From 0aa7b73e295e0503e7162497a3526bbe625ecb13 Mon Sep 17 00:00:00 2001
From: Alexander Marks <aomarks@google.com>
Date: Mon, 15 Jul 2019 12:06:13 -0700
Subject: [PATCH] Fix compatibility with JSC static property optimizations.

Fixes https://github.com/Polymer/lit-element/issues/732
---
 CHANGELOG.md                |  5 +++--
 src/lib/updating-element.ts | 21 +++++++++++++++------
 src/lit-element.ts          | 14 ++++++--------
 3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 505a261b..f1abfbca 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,11 +10,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
    Unreleased section, uncommenting the header as necessary.
 -->
 
-<!-- ## Unreleased -->
+## Unreleased
 <!-- ### Added -->
 <!-- ### Changed -->
 <!-- ### Removed -->
-<!-- ### Fixed -->
+### Fixed
+* Fixed compatibility with Closure JS Compiler optimizations relating to static properties ([#732](https://github.com/Polymer/lit-element/issues/732)).
 
 
 ## [2.2.0] - 2019-06-11
diff --git a/src/lib/updating-element.ts b/src/lib/updating-element.ts
index 67115918..14e0e5f2 100644
--- a/src/lib/updating-element.ts
+++ b/src/lib/updating-element.ts
@@ -12,6 +12,9 @@
  * http://polymer.github.io/PATENTS.txt
  */
 
+// So that custom elements work after compilation to es5.
+import 'goog:webcomponentsjs.custom_elements.auto_es5_shim';
+
 /**
  * When using Closure Compiler, JSCompiler_renameProperty(property, object) is
  * replaced at compile time by the munged name for object[property]. We cannot
@@ -211,10 +214,11 @@ export abstract class UpdatingElement extends HTMLElement {
   private static _attributeToPropertyMap: AttributeMap;
 
   /**
-   * Marks class as having finished creating properties.
+   * This property was previously used to record the classes that have already
+   * been finalized. This property is no longer used, but is still declared here
+   * for backwards compatability in TypeScript typings.
    */
-  protected static finalized = true;
-
+  protected static finalized : boolean|undefined;
   /**
    * Memoized list of all class properties, including any superclass properties.
    * Created lazily on user subclasses when finalizing the class.
@@ -315,8 +319,7 @@ export abstract class UpdatingElement extends HTMLElement {
    * @nocollapse
    */
   protected static finalize() {
-    if (this.hasOwnProperty(JSCompiler_renameProperty('finalized', this)) &&
-        this.finalized) {
+    if (finalized.has(this)) {
       return;
     }
     // finalize any superclasses
@@ -324,7 +327,7 @@ export abstract class UpdatingElement extends HTMLElement {
     if (typeof superCtor.finalize === 'function') {
       superCtor.finalize();
     }
-    this.finalized = true;
+    finalized.add(this);
     this._ensureClassProperties();
     // initialize Map populated in observedAttributes
     this._attributeToPropertyMap = new Map();
@@ -793,3 +796,9 @@ export abstract class UpdatingElement extends HTMLElement {
   protected firstUpdated(_changedProperties: PropertyValues) {
   }
 }
+
+/**
+ * Marks class as having finished creating properties.
+ */
+const finalized = new Set<typeof UpdatingElement>();
+finalized.add(UpdatingElement);
diff --git a/src/lit-element.ts b/src/lit-element.ts
index f5b9f446..366c6cea 100644
--- a/src/lit-element.ts
+++ b/src/lit-element.ts
@@ -59,12 +59,6 @@ const flattenStyles = (styles: CSSResultArray): CSSResult[] =>
     styles.flat ? styles.flat(Infinity) : arrayFlat(styles);
 
 export class LitElement extends UpdatingElement {
-  /**
-   * Ensure this class is marked as `finalized` as an optimization ensuring
-   * it will not needlessly try to `finalize`.
-   */
-  protected static finalized = true;
-
   /**
    * Render method used to render the lit-html TemplateResult to the element's
    * DOM.
@@ -85,7 +79,11 @@ export class LitElement extends UpdatingElement {
 
   /** @nocollapse */
   protected static finalize() {
-    super.finalize();
+    if (this !== LitElement) {
+      // The Closure JS Compiler does not always preserve the correct "this"
+      // when calling static super methods, so explicitly bind here.
+      super.finalize.apply(this);
+    }
     // Prepare styling that is stamped at first render time. Styling
     // is built from user provided `styles` or is inherited from the superclass.
     this._styles =
@@ -180,7 +178,7 @@ export class LitElement extends UpdatingElement {
     // (3) shadowRoot.adoptedStyleSheets polyfilled: append styles after
     // rendering
     if (window.ShadyCSS !== undefined && !window.ShadyCSS.nativeShadow) {
-      window.ShadyCSS.ScopingShim.prepareAdoptedCssText(
+      window.ShadyCSS.ScopingShim!.prepareAdoptedCssText(
           styles.map((s) => s.cssText), this.localName);
     } else if (supportsAdoptingStyleSheets) {
       (this.renderRoot as ShadowRoot).adoptedStyleSheets =