fix: workaround Polymer getProperty with mixins/observers (#484)

See Polymer/polymer#5259

src/vaadin-text-field-mixin.html

@@ -806,6 +806,15 @@
       }
     }
 
+    // Workaround for https://github.com/Polymer/polymer/issues/5259
+    get __data() {
+      return this.__dataValue || {};
+    }
+
+    set __data(value) {
+      this.__dataValue = value;
+    }
+
     /**
      * Fired when the user commits a value change.
      *

test/integer-field.html

@@ -19,6 +19,14 @@
     </template>
   </test-fixture>
 
+  <test-fixture id="mixed">
+    <template>
+      <vaadin-integer-field label="integer fld"></vaadin-integer-field>
+      <vaadin-text-field label="text fld"></vaadin-text-field>
+      <vaadin-number-field label="number fld"></vaadin-number-field>
+    </template>
+  </test-fixture>
+
   <script>
     describe('integer-field', () => {
 
@@ -229,6 +237,14 @@
       });
 
     });
+
+    describe('mixed', () => {
+
+      it('should work together with text-field and number-field', () => {
+        expect(() => fixture('mixed')).to.not.throw(Error);
+      });
+
+    });
   </script>
 </body>