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;

 };