try {
+					var virtualDOM = axe.utils.getFlattenedTree(fixture);
+					var vNode = axe.utils.getNodeFromTree(
+						virtualDOM[0],
+						virtualDOM[0].actualNode
+					);
+					assert.isDefined(vNode);
+					assert.equal(virtualDOM[0].actualNode, vNode.actualNode);
+				} finally {
+					fixture.getDistributedNodes = getDistributedNodes;
+				}
+			});
 		});
 	} else {
 		it('does not throw when slot elements are used', function() {