From 5b34ce9d8321e60cf46bc07205d02eb5f9b5abf6 Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Fri, 9 Nov 2018 11:39:10 -0800
Subject: [PATCH] Avoid copying certain properties from behaviors

This better matches what Polymer 1.x did for:
* hostAttributes
* listeners
* properties
* observers
---
 lib/legacy/class.html    | 33 ++++++++++++++++++++++-----------
 test/unit/behaviors.html | 21 +++++++++++++++++++++
 2 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/lib/legacy/class.html b/lib/legacy/class.html
index 4269b002ea..bed2211d53 100644
--- a/lib/legacy/class.html
+++ b/lib/legacy/class.html
@@ -14,7 +14,7 @@
 
     'use strict';
 
-    const metaProps = {
+    const lifecycleProps = {
       attached: true,
       detached: true,
       ready: true,
@@ -22,18 +22,29 @@
       beforeRegister: true,
       registered: true,
       attributeChanged: true,
+      listeners: true,
+      hostAttributes: true
     };
 
-    const excludeProps = Object.assign({
+    const excludeOnInfo = {
+      attached: true,
+      detached: true,
+      ready: true,
+      created: true,
+      beforeRegister: true,
+      registered: true,
+      attributeChanged: true,
       behaviors: true
-    }, metaProps);
+    };
 
-    const lifecycleProps = Object.assign({
+    const excludeOnBehaviors = Object.assign({
       listeners: true,
-      hostAttributes: true
-    }, metaProps);
+      hostAttributes: true,
+      properties: true,
+      observers: true,
+    }, excludeOnInfo);
 
-    function copyProperties(source, target) {
+    function copyProperties(source, target, excludeProps) {
       for (let p in source) {
         // NOTE: cannot copy `excludeProps` methods onto prototype at least because
         // `super.ready` must be called and is not included in the user fn.
@@ -97,12 +108,12 @@
     // (again same as 1.x)
     function applyBehaviors(proto, behaviors, lifecycle) {
       for (let i=0; i<behaviors.length; i++) {
-        applyInfo(proto, behaviors[i], lifecycle);
+        applyInfo(proto, behaviors[i], lifecycle, excludeOnBehaviors);
       }
     }
 
-    function applyInfo(proto, info, lifecycle) {
-      copyProperties(info, proto);
+    function applyInfo(proto, info, lifecycle, excludeProps) {
+      copyProperties(info, proto, excludeProps);
       for (let p in lifecycleProps) {
         if (info[p]) {
           lifecycle[p] = lifecycle[p] || [];
@@ -282,7 +293,7 @@
           if (behaviorList) {
             applyBehaviors(proto, behaviorList, lifecycle);
           }
-          applyInfo(proto, info, lifecycle);
+          applyInfo(proto, info, lifecycle, excludeOnInfo);
           let list = lifecycle.beforeRegister;
           if (list) {
             for (let i=0; i < list.length; i++) {
diff --git a/test/unit/behaviors.html b/test/unit/behaviors.html
index d7f23ea09a..4cafee3c28 100644
--- a/test/unit/behaviors.html
+++ b/test/unit/behaviors.html
@@ -64,6 +64,8 @@
         }
       },
 
+      observers: [],
+
       _simpleProperty: 'A',
 
       hostAttributes: {
@@ -371,6 +373,11 @@
       }
     });
 
+    Polymer({
+      is: 'behavior-properties',
+      behaviors: [window.BehaviorA]
+    });
+
   });
   </script>
 
@@ -434,6 +441,12 @@
     </template>
   </test-fixture>
 
+  <test-fixture id="behavior-properties">
+    <template>
+      <behavior-properties></behavior-properties>
+    </template>
+  </test-fixture>
+
 <script>
 
 suite('single behavior element', function() {
@@ -479,6 +492,14 @@
     assert.equal(el.computeA, true);
   });
 
+  test('special properties not copied from behavior to element', function() {
+    const el = fixture('behavior-properties');
+    assert.notOk(el.properties);
+    assert.notOk(el.observers);
+    assert.notOk(el.hostAttributes);
+    assert.notOk(el.listeners);
+  });
+
 });
 
 suite('behavior.registered', function() {