Don't clear element content in AbstractComponent.writeDesign (#17488)

WriteDesign now assumes the element it receives is pristine, so elements cannot
be reused without someone else clearing them first. Currently only
DesignContext.createElement directly invokes writeDesign, and it always passes a
new element to it.

Change-Id: Icb777da1d73a28150041914dd9743e7aa0b25e16

2 files changed, 5 insertions, 4 deletions

diff --git a/server/src/com/vaadin/ui/AbstractComponent.java b/server/src/com/vaadin/ui/AbstractComponent.java
index dae073904b..3ceb06b31e 100644
--- a/server/src/com/vaadin/ui/AbstractComponent.java
+++ b/server/src/com/vaadin/ui/AbstractComponent.java
@@ -1239,8 +1239,6 @@ public abstract class AbstractComponent extends AbstractClientConnector
      */
     @Override
     public void writeDesign(Element design, DesignContext designContext) {
-        // clear element contents
-        DesignAttributeHandler.clearElement(design);
         AbstractComponent def = designContext.getDefaultInstance(this);
         Attributes attr = design.attributes();
         // handle default attributes
diff --git a/server/src/com/vaadin/ui/Component.java b/server/src/com/vaadin/ui/Component.java
index adef4b69c5..5db48806c3 100644
--- a/server/src/com/vaadin/ui/Component.java
+++ b/server/src/com/vaadin/ui/Component.java
@@ -747,7 +747,7 @@ public interface Component extends ClientConnector, Sizeable, Serializable {
      * 
      * @since 7.4
      * @param design
-     *            The design as HTML to obtain the state from
+     *            The element to obtain the state from
      * @param designContext
      *            The DesignContext instance used for parsing the design
      */
@@ -763,8 +763,11 @@ public interface Component extends ClientConnector, Sizeable, Serializable {
      * 
      * @since 7.4
      * @param design
-     *            The design as HTML to update with the current state
+     *            The element to write the component state to. Any previous
+     *            attributes or child nodes are <i>not</i> cleared.
      * @param designContext
+     *            The DesignContext instance used for writing the design
+     * 
      */
     public void writeDesign(Element design, DesignContext designContext);