From ee690f6de6da20ef241bff3364dad88fe525942a Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Mon, 11 Mar 2019 18:12:43 -0700
Subject: [PATCH 1/3] Schedules `requestUpdate` in `initialize` rather than
 `connectedCallback`

Fixes #594. Ensures an early access of `updateComplete` will not complete before the element has first updated (at connection time).
---
 src/lib/updating-element.ts           |  6 +++---
 src/test/lib/updating-element_test.ts | 28 ++++++++++++++++++++++-----
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/src/lib/updating-element.ts b/src/lib/updating-element.ts
index abb2fd93..dde4f4c7 100644
--- a/src/lib/updating-element.ts
+++ b/src/lib/updating-element.ts
@@ -441,6 +441,8 @@ export abstract class UpdatingElement extends HTMLElement {
    */
   protected initialize() {
     this._saveInstanceProperties();
+    // ensures first update will be caught by an early access of `updateComplete`
+    this.requestUpdate();
   }
 
   /**
@@ -484,15 +486,13 @@ export abstract class UpdatingElement extends HTMLElement {
 
   connectedCallback() {
     this._updateState = this._updateState | STATE_HAS_CONNECTED;
-    // Ensure connection triggers an update. Updates cannot complete before
+    // Ensure first connection completes an update. Updates cannot complete before
     // connection and if one is pending connection the `_hasConnectionResolver`
     // will exist. If so, resolve it to complete the update, otherwise
     // requestUpdate.
     if (this._hasConnectedResolver) {
       this._hasConnectedResolver();
       this._hasConnectedResolver = undefined;
-    } else {
-      this.requestUpdate();
     }
   }
 
diff --git a/src/test/lib/updating-element_test.ts b/src/test/lib/updating-element_test.ts
index 8daa277f..062ce89b 100644
--- a/src/test/lib/updating-element_test.ts
+++ b/src/test/lib/updating-element_test.ts
@@ -2202,11 +2202,6 @@ suite('UpdatingElement', () => {
 
       @property() foo = 5;
 
-      constructor() {
-        super();
-        this.requestUpdate();
-      }
-
       updated(_changedProperties: Map<PropertyKey, unknown>) {
         this.updatedCalledCount++;
       }
@@ -2219,4 +2214,27 @@ suite('UpdatingElement', () => {
     await a.updateComplete;
     assert.equal(a.updatedCalledCount, 1);
   });
+
+  test('early access of updateComplete waits until first update', async() => {
+    class A extends UpdatingElement {
+      didUpdate = false;
+
+      updated(_changedProperties: Map<PropertyKey, unknown>) {
+        this.didUpdate = true;
+      }
+    }
+    customElements.define(generateElementName(), A);
+    const a = new A();
+    let updated = false;
+    a.updateComplete.then(() => {
+      updated = true;
+      assert.isTrue(a.didUpdate);
+    });
+    await new Promise((r) => setTimeout(r, 20));
+    assert.isFalse(updated);
+    document.body.appendChild(a);
+    await a.updateComplete;
+    assert.isTrue(updated);
+    document.body.removeChild(a);
+  });
 });

From 6c26450c75eeb301e5efc14ce6b09cd9dbbc8e7e Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Mon, 11 Mar 2019 18:15:27 -0700
Subject: [PATCH 2/3] Update CHANGELOG.md

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index abcd3508..7cab50d2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 * `LitElement.renderRoot` is now `public readonly` instead of `protected`.
 
 ### Fixed
+* Initial update is scheduled at construction time rather than connected time ([#594](https://github.com/Polymer/lit-element/issues/594)).
 * Properties annotated with the `@query` and `@queryAll` decorators will now
   survive property renaming optimizations when used with tsickle and Closure JS
   Compiler.

From 4f4f078ea85904645525276df85f59181a13739d Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Tue, 12 Mar 2019 14:19:28 -0700
Subject: [PATCH 3/3] Update test to use helper to append/remove elements

---
 src/test/lib/updating-element_test.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/test/lib/updating-element_test.ts b/src/test/lib/updating-element_test.ts
index 062ce89b..0952c541 100644
--- a/src/test/lib/updating-element_test.ts
+++ b/src/test/lib/updating-element_test.ts
@@ -2232,9 +2232,8 @@ suite('UpdatingElement', () => {
     });
     await new Promise((r) => setTimeout(r, 20));
     assert.isFalse(updated);
-    document.body.appendChild(a);
+    container.appendChild(a);
     await a.updateComplete;
     assert.isTrue(updated);
-    document.body.removeChild(a);
   });
 });