plugin api: reload QML plugins without restarting

framework/extensions/iextensionsuiengine.h

@@ -35,5 +35,9 @@ class IExtensionsUiEngine : MODULE_CONTEXT_INTERFACE
 
     virtual QQmlEngine* qmlEngine() const = 0;
     virtual QQmlEngine* qmlEngineApiV1() const = 0;
+
+    //! NOTE Drops what the engines have cached of the plugins on disk, so that
+    //! the next run of a plugin reads it again
+    virtual void clearComponentCache() = 0;
 };
 }

framework/extensions/internal/extensionsprovider.cpp

@@ -38,6 +38,11 @@ static Uri VIEWER_URI = Uri("muse://extensions/viewer");
 
 void ExtensionsProvider::reloadExtensions()
 {
+    //! NOTE Without this, reloading picks up a plugin's manifest but keeps
+    //! running the code the engine compiled the first time, so edits to a
+    //! plugin only take effect after a restart.
+    extensionsUiEngine()->clearComponentCache();
+
     extensionsRegister()->reload();
 }
 

framework/extensions/internal/extensionsprovider.h

@@ -28,6 +28,7 @@
 #include "../iextensionsconfiguration.h"
 #include "../iextensionsregister.h"
 #include "../iextensionsprovider.h"
+#include "../iextensionsuiengine.h"
 #include "interactive/iinteractive.h"
 #include "io/ifilesystem.h"
 
@@ -37,6 +38,7 @@ class ExtensionsProvider : public IExtensionsProvider, public Contextable, publi
     GlobalInject<IExtensionsConfiguration> configuration;
     GlobalInject<IExtensionsRegister> extensionsRegister;
     GlobalInject<io::IFileSystem> fileSystem;
+    ContextInject<IExtensionsUiEngine> extensionsUiEngine = { this };
     ContextInject<IInteractive> interactive = { this };
 
 public:

framework/extensions/internal/extensionsuiengine.cpp

@@ -127,3 +127,18 @@ QQmlEngine* ExtensionsUiEngine::qmlEngineApiV1() const
 {
     return const_cast<ExtensionsUiEngine*>(this)->engineV1();
 }
+
+void ExtensionsUiEngine::clearComponentCache()
+{
+    //! NOTE The engines cache every QML component they have compiled, so a plugin
+    //! edited on disk keeps running its old code until the cache is dropped.
+    //! The engines themselves stay: a plugin window left open was built by one of
+    //! them, and outlives the reload.
+    if (m_engine) {
+        m_engine->clearComponentCache();
+    }
+
+    if (m_engineV1) {
+        m_engineV1->clearComponentCache();
+    }
+}

framework/extensions/internal/extensionsuiengine.h

@@ -49,8 +49,9 @@ class ExtensionsUiEngine : public QObject, public IExtensionsUiEngine, public Co
 
     ~ExtensionsUiEngine();
 
-    QQmlEngine* qmlEngine() const;
-    QQmlEngine* qmlEngineApiV1() const;
+    QQmlEngine* qmlEngine() const override;
+    QQmlEngine* qmlEngineApiV1() const override;
+    void clearComponentCache() override;
 
 private:
 

framework/extensions/qml/Muse/Extensions/extensionslistmodel.cpp

@@ -186,7 +186,9 @@ void ExtensionsListModel::editShortcut(const QString& extensionUri)
 
 void ExtensionsListModel::reloadPlugins()
 {
-    extensionsRegister()->reload();
+    //! NOTE Through the provider: reloading the register alone leaves the QML
+    //! engines holding the code they compiled the first time
+    provider()->reloadExtensions();
 }
 
 void ExtensionsListModel::removeExtension(const QString& uri)

framework/extensions/qml/Muse/Extensions/extensionslistmodel.h

@@ -33,6 +33,7 @@
 #include "interactive/iinteractive.h"
 #include "extensions/iextensioninstaller.h"
 #include "extensions/iextensionsconfiguration.h"
+#include "extensions/iextensionsprovider.h"
 #include "extensions/iextensionsregister.h"
 #include "shortcuts/ishortcutsregister.h"
 
@@ -46,6 +47,7 @@ class ExtensionsListModel : public QAbstractListModel, public QQmlParserStatus,
 
     GlobalInject<IExtensionsConfiguration> configuration;
     GlobalInject<IExtensionsRegister> extensionsRegister;
+    ContextInject<IExtensionsProvider> provider = { this };
     ContextInject<IExtensionInstaller> installer = { this };
     ContextInject<IInteractive> interactive = { this };
     ContextInject<shortcuts::IShortcutsRegister> shortcutsRegister = { this };