More updates based on code review.

lib/legacy/class.html

@@ -350,11 +350,6 @@
         Polymer.LegacyElementMixin(HTMLElement));
       // decorate klass with registration info
       klass.is = info.is;
-      // if user provided template on info, make sure the static _template
-      // is set so the static template getter uses it
-      if (info._template !== undefined) {
-        klass._template = info._template;
-      }
       return klass;
     };
 

lib/mixins/element-mixin.html

@@ -408,14 +408,14 @@
       static get template() {
         if (!this.hasOwnProperty(JSCompiler_renameProperty('_template', this))) {
           this._template =
+            // Take any template set on the prototype, including null (for legacy
+            // support, setting in registered callback, etc.)
+            this.prototype._template !== undefined ? this.prototype._template :
             // Look in dom-module associated with this element's is
             getTemplateFromDomModule(/** @type {PolymerElementConstructor}*/ (this).is) ||
             // Next look for superclass template (call the super impl this
             // way so that `this` points to the superclass)
-            Object.getPrototypeOf(/** @type {PolymerElementConstructor}*/ (this).prototype).constructor.template ||
-            // Finally, fall back to any _template set on prototype, e.g.
-            // via registered callback
-            this.prototype._template;
+            Object.getPrototypeOf(/** @type {PolymerElementConstructor}*/ (this).prototype).constructor.template;
         }
         return this._template;
       }

test/unit/behaviors.html

@@ -22,6 +22,12 @@
     </template>
   </dom-module>
 
+  <dom-module id="template-from-behavior">
+    <template>
+      <div id="from-base">should not be used</div>
+    </template>
+  </dom-module>
+
   <script>
   HTMLImports.whenReady(function() {
     window.BehaviorA = {
@@ -283,6 +289,51 @@
 
       is: 'behavior-registered'
     });
+
+    window.templateBehavior1 = {
+      _template: Polymer.html`<div id="from-behavior1"></div>`
+    };
+
+    window.templateBehavior2 = {
+      _template: Polymer.html`<div id="from-behavior2"></div>`
+    };
+
+    window.templateBehaviorFromRegister = {
+      registered: function() {
+        this._template = Polymer.html`<div id="behavior-from-register"></div>`;
+      }
+    };
+
+    Polymer({
+      is: 'template-from-registered',
+      registered: function() {
+        this._template = Polymer.html`<div id="from-registered"></div>`;
+      }
+    });
+
+    Polymer({
+      is: 'template-from-behavior',
+      behaviors: [
+        window.templateBehavior1
+      ]
+    });
+
+    Polymer({
+      is: 'template-from-behavior-overridden',
+      behaviors: [
+        window.templateBehavior1,
+        window.templateBehavior2
+      ]
+    });
+
+    Polymer({
+      is: 'template-from-behavior-registered',
+      behaviors: [
+        window.templateBehavior1,
+        templateBehaviorFromRegister
+      ]
+    });
+
   });
   </script>
 
@@ -309,6 +360,31 @@
       <behavior-registered></behavior-registered>
     </template>
   </test-fixture>
+
+  <test-fixture id="from-registered">
+    <template>
+      <template-from-registered></template-from-registered>
+    </template>
+  </test-fixture>
+
+  <test-fixture id="from-behavior">
+    <template>
+      <template-from-behavior></template-from-behavior>
+    </template>
+  </test-fixture>
+
+  <test-fixture id="from-behavior-overridden">
+    <template>
+      <template-from-behavior-overridden></template-from-behavior-overridden>
+    </template>
+  </test-fixture>
+
+  <test-fixture id="from-behavior-registered">
+    <template>
+      <template-from-behavior-registered></template-from-behavior-registered>
+    </template>
+  </test-fixture>
+
 <script>
 
 suite('single behavior element', function() {
@@ -505,6 +581,33 @@
 
 });
 
+suite('templates from behaviors', function() {
+
+  test('template from registered callback', function() {
+    var el = fixture('from-registered');
+    assert.ok(el.shadowRoot.querySelector('#from-registered'));
+  });
+
+  test('template from behavior', function() {
+    var el = fixture('from-behavior');
+    assert.notOk(el.shadowRoot.querySelector('#from-base'));
+    assert.ok(el.shadowRoot.querySelector('#from-behavior1'));
+  });
+
+  test('template from overriding behavior', function() {
+    var el = fixture('from-behavior-overridden');
+    assert.notOk(el.shadowRoot.querySelector('#from-behavior1'));
+    assert.ok(el.shadowRoot.querySelector('#from-behavior2'));
+  });
+
+  test('template from behavior registered callback', function() {
+    var el = fixture('from-behavior-registered');
+    assert.notOk(el.shadowRoot.querySelector('#from-behavior1'));
+    assert.ok(el.shadowRoot.querySelector('#behavior-from-register'));
+  });
+
+});
+
 </script>
 
 </body>

test/unit/strict-template-policy.html

@@ -157,11 +157,27 @@
             '  <template>' +
             '    <div id="injected"></div>'+
             '  </template>`' +
-            '</dom-module>' +
-            '<trusted-element></trusted-element>';
+            '</dom-module>';
         }, /trusted-element re-registered/);
-        const el = document.querySelector('trusted-element');
-        assert.notOk(el && el.shadowRoot && el.shadowRoot.querySelector('#injected'));
+        const el = document.createElement('trusted-element');
+        document.getElementById('target').appendChild(el);
+        assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
+      });
+
+      test('dom-module after registration, again', function() {
+        assertThrows(function() {
+          document.getElementById('target').innerHTML =
+            '<dom-module id="trusted-element">' +
+            '  <template>' +
+            '    <div id="injected"></div>'+
+            '  </template>`' +
+            '</dom-module>';
+        }, /trusted-element re-registered/);
+        const el = document.createElement('trusted-element');
+        document.getElementById('target').appendChild(el);
+        assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
       });
 
       test('dom-module before registration', function() {
@@ -179,6 +195,7 @@
         let el = document.createElement('has-no-template');
         document.getElementById('target').appendChild(el);
         assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
       });
 
       test('dom-module after registration (legacy)', function() {
@@ -188,11 +205,27 @@
             '  <template>' +
             '    <div id="injected"></div>'+
             '  </template>`' +
-            '</dom-module>' +
-            '<trusted-element-legacy></trusted-element-legacy>';
+            '</dom-module>';
         }, /trusted-element-legacy re-registered/);
-        const el = document.querySelector('trusted-element-legacy');
-        assert.notOk(el && el.shadowRoot && el.shadowRoot.querySelector('#injected'));
+        const el = document.createElement('trusted-element-legacy');
+        document.getElementById('target').appendChild(el);
+        assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
+      });
+
+      test('dom-module after registration, again (legacy)', function() {
+        assertThrows(function() {
+          document.getElementById('target').innerHTML =
+            '<dom-module id="trusted-element-legacy">' +
+            '  <template>' +
+            '    <div id="injected"></div>'+
+            '  </template>`' +
+            '</dom-module>';
+        }, /trusted-element-legacy re-registered/);
+        const el = document.createElement('trusted-element-legacy');
+        document.getElementById('target').appendChild(el);
+        assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
       });
 
       test('dom-module before registration (legacy)', function() {
@@ -208,7 +241,8 @@
         });
         let el = document.createElement('has-no-template-legacy');
         document.getElementById('target').appendChild(el);
-        assert.notOk(document.querySelector('has-no-template-legacy').shadowRoot);
+        assert.notOk(el.shadowRoot);
+        assert.notOk(document.getElementById('injected'));
       });
 
       test('element without explicit template throws', function() {