Fix some issues with reloading of action plugins

First issue: the C++ action plugins list should be cleared so that any
plugins that fail to reload do not hang around on the toolbar.
This is fixed on the C++ side.

Second issue: inner dependencies of plugins that are modules were not
reloaded before, which broke reloading for many plugin examples out there.
This is fixed on the Python side by keeping track of dependencies and
clearing them out before reloading a module (unfortunately there doesn't
seem to be a way to do this in the standard library)

Fixes https://gitlab.com/kicad/code/kicad/-/issues/7245

pcbnew/action_plugin.cpp

@@ -204,3 +204,12 @@ void ACTION_PLUGINS::SetActionRunning( bool aRunning )
 {
     ACTION_PLUGINS::m_actionRunning = aRunning;
 }
+
+
+void ACTION_PLUGINS::UnloadAll()
+{
+    for( ACTION_PLUGIN* plugin : m_actionsList )
+        delete plugin;
+
+    m_actionsList.clear();
+}

pcbnew/action_plugin.h

@@ -218,6 +218,11 @@ public:
      * @param aRunning sets whether an action is running now.
      */
     static void SetActionRunning( bool aRunning );
+
+    /**
+     * Unloads (deregisters) all action plugins
+     */
+    static void UnloadAll();
 };
 
 #endif /* PCBNEW_ACTION_PLUGINS_H */

pcbnew/pcb_edit_frame.cpp

@@ -98,6 +98,9 @@
 
 #if defined(KICAD_SCRIPTING) || defined(KICAD_SCRIPTING_WXPYTHON)
 #include <python_scripting.h>
+#if defined(KICAD_SCRIPTING_ACTION_MENU)
+#include <action_plugin.h>
+#endif
 #endif
 
 
@@ -1487,6 +1490,11 @@ void PCB_EDIT_FRAME::PythonPluginsReload()
 {
     // Reload Python plugins if they are newer than the already loaded, and load new plugins
 #if defined(KICAD_SCRIPTING)
+#if defined(KICAD_SCRIPTING_ACTION_MENU)
+    // Remove all action plugins so that we don't keep references to old versions
+    ACTION_PLUGINS::UnloadAll();
+#endif
+
     // Reload plugin list: reload Python plugins if they are newer than the already loaded,
     // and load new plugins
     PythonPluginsReloadBase();

scripting/kicadplugins.i

@@ -96,28 +96,33 @@ def LoadPluginModule(Dirname, ModuleName, FileName):
     import sys
     import traceback
 
+    try:
+        from importlib import reload # Python 3.4 or above
+    except ImportError:
+        from imp import reload # Python <3.4; harmless alias on 2.7
+
     global NOT_LOADED_WIZARDS
     global FULL_BACK_TRACE
+    global KICAD_PLUGINS
+
+    top_level_modules = KICAD_PLUGINS.keys()
 
     try:  # If there is an error loading the script, skip it
 
         module_filename = os.path.join( Dirname, FileName )
         mtime = os.path.getmtime( module_filename )
+        mods_before = set( sys.modules )
 
         if ModuleName in KICAD_PLUGINS:
             plugin = KICAD_PLUGINS[ModuleName]
 
-            if sys.version_info >= (3,4,0):
-                import importlib
-                mod = importlib.reload( plugin["ModuleName"] )
-            elif sys.version_info >= (3,2,0):
-                """
-                TODO: This branch can be removed once the required python version is >=3.4
-                """
-                import imp
-                mod = imp.reload( plugin["ModuleName"] )
-            else:
-                mod = reload( plugin["ModuleName"] )
+            for dependency in plugin["dependencies"]:
+                if dependency in sys.modules and dependency not in top_level_modules:
+                    del sys.modules[dependency]
+
+            mods_before = set( sys.modules )
+
+            mod = reload( plugin["ModuleName"] )
 
         else:
             if sys.version_info >= (3,0,0):
@@ -126,11 +131,17 @@ def LoadPluginModule(Dirname, ModuleName, FileName):
             else:
                 mod = __import__( ModuleName, locals(), globals() )
 
+        mods_after = set( sys.modules ).difference( mods_before )
+
         KICAD_PLUGINS[ModuleName]={ "filename":module_filename,
                                     "modification_time":mtime,
-                                    "ModuleName":mod }
+                                    "ModuleName":mod,
+                                    "dependencies": mods_after }
 
     except:
+        if ModuleName in KICAD_PLUGINS:
+            del KICAD_PLUGINS[ModuleName]
+
         if NOT_LOADED_WIZARDS != "" :
             NOT_LOADED_WIZARDS += "\n"
         NOT_LOADED_WIZARDS += module_filename