diff -up kdelibs-4.8.90/plasma/package.cpp.libplasma-pk-0002 kdelibs-4.8.90/plasma/package.cpp
--- kdelibs-4.8.90/plasma/package.cpp.libplasma-pk-0002	2012-06-05 10:47:01.000000000 +0200
+++ kdelibs-4.8.90/plasma/package.cpp	2012-06-08 15:40:14.219728253 +0200
@@ -43,8 +43,11 @@
 #include <kdebug.h>
 
 #include "authorizationmanager.h"
+#include "dataenginemanager.h"
 #include "packagemetadata.h"
+#include "scripting/scriptengine.h"
 #include "private/authorizationmanager_p.h"
+#include "private/componentinstaller_p.h"
 #include "private/package_p.h"
 #include "private/plasmoidservice_p.h"
 #include "private/service_p.h"
@@ -580,6 +583,41 @@ bool Package::installPackage(const QStri
         // no need to remove the temp dir (which has been successfully moved if it's an archive)
         tempdir.setAutoRemove(false);
     }
+    // check for missing dependencies
+    QString requiredScriptEngine = meta.implementationApi();
+    if (!requiredScriptEngine.isEmpty()) {
+        // figure out the component type to query for
+        ComponentTypes componentTypes = static_cast<ComponentTypes>(0);
+        QStringList serviceTypes = meta.serviceType().split(',');
+        if (serviceTypes.contains("Plasma/Applet")) {
+            componentTypes |= AppletComponent;
+        }
+        if (serviceTypes.contains("Plasma/DataEngine")) {
+            componentTypes |= DataEngineComponent;
+        }
+        if (serviceTypes.contains("Plasma/Runner")) {
+            componentTypes |= RunnerComponent;
+        }
+        if (serviceTypes.contains("Plasma/Wallpaper")) {
+            componentTypes |= WallpaperComponent;
+        }
+        if (!knownLanguages(componentTypes).contains(requiredScriptEngine)) {
+            // install the missing script engine
+            // force prompting because the user has just explicitly installed a widget
+            ComponentInstaller::self()->installMissingComponent("scriptengine", requiredScriptEngine, 0, true);
+        }
+    }
+    QStringList requiredDataEngines = meta.requiredDataEngines();
+    if (!requiredDataEngines.isEmpty()) {
+        QStringList knownDataEngines = DataEngineManager::self()->listAllEngines(meta.application());
+        foreach (const QString &requiredDataEngine, requiredDataEngines) {
+            if (!knownDataEngines.contains(requiredDataEngine)) {
+                // install the missing data engine
+                // force prompting because the user has just explicitly installed a widget
+                ComponentInstaller::self()->installMissingComponent("dataengine", requiredDataEngine, 0, true);
+            }
+        }
+    }
 
     if (!servicePrefix.isEmpty()) {
         // and now we register it as a service =)
diff -up kdelibs-4.8.90/plasma/packagemetadata.cpp.libplasma-pk-0002 kdelibs-4.8.90/plasma/packagemetadata.cpp
--- kdelibs-4.8.90/plasma/packagemetadata.cpp.libplasma-pk-0002	2012-05-23 01:45:26.000000000 +0200
+++ kdelibs-4.8.90/plasma/packagemetadata.cpp	2012-06-08 15:24:24.439149182 +0200
@@ -52,6 +52,7 @@ class PackageMetadataPrivate
         QString serviceType;
         QString api;
         KUrl location;
+        QStringList requiredDataEngines;
 };
 
 PackageMetadata::PackageMetadata(const PackageMetadata &other)
@@ -108,6 +109,7 @@ void PackageMetadata::write(const QStrin
     config.writeEntry("X-KDE-ParentApp", d->app);
     config.writeEntry("Type", d->type);
     config.writeEntry("X-Plasma-RemoteLocation", d->location);
+    config.writeEntry("X-Plasma-RequiredDataEngines", d->requiredDataEngines);
 }
 
 void PackageMetadata::read(const QString &filename)
@@ -154,6 +156,7 @@ void PackageMetadata::read(const QString
     d->app = config.readEntry("X-KDE-ParentApp", d->app);
     d->type = config.readEntry("Type", d->type);
     d->location = config.readEntry("X-Plasma-RemoteLocation", d->location);
+    d->requiredDataEngines = config.readEntry("X-Plasma-RequiredDataEngines", d->requiredDataEngines);
 }
 
 QString PackageMetadata::name() const
@@ -246,6 +249,11 @@ QString PackageMetadata::implementationA
     return d->api;
 }
 
+QStringList PackageMetadata::requiredDataEngines() const
+{
+    return d->requiredDataEngines;
+}
+
 void PackageMetadata::setImplementationApi(const QString &api)
 {
     d->api = api;
@@ -321,6 +329,11 @@ void PackageMetadata::setRemoteLocation(
     d->location = location;
 }
 
+void PackageMetadata::setRequiredDataEngines(const QStringList &requiredDataEngines)
+{
+    d->requiredDataEngines = requiredDataEngines;
+}
+
 void PackageMetadata::setType(const QString &type)
 {
     d->type = type;
diff -up kdelibs-4.8.90/plasma/packagemetadata.h.libplasma-pk-0002 kdelibs-4.8.90/plasma/packagemetadata.h
--- kdelibs-4.8.90/plasma/packagemetadata.h.libplasma-pk-0002	2012-05-23 01:45:26.000000000 +0200
+++ kdelibs-4.8.90/plasma/packagemetadata.h	2012-06-08 15:24:24.481149665 +0200
@@ -21,6 +21,7 @@
 #define PLASMA_PACKAGEMETADATA_H
 
 #include <QtCore/QString>
+#include <QtCore/QStringList>
 
 #include <plasma/plasma_export.h>
 
@@ -92,6 +93,7 @@ public:
     QString pluginName() const;
     QString implementationApi() const;
     KUrl remoteLocation() const;
+    QStringList requiredDataEngines() const;
 
     QString type() const;
 
@@ -205,6 +207,11 @@ public:
      */
     void setImplementationApi(const QString &api);
 
+    /**
+     * Set the required data engines for this package.
+     */
+    void setRequiredDataEngines(const QStringList &);
+
 private:
     PackageMetadataPrivate * const d;
 };