Set current instances when calling UI.push from VaadinSession.unlock (#12168)

Change-Id: I27795ab9ae3e3692f508e847936ccaa5a1ebadd4

2 files changed, 16 insertions, 7 deletions

diff --git a/server/src/com/vaadin/server/VaadinSession.java b/server/src/com/vaadin/server/VaadinSession.java
index 504788d479..9dedddcc2c 100644
--- a/server/src/com/vaadin/server/VaadinSession.java
+++ b/server/src/com/vaadin/server/VaadinSession.java
@@ -885,9 +885,9 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
      * Unlocks this session. This method should always be used in a finally
      * block after {@link #lock()} to ensure that the lock is always released.
      * <p>
-     * If {@link #getPushMode() the push mode} is {@link PushMode#AUTOMATIC
-     * automatic}, pushes the changes in all UIs in this session to their
-     * respective clients.
+     * For UIs in this session that have its push mode set to
+     * {@link PushMode#AUTOMATIC automatic}, pending changes will be pushed to
+     * their respective clients.
      * 
      * @see #lock()
      * @see UI#push()
@@ -904,7 +904,13 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
 
                 for (UI ui : getUIs()) {
                     if (ui.getPushConfiguration().getPushMode() == PushMode.AUTOMATIC) {
-                        ui.push();
+                        Map<Class<?>, CurrentInstance> oldCurrent = CurrentInstance
+                                .setCurrent(ui);
+                        try {
+                            ui.push();
+                        } finally {
+                            CurrentInstance.restoreInstances(oldCurrent);
+                        }
                     }
                 }
             }
diff --git a/server/src/com/vaadin/ui/UI.java b/server/src/com/vaadin/ui/UI.java
index 6c9551ea81..403bb31f63 100644
--- a/server/src/com/vaadin/ui/UI.java
+++ b/server/src/com/vaadin/ui/UI.java
@@ -1294,15 +1294,18 @@ public abstract class UI extends AbstractSingleComponentContainer implements
      * Pushes the pending changes and client RPC invocations of this UI to the
      * client-side.
      * <p>
-     * As with all UI methods, it is not safe to call push() without holding the
-     * {@link VaadinSession#lock() session lock}.
+     * As with all UI methods, the session must be locked when calling this
+     * method. It is also recommended that {@link UI#getCurrent()} is set up to
+     * return this UI since writing the response may invoke logic in any
+     * attached component or extension. The recommended way of fulfilling these
+     * conditions is to use {@link #access(Runnable)}.
      * 
      * @throws IllegalStateException
      *             if push is disabled.
      * @throws UIDetachedException
      *             if this UI is not attached to a session.
      * 
-     * @see #getPushMode()
+     * @see #getPushConfiguration()
      * 
      * @since 7.1
      */