Fix writing issues (#7749)

* A root component with @DesignRoot must always use its superclass for
default values. Otherwise the written design will be empty as the
design is read in the constructor.

* A component which is not the root must not write its component tree
if the component tree is generated in the constructor. This is a
simplification which should be good enough for most cases (can't add
children in constructor and also using addComponent - in this case
the component added with addComponent will not be written).

* Test cases for nested templates

Change-Id: I3a384d1d8654b9865a3a790ebeb055a300a62135

1 files changed, 1 insertions, 1 deletions

diff --git a/server/src/com/vaadin/ui/Button.java b/server/src/com/vaadin/ui/Button.java
index 9b50b5eebc..7063568f26 100644
--- a/server/src/com/vaadin/ui/Button.java
+++ b/server/src/com/vaadin/ui/Button.java
@@ -727,7 +727,7 @@ public class Button extends AbstractComponent implements
     public void writeDesign(Element design, DesignContext designContext) {
         super.writeDesign(design, designContext);
         Attributes attr = design.attributes();
-        Button def = designContext.getDefaultInstance(this.getClass());
+        Button def = (Button) designContext.getDefaultInstance(this);
         String content = getCaption();
         if (content != null) {
             design.html(content);