introduce PostponedActionsBlocker

Author: rbri

src/main/java/org/htmlunit/html/DomElement.java

@@ -1038,9 +1038,10 @@ public <P extends Page> P click(final boolean shiftKey, final boolean ctrlKey, f
                 mouseDown(shiftKey, ctrlKey, altKey, MouseEvent.BUTTON_LEFT);
             }
 
+            AbstractJavaScriptEngine.PostponedActionsBlocker blocker = null;
             final AbstractJavaScriptEngine<?> jsEngine = webClient.getJavaScriptEngine();
             if (webClient.isJavaScriptEnabled()) {
-                jsEngine.holdPosponedActions();
+                blocker = jsEngine.blockPostponedActions();
             }
             try {
                 if (handleFocus) {
@@ -1090,7 +1091,8 @@ else if (this instanceof HtmlOption) {
                 click(event, shiftKey, ctrlKey, altKey, ignoreVisibility);
             }
             finally {
-                if (webClient.isJavaScriptEnabled()) {
+                if (blocker != null) {
+                    blocker.release();
                     jsEngine.processPostponedActions();
                 }
             }

src/main/java/org/htmlunit/javascript/AbstractJavaScriptEngine.java

@@ -107,8 +107,10 @@ public interface AbstractJavaScriptEngine<SCRIPT> {
     /**
      * <span style="color:red">INTERNAL API - SUBJECT TO CHANGE AT ANY TIME - USE AT YOUR OWN RISK.</span><br>
      * Indicates that no postponed action should be executed.
+     *
+     * @return {@link PostponedActionsBlocker}
      */
-    void holdPosponedActions();
+    PostponedActionsBlocker blockPostponedActions();
 
     /**
      * Compiles the specified JavaScript code in the context of a given scope.
@@ -153,4 +155,10 @@ Object execute(HtmlPage page,
      */
     HtmlUnitContextFactory getContextFactory();
 
+    /**
+     * Helper for blocking the execution of postponed actions for some time.
+     */
+    interface PostponedActionsBlocker {
+        void release();
+    }
 }

src/main/java/org/htmlunit/javascript/JavaScriptEngine.java

@@ -917,8 +917,6 @@ public final Object run(final Context cx) {
     }
 
     private void doProcessPostponedActions() {
-        holdPostponedActions_ = false;
-
         final WebClient webClient = getWebClient();
         if (webClient == null) {
             // shutdown was already called
@@ -1032,11 +1030,16 @@ protected void handleJavaScriptTimeoutError(final HtmlPage page, final TimeoutEr
 
     /**
      * <span style="color:red">INTERNAL API - SUBJECT TO CHANGE AT ANY TIME - USE AT YOUR OWN RISK.</span><br>
-     * Indicates that no postponed action should be executed.
-     */
+    * {@inheritDoc}
+    */
     @Override
-    public void holdPosponedActions() {
+    public PostponedActionsBlocker blockPostponedActions() {
+        if (holdPostponedActions_) {
+            return new LeafPostponedActionsBlocker();
+        }
+
         holdPostponedActions_ = true;
+        return new RootPostponedActionsBlocker(this);
     }
 
     /**
@@ -1385,4 +1388,33 @@ public static String evaluateProxyAutoConfig(final BrowserVersion browserVersion
             return toString(result);
         }
     }
+
+    /**
+     * {@link PostponedActionsBlocker} - the first requested in the current context.
+     */
+    private final class RootPostponedActionsBlocker implements PostponedActionsBlocker {
+        private final JavaScriptEngine jsEngine_;
+
+        private RootPostponedActionsBlocker(final JavaScriptEngine jsEngine) {
+            jsEngine_ = jsEngine;
+        }
+
+        @Override
+        public void release() {
+            jsEngine_.holdPostponedActions_ = false;
+        }
+    }
+
+    /**
+     * {@link PostponedActionsBlocker} - noop blocker.
+     */
+    private final class LeafPostponedActionsBlocker implements PostponedActionsBlocker {
+
+        private LeafPostponedActionsBlocker() {
+        }
+
+        @Override
+        public void release() {
+        }
+    }
 }