Allow to add a dependency dynamically via JS expression

flow-client/eclipse/GWT tests.launch

@@ -25,5 +25,5 @@
 <stringAttribute key="org.eclipse.jdt.launching.MAIN_TYPE" value="com.vaadin.client.GwtSuite"/>
 <stringAttribute key="org.eclipse.jdt.launching.PROJECT_ATTR" value="flow-client"/>
 <stringAttribute key="org.eclipse.jdt.launching.SOURCE_PATH_PROVIDER" value="org.eclipse.m2e.launchconfig.sourcepathProvider"/>
-<stringAttribute key="org.eclipse.jdt.launching.VM_ARGUMENTS" value="-Dgwt.args=&quot;-war target/www-test -logLevel INFO -prod -ea -sourceLevel 1.8 -runStyle HtmlUnit:FF38 -style PRETTY&quot;"/>
+<stringAttribute key="org.eclipse.jdt.launching.VM_ARGUMENTS" value="-Dgwt.args=&quot;-war target/www-test -logLevel INFO -prod -ea -sourceLevel 1.8 -runStyle HtmlUnit:FF38 -style PRETTY&quot; -Dvaadin.enableDevServer=false"/>
 </launchConfiguration>

flow-client/src/main/java/com/vaadin/client/DependencyLoader.java

@@ -18,13 +18,15 @@
 import java.util.function.BiConsumer;
 
 import com.google.gwt.core.client.Scheduler;
+
 import com.vaadin.client.ResourceLoader.ResourceLoadEvent;
 import com.vaadin.client.ResourceLoader.ResourceLoadListener;
 import com.vaadin.client.flow.collection.JsArray;
 import com.vaadin.client.flow.collection.JsCollections;
 import com.vaadin.client.flow.collection.JsMap;
 import com.vaadin.flow.shared.ui.Dependency;
 import com.vaadin.flow.shared.ui.LoadMode;
+
 import elemental.json.JsonArray;
 import elemental.json.JsonObject;
 
@@ -47,7 +49,8 @@ public void onLoad(ResourceLoadEvent event) {
 
         @Override
         public void onError(ResourceLoadEvent event) {
-            Console.error(event.getResourceUrl() + " could not be loaded.");
+            Console.error(
+                    "'" + event.getResourceData() + "' could not be loaded.");
             // The show must go on
             onLoad(event);
         }
@@ -61,7 +64,7 @@ public void onLoad(ResourceLoadEvent event) {
 
         @Override
         public void onError(ResourceLoadEvent event) {
-            Console.error(event.getResourceUrl() + " could not be loaded.");
+            Console.error(event.getResourceData() + " could not be loaded.");
             // The show must go on
             onLoad(event);
         }
@@ -81,21 +84,15 @@ public DependencyLoader(Registry registry) {
         this.registry = registry;
     }
 
-    private void inlineDependency(String dependencyContents,
+    private void loadLazyDependency(String dependencyUrl,
             final BiConsumer<String, ResourceLoadListener> loader) {
-        startEagerDependencyLoading();
-        loader.accept(dependencyContents, EAGER_RESOURCE_LOAD_LISTENER);
+        loader.accept(dependencyUrl, LAZY_RESOURCE_LOAD_LISTENER);
     }
 
-    private void loadEagerDependency(String dependencyUrl,
+    private void loadDependencyEagerly(String data,
             final BiConsumer<String, ResourceLoadListener> loader) {
         startEagerDependencyLoading();
-        loader.accept(dependencyUrl, EAGER_RESOURCE_LOAD_LISTENER);
-    }
-
-    private void loadLazyDependency(String dependencyUrl,
-            final BiConsumer<String, ResourceLoadListener> loader) {
-        loader.accept(dependencyUrl, LAZY_RESOURCE_LOAD_LISTENER);
+        loader.accept(data, EAGER_RESOURCE_LOAD_LISTENER);
     }
 
     /**
@@ -188,28 +185,34 @@ private JsMap<String, BiConsumer<String, ResourceLoadListener>> extractLazyDepen
                 .map();
         for (int i = 0; i < dependencies.length(); i++) {
             JsonObject dependencyJson = dependencies.getObject(i);
+            Dependency.Type type = Dependency.Type
+                    .valueOf(dependencyJson.getString(Dependency.KEY_TYPE));
             BiConsumer<String, ResourceLoadListener> resourceLoader = getResourceLoader(
-                    Dependency.Type.valueOf(
-                            dependencyJson.getString(Dependency.KEY_TYPE)),
-                    loadMode);
+                    type, loadMode);
 
-            switch (loadMode) {
-            case EAGER:
-                loadEagerDependency(getDependencyUrl(dependencyJson),
-                        resourceLoader);
-                break;
-            case LAZY:
-                lazyDependencies.set(getDependencyUrl(dependencyJson),
+            if (type == Dependency.Type.DYNAMIC_IMPORT) {
+                loadDependencyEagerly(
+                        dependencyJson.getString(Dependency.KEY_URL),
                         resourceLoader);
-                break;
-            case INLINE:
-                inlineDependency(
-                        dependencyJson.getString(Dependency.KEY_CONTENTS),
-                        resourceLoader);
-                break;
-            default:
-                throw new IllegalArgumentException(
-                        "Unknown load mode = " + loadMode);
+            } else {
+                switch (loadMode) {
+                case EAGER:
+                    loadDependencyEagerly(getDependencyUrl(dependencyJson),
+                            resourceLoader);
+                    break;
+                case LAZY:
+                    lazyDependencies.set(getDependencyUrl(dependencyJson),
+                            resourceLoader);
+                    break;
+                case INLINE:
+                    loadDependencyEagerly(
+                            dependencyJson.getString(Dependency.KEY_CONTENTS),
+                            resourceLoader);
+                    break;
+                default:
+                    throw new IllegalArgumentException(
+                            "Unknown load mode = " + loadMode);
+                }
             }
         }
         return lazyDependencies;
@@ -250,6 +253,8 @@ private BiConsumer<String, ResourceLoadListener> getResourceLoader(
             }
             return (scriptUrl, resourceLoadListener) -> resourceLoader
                     .loadJsModule(scriptUrl, resourceLoadListener, false, true);
+        case DYNAMIC_IMPORT:
+            return resourceLoader::loadDynamicImport;
         default:
             throw new IllegalArgumentException(
                     "Unknown dependency type " + resourceType);

flow-client/src/main/java/com/vaadin/client/ResourceLoader.java

@@ -16,15 +16,20 @@
 
 package com.vaadin.client;
 
+import java.util.function.Supplier;
+
 import com.google.gwt.core.client.Duration;
 import com.google.gwt.core.client.GWT;
 import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.core.client.Scheduler.RepeatingCommand;
 import com.google.gwt.user.client.Timer;
+
 import com.vaadin.client.flow.collection.JsArray;
 import com.vaadin.client.flow.collection.JsCollections;
 import com.vaadin.client.flow.collection.JsMap;
 import com.vaadin.client.flow.collection.JsSet;
+import com.vaadin.client.flow.util.NativeFunction;
+
 import elemental.client.Browser;
 import elemental.dom.Document;
 import elemental.dom.Element;
@@ -127,19 +132,20 @@ public void onError(ResourceLoadEvent event) {
      */
     public static class ResourceLoadEvent {
         private final ResourceLoader loader;
-        private final String resourceUrl;
+        private final String resourceData;
 
         /**
          * Creates a new event.
          *
          * @param loader
          *            the resource loader that has loaded the resource
-         * @param resourceUrl
-         *            the url of the loaded resource
+         * @param resourceData
+         *            the url or content of the loaded resource or the JS
+         *            expression that imports the resource
          */
-        public ResourceLoadEvent(ResourceLoader loader, String resourceUrl) {
+        public ResourceLoadEvent(ResourceLoader loader, String resourceData) {
             this.loader = loader;
-            this.resourceUrl = resourceUrl;
+            this.resourceData = resourceData;
         }
 
         /**
@@ -152,12 +158,14 @@ public ResourceLoader getResourceLoader() {
         }
 
         /**
-         * Gets the absolute url of the loaded resource.
+         * Gets the absolute url or content of the loaded resource or the JS
+         * expression that imports the resource.
          *
-         * @return the absolute url of the loaded resource
+         * @return the absolute url or content of the loaded resource or the JS
+         *         expression that imports the resource
          */
-        public String getResourceUrl() {
-            return resourceUrl;
+        public String getResourceData() {
+            return resourceData;
         }
 
     }
@@ -356,7 +364,7 @@ private void loadScript(String scriptUrl,
      *            listener to notify when script is loaded
      */
     public void inlineScript(String scriptContents,
-                             final ResourceLoadListener resourceLoadListener) {
+            final ResourceLoadListener resourceLoadListener) {
         ResourceLoadEvent event = new ResourceLoadEvent(this, scriptContents);
         if (loadedResources.has(scriptContents)) {
             if (resourceLoadListener != null) {
@@ -635,6 +643,25 @@ public void inlineStyleSheet(String styleSheetContents,
         }
     }
 
+    /**
+     * Loads a dynamic import via the provided JS {@code expression} and reports
+     * the result via the {@code resourceLoadListener}.
+     *
+     * @param expression
+     *            the JS expression which returns a Promise
+     * @param resourceLoadListener
+     *            a listener to report the Promise result exection
+     */
+    public void loadDynamicImport(String expression,
+            ResourceLoadListener resourceLoadListener) {
+
+        ResourceLoadEvent event = new ResourceLoadEvent(this, expression);
+        NativeFunction function = new NativeFunction(expression);
+        runPromiseExpression(expression, () -> function.call(null),
+                () -> resourceLoadListener.onLoad(event),
+                () -> resourceLoadListener.onError(event));
+    }
+
     private void addCssLoadHandler(String styleSheetContents,
             ResourceLoadEvent event, StyleElement styleSheetElement) {
         if (BrowserInfo.get().isSafariOrIOS() || BrowserInfo.get().isOpera()) {
@@ -707,8 +734,8 @@ private static boolean addListener(String resourceId,
 
     private void fireError(ResourceLoadEvent event) {
         registry.getSystemErrorHandler()
-                .handleError("Error loading " + event.getResourceUrl());
-        String resource = event.getResourceUrl();
+                .handleError("Error loading " + event.getResourceData());
+        String resource = event.getResourceData();
 
         JsArray<ResourceLoadListener> listeners = loadListeners.get(resource);
         loadListeners.delete(resource);
@@ -723,8 +750,8 @@ private void fireError(ResourceLoadEvent event) {
     }
 
     private void fireLoad(ResourceLoadEvent event) {
-        Console.log("Loaded " + event.getResourceUrl());
-        String resource = event.getResourceUrl();
+        Console.log("Loaded " + event.getResourceData());
+        String resource = event.getResourceData();
         JsArray<ResourceLoadListener> listeners = loadListeners.get(resource);
         loadedResources.add(resource);
         loadListeners.delete(resource);
@@ -737,4 +764,22 @@ private void fireLoad(ResourceLoadEvent event) {
             }
         }
     }
+
+    private static native void runPromiseExpression(String expression,
+            Supplier<Object> promiseSupplier, Runnable onSuccess,
+            Runnable onError)
+    /*-{
+          try {
+            var promise = [email protected]::get(*)();
+            if ( !(promise instanceof Promise )){
+                throw new Error('The expression "'+expression+'" result is not a Promise.');
+            }
+            promise.then( function(result) { [email protected]::run(*)(); } ,
+                          function(error) { [email protected]::run(*)(); } );
+          }
+          catch(error) {
+               [email protected]::run(*)();
+          }
+    }-*/;
+
 }

flow-client/src/main/java/com/vaadin/client/communication/AtmospherePushConnection.java

@@ -743,7 +743,7 @@ public void onLoad(ResourceLoadEvent event) {
                 @Override
                 public void onError(ResourceLoadEvent event) {
                     getConnectionStateHandler()
-                            .pushScriptLoadError(event.getResourceUrl());
+                            .pushScriptLoadError(event.getResourceData());
 
                 }
             };