Allow plugin loading from external directory (#3364)

* Load custom plugin directories

* Allow plugins to be loaded from an external directory

* Handle exception when path is not relative to base path

* Fix typo

* Use pathlib

* Move plugin directory code into registry.py

- Allows us to reload plugins without having to reload the server itself

Co-authored-by: Matthias Mair <code@mjmair.com>

InvenTree/InvenTree/settings.py

@@ -935,17 +935,6 @@ PLUGINS_ENABLED = _is_true(get_setting(
 
 PLUGIN_FILE = get_plugin_file()
 
-# Plugin Directories (local plugins will be loaded from these directories)
-PLUGIN_DIRS = ['plugin.builtin', ]
-
-if not TESTING:
-    # load local deploy directory in prod
-    PLUGIN_DIRS.append('plugins')  # pragma: no cover
-
-if DEBUG or TESTING:
-    # load samples in debug mode
-    PLUGIN_DIRS.append('plugin.samples')
-
 # Plugin test settings
 PLUGIN_TESTING = get_setting('PLUGIN_TESTING', TESTING)  # are plugins beeing tested?
 PLUGIN_TESTING_SETUP = get_setting('PLUGIN_TESTING_SETUP', False)  # load plugins from setup hooks in testing?

InvenTree/plugin/helpers.py

@@ -172,10 +172,16 @@ class GitStatus:
 
 
 # region plugin finders
-def get_modules(pkg):
+def get_modules(pkg, path=None):
     """Get all modules in a package."""
     context = {}
-    for loader, name, _ in pkgutil.walk_packages(pkg.__path__):
+
+    if path is None:
+        path = pkg.__path__
+    elif type(path) is not list:
+        path = [path]
+
+    for loader, name, _ in pkgutil.walk_packages(path):
         try:
             module = loader.find_module(name).load_module(name)
             pkg_names = getattr(module, '__all__', None)
@@ -199,7 +205,7 @@ def get_classes(module):
     return inspect.getmembers(module, inspect.isclass)
 
 
-def get_plugins(pkg, baseclass):
+def get_plugins(pkg, baseclass, path=None):
     """Return a list of all modules under a given package.
 
     - Modules must be a subclass of the provided 'baseclass'
@@ -207,7 +213,7 @@ def get_plugins(pkg, baseclass):
     """
     plugins = []
 
-    modules = get_modules(pkg)
+    modules = get_modules(pkg, path=path)
 
     # Iterate through each module in the package
     for mod in modules:

InvenTree/plugin/plugin.py

@@ -275,7 +275,11 @@ class InvenTreePlugin(MixinBase, MetaBase):
         """Path to the plugin."""
         if self._is_package:
             return self.__module__  # pragma: no cover
-        return pathlib.Path(self.def_path).relative_to(settings.BASE_DIR)
+
+        try:
+            return pathlib.Path(self.def_path).relative_to(settings.BASE_DIR)
+        except ValueError:
+            return pathlib.Path(self.def_path)
 
     @property
     def settings_url(self):

InvenTree/plugin/registry.py

@@ -187,6 +187,53 @@ class PluginsRegistry:
 
         logger.info('Finished reloading plugins')
 
+    def plugin_dirs(self):
+        """Construct a list of directories from where plugins can be loaded"""
+
+        dirs = ['plugin.builtin', ]
+
+        if settings.TESTING or settings.DEBUG:
+            # If in TEST or DEBUG mode, load plugins from the 'samples' directory
+            dirs.append('plugin.samples')
+
+        if settings.TESTING:
+            custom_dirs = os.getenv('INVENTREE_PLUGIN_TEST_DIR', None)
+        else:
+            custom_dirs = os.getenv('INVENTREE_PLUGIN_DIR', None)
+
+            # Load from user specified directories (unless in testing mode)
+            dirs.append('plugins')
+
+        if custom_dirs is not None:
+            # Allow multiple plugin directories to be specified
+            for pd_text in custom_dirs.split(','):
+                pd = pathlib.Path(pd_text.strip()).absolute()
+
+                # Attempt to create the directory if it does not already exist
+                if not pd.exists():
+                    try:
+                        pd.mkdir(exist_ok=True)
+                    except Exception:
+                        logger.error(f"Could not create plugin directory '{pd}'")
+                        continue
+
+                # Ensure the directory has an __init__.py file
+                init_filename = pd.joinpath('__init__.py')
+
+                if not init_filename.exists():
+                    try:
+                        init_filename.write_text("# InvenTree plugin directory\n")
+                    except Exception:
+                        logger.error(f"Could not create file '{init_filename}'")
+                        continue
+
+                if pd.exists() and pd.is_dir():
+                    # By this point, we have confirmed that the directory at least exists
+                    logger.info(f"Added plugin directory: '{pd}'")
+                    dirs.append(pd)
+
+        return dirs
+
     def collect_plugins(self):
         """Collect plugins from all possible ways of loading."""
         if not settings.PLUGINS_ENABLED:
@@ -196,8 +243,21 @@ class PluginsRegistry:
         self.plugin_modules = []  # clear
 
         # Collect plugins from paths
-        for plugin in settings.PLUGIN_DIRS:
-            modules = get_plugins(importlib.import_module(plugin), InvenTreePlugin)
+        for plugin in self.plugin_dirs():
+
+            print(f"Loading plugins from directory '{plugin}'")
+
+            parent_path = None
+            parent_obj = pathlib.Path(plugin)
+
+            # If a "path" is provided, some special handling is required
+            if parent_obj.name is not plugin and len(parent_obj.parts) > 1:
+                print("loading from a qualified path:", plugin)
+                parent_path = parent_obj.parent
+                plugin = parent_obj.name
+
+            modules = get_plugins(importlib.import_module(plugin), InvenTreePlugin, path=parent_path)
+
             if modules:
                 [self.plugin_modules.append(item) for item in modules]