ExtensionSystem: Add a less verbose way to *Plugin::initialize()

Barely any of our plugins use the arguments or report error on
initialization.

Use it to the Nim plugin for demonstration purposes.

Change-Id: I0aead51afff61648fe03ad7e1ef7b4100abd9ed6
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/extensionsystem/iplugin.cpp

@@ -58,6 +58,17 @@
     \sa delayedInitialize()
 */
 
+/*!
+    \fn void ExtensionSystem::IPlugin::initialize()
+    This function is called as the default implementation of
+    \c initialize(const QStringList &arguments, QString *errorString) and can be
+    overwritten instead of the full-args version in cases the parameters
+    are not used by the implementation and there is no error to report.
+
+    \sa extensionsInitialized()
+    \sa delayedInitialize()
+*/
+
 /*!
     \fn void ExtensionSystem::IPlugin::extensionsInitialized()
     Called after the initialize() function has been called,
@@ -167,6 +178,14 @@ IPlugin::~IPlugin()
     d = nullptr;
 }
 
+bool IPlugin::initialize(const QStringList &arguments, QString *errorString)
+{
+    Q_UNUSED(arguments)
+    Q_UNUSED(errorString)
+    initialize();
+    return true;
+}
+
 /*!
     Returns objects that are meant to be passed on to \l QTest::qExec().
 

src/libs/extensionsystem/iplugin.h

@@ -30,7 +30,8 @@ public:
     IPlugin();
     ~IPlugin() override;
 
-    virtual bool initialize(const QStringList &arguments, QString *errorString) = 0;
+    virtual bool initialize(const QStringList &arguments, QString *errorString);
+    virtual void initialize() {}
     virtual void extensionsInitialized() {}
     virtual bool delayedInitialize() { return false; }
     virtual ShutdownFlag aboutToShutdown() { return SynchronousShutdown; }

src/plugins/nim/nimplugin.cpp

@@ -73,11 +73,8 @@ NimPlugin::~NimPlugin()
     delete d;
 }
 
-bool NimPlugin::initialize(const QStringList &arguments, QString *errorMessage)
+void NimPlugin::initialize()
 {
-    Q_UNUSED(arguments)
-    Q_UNUSED(errorMessage)
-
     d = new NimPluginPrivate;
 
     ToolChainManager::registerLanguage(Constants::C_NIMLANGUAGE_ID, Constants::C_NIMLANGUAGE_NAME);
@@ -88,8 +85,6 @@ bool NimPlugin::initialize(const QStringList &arguments, QString *errorMessage)
 
     ProjectManager::registerProjectType<NimProject>(Constants::C_NIM_PROJECT_MIMETYPE);
     ProjectManager::registerProjectType<NimbleProject>(Constants::C_NIMBLE_MIMETYPE);
-
-    return true;
 }
 
 void NimPlugin::extensionsInitialized()

src/plugins/nim/nimplugin.h

@@ -16,7 +16,7 @@ public:
     NimPlugin() = default;
     ~NimPlugin() final;
 
-    bool initialize(const QStringList &arguments, QString *errorMessage) final;
+    void initialize() final;
     void extensionsInitialized() final;
 
 #ifdef WITH_TESTS