From 8dd83920c45da55ab41e515ad771d0d8bced1656 Mon Sep 17 00:00:00 2001
From: Pierre-Marie Dartus <dartus.pierremarie@gmail.com>
Date: Tue, 22 May 2018 16:28:27 -0700
Subject: [PATCH] fix: getRootNode when composed is false and the element is
 the root (#337)

## Details

Fix error throw in getRootNode when the component is the root of the component tree.

## Does this PR introduce a breaking change?

* [ ] Yes
* [X] No
---
 .../src/framework/__tests__/dom.spec.ts       | 58 ++--------------
 packages/lwc-engine/src/framework/dom.ts      | 66 +++++++++++++------
 2 files changed, 53 insertions(+), 71 deletions(-)

diff --git a/packages/lwc-engine/src/framework/__tests__/dom.spec.ts b/packages/lwc-engine/src/framework/__tests__/dom.spec.ts
index 3236d3cce4..e0bced4c07 100644
--- a/packages/lwc-engine/src/framework/__tests__/dom.spec.ts
+++ b/packages/lwc-engine/src/framework/__tests__/dom.spec.ts
@@ -50,34 +50,12 @@ describe('dom', () => {
         });
 
         it('should return correct value from self', () => {
-            class Parent extends Element {
-                handleFoo(evt) {
-                    expect(evt.target).toBe(this.template.querySelector('x-foo'));
-                }
-
-                render() {
-                    return ($api, $cmp) => {
-                        return [
-                            $api.h(
-                                'div',
-                                {
-                                    on: {
-                                        foo: $api.b($cmp.handleFoo)
-                                    },
-                                    key: 0,
-                                },
-                                []
-                            )
-                        ]
-                    }
-                }
-            }
-
+            class Parent extends Element {}
             const elm = createElement('x-parent', { is: Parent });
             document.body.appendChild(elm);
+
             const match = getRootNode.call(elm, { composed: true });
-            // We can't assert against document directly, because
-            // for some reasons, jest is locking up with document here
+
             expect(match.nodeName).toBe('#document');
         });
     });
@@ -129,34 +107,12 @@ describe('dom', () => {
         });
 
         it('should return correct value from self', () => {
-            class Parent extends Element {
-                handleFoo(evt) {
-                    expect(evt.target).toBe(this.template.querySelector('x-foo'));
-                }
-
-                render() {
-                    return ($api, $cmp) => {
-                        return [
-                            $api.h(
-                                'div',
-                                {
-                                    on: {
-                                        foo: $api.b($cmp.handleFoo)
-                                    },
-                                    key: 0,
-                                },
-                                []
-                            )
-                        ]
-                    }
-                }
-            }
-
+            class Parent extends Element {}
             const elm = createElement('x-parent', { is: Parent });
             document.body.appendChild(elm);
-            const match = getRootNode.call(elm, { composed: true });
-            // We can't assert against document directly, because
-            // for some reasons, jest is locking up with document here
+
+            const match = getRootNode.call(elm, { composed: false });
+
             expect(match.nodeName).toBe('#document');
         });
     });
diff --git a/packages/lwc-engine/src/framework/dom.ts b/packages/lwc-engine/src/framework/dom.ts
index cec6272e9b..68122bd85d 100644
--- a/packages/lwc-engine/src/framework/dom.ts
+++ b/packages/lwc-engine/src/framework/dom.ts
@@ -9,6 +9,7 @@ import {
     getOwnPropertyDescriptor,
     isUndefined,
     isNull,
+    isTrue,
     defineProperties,
 } from './language';
 import { ViewModelReflection } from "./utils";
@@ -35,34 +36,59 @@ const {
     compareDocumentPosition,
 } = Node.prototype;
 
-function findShadowRoot(node) {
-    let root = node;
-    while (isUndefined(root[ViewModelReflection])) {
-        root = root.parentNode;
+/**
+ * Returns the context shadow included root.
+ */
+function findShadowRoot(node: Node): Node {
+    // We need to ensure that the parent element is present before accessing it.
+    if (isNull(node.parentNode)) {
+        return node;
     }
-    return root;
+
+    // In the case of LWC, the root and the host element are the same things. Therefor,
+    // when calling findShadowRoot on the a host element we want to return the parent host
+    // element and not the current host element.
+    node = node.parentNode;
+    while (
+        !isNull(node.parentNode) &&
+        isUndefined(node[ViewModelReflection])
+    ) {
+        node = node.parentNode;
+    }
+
+    return node;
 }
 
-function findComposedRootNode(node: Node) {
-    while (node !== document) {
-        const parent = node.parentNode;
-        if (isNull(parent)) {
-            return node;
-        }
-        node = parent;
+/**
+ * Returns the context root beyond the shadow root.
+ *
+ * It doesn't returns actually the root but the host. This approximation is sufficiant
+ * in our case.
+ */
+function findComposedRootNode(node: Node): Node {
+    while (!isNull(node.parentNode)) {
+        node = node.parentNode;
     }
+
     return node;
 }
 
-// TODO: once we start using the real shadowDOM, we can rely on:
-// const { getRootNode } = Node.prototype;
-// for now, we need to provide a dummy implementation to provide retargeting
-function getRootNode(this: Node, options: Record<string, any> | undefined): Node {
+/**
+ * Dummy implementation of the Node.prototype.getRootNode.
+ * Spec: https://dom.spec.whatwg.org/#dom-node-getrootnode
+ *
+ * TODO: Once we start using the real shadowDOM, this method should be replaced by:
+ * const { getRootNode } = Node.prototype;
+ */
+function getRootNode(
+    this: Node,
+    options?: { composed?: boolean }
+): Node {
     const composed: boolean = isUndefined(options) ? false : !!options.composed;
-    if (!composed) {
-        return findShadowRoot(this.parentNode); // this is not quite the root (it is the host), but for us is sufficient
-    }
-    return findComposedRootNode(this);
+
+    return isTrue(composed) ?
+        findComposedRootNode(this) :
+        findShadowRoot(this);
 }
 
 export function isChildNode(root: Element, node: Node): boolean {