Append plugins dir to pythonpath

src/backend/InvenTree/plugin/apps.py

@@ -5,11 +5,15 @@ The main code for plugin special sauce is in the plugin registry in `InvenTree/p
 """
 
 import logging
+import pathlib
+import sys
 
 from django.apps import AppConfig
+from django.conf import settings
 
 from maintenance_mode.core import set_maintenance_mode
 
+from InvenTree.config import get_plugin_dir
 from InvenTree.ready import canAppAccessDatabase, isInMainThread, isInWorkerThread
 from plugin import registry
 
@@ -23,7 +27,7 @@ class PluginAppConfig(AppConfig):
 
     def ready(self):
         """The ready method is extended to initialize plugins."""
-        # skip loading if we run in a background thread
+        self.update_python_path()
 
         if not isInMainThread() and not isInWorkerThread():
             return
@@ -56,3 +60,29 @@ class PluginAppConfig(AppConfig):
                 # drop out of maintenance
                 # makes sure we did not have an error in reloading and maintenance is still active
                 set_maintenance_mode(False)
+
+    def update_python_path(self):
+        """Update the PYTHONPATH to include the plugin directory."""
+        if not settings.PLUGINS_ENABLED:
+            # Custom plugins disabled - no need to update PYTHONPATH
+            logger.info('Custom plugins are not enabled')
+            return
+
+        plugin_dir = get_plugin_dir()
+
+        if not plugin_dir:
+            logger.warning('Plugins directory not specified')
+            return
+
+        if plugin_dir := get_plugin_dir():
+            path = pathlib.Path(plugin_dir)
+
+            if not path.exists():
+                try:
+                    path.mkdir(parents=True, exist_ok=True)
+                except Exception:
+                    logger.error(f'Failed to create plugin directory: {plugin_dir}')
+                    return
+
+            if plugin_dir not in sys.path:
+                sys.path.append(plugin_dir)