Improve plugin testing (#3517)

* refactor entrypoint into helpers

* Add lookup by metadata
This is geared towards plugins packaged in pkgs that differ in name from their top module

* Make module lookup predictable in changing pkg-envs

* remove no coverage from plugin packages

* ignore coverage for production loadin

* refactor plugin collection - move assigment out

* do not cover fs errors

* test custom dir loading

* test module meta fetcher

* add a bit more safety

* do not cover sanity checkers

* add folder loading test

* ignore again for cleaner diffs for now

* ignore safety catch

* rename test

* Add test for package installs

* fix docstring name

* depreciate test for now

* Fix for out of BASE_DIR paths

* ignore catch

* remove unneeded complexity

* add testing for outside folders

* more docstrings and simpler methods

* make call simpler

InvenTree/plugin/registry.py

@@ -4,6 +4,7 @@
 - Manages setup and teardown of plugin class instances
 """
 
+import imp
 import importlib
 import logging
 import os
@@ -200,7 +201,7 @@ class PluginsRegistry:
 
         if settings.TESTING:
             custom_dirs = os.getenv('INVENTREE_PLUGIN_TEST_DIR', None)
-        else:
+        else:  # pragma: no cover
             custom_dirs = get_setting('INVENTREE_PLUGIN_DIR', 'plugin_dir')
 
             # Load from user specified directories (unless in testing mode)
@@ -215,7 +216,7 @@ class PluginsRegistry:
                 if not pd.exists():
                     try:
                         pd.mkdir(exist_ok=True)
-                    except Exception:
+                    except Exception:  # pragma: no cover
                         logger.error(f"Could not create plugin directory '{pd}'")
                         continue
 
@@ -225,24 +226,31 @@ class PluginsRegistry:
                 if not init_filename.exists():
                     try:
                         init_filename.write_text("# InvenTree plugin directory\n")
-                    except Exception:
+                    except Exception:  # pragma: no cover
                         logger.error(f"Could not create file '{init_filename}'")
                         continue
 
+                # By this point, we have confirmed that the directory at least exists
                 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)
+                    # Convert to python dot-path
+                    if pd.is_relative_to(settings.BASE_DIR):
+                        pd_path = '.'.join(pd.relative_to(settings.BASE_DIR).parts)
+                    else:
+                        pd_path = str(pd)
+
+                    # Add path
+                    dirs.append(pd_path)
+                    logger.info(f"Added plugin directory: '{pd}' as '{pd_path}'")
 
         return dirs
 
     def collect_plugins(self):
-        """Collect plugins from all possible ways of loading."""
+        """Collect plugins from all possible ways of loading. Returned as list."""
         if not settings.PLUGINS_ENABLED:
             # Plugins not enabled, do nothing
             return  # pragma: no cover
 
-        self.plugin_modules = []  # clear
+        collected_plugins = []
 
         # Collect plugins from paths
         for plugin in self.plugin_dirs():
@@ -258,26 +266,33 @@ class PluginsRegistry:
                 parent_path = str(parent_obj.parent)
                 plugin = parent_obj.name
 
-            modules = get_plugins(importlib.import_module(plugin), InvenTreePlugin, path=parent_path)
+            # Gather Modules
+            if parent_path:
+                raw_module = imp.load_source(plugin, str(parent_obj.joinpath('__init__.py')))
+            else:
+                raw_module = importlib.import_module(plugin)
+            modules = get_plugins(raw_module, InvenTreePlugin, path=parent_path)
 
             if modules:
-                [self.plugin_modules.append(item) for item in modules]
+                [collected_plugins.append(item) for item in modules]
 
         # Check if not running in testing mode and apps should be loaded from hooks
         if (not settings.PLUGIN_TESTING) or (settings.PLUGIN_TESTING and settings.PLUGIN_TESTING_SETUP):
             # Collect plugins from setup entry points
-            for entry in get_entrypoints():  # pragma: no cover
+            for entry in get_entrypoints():
                 try:
                     plugin = entry.load()
                     plugin.is_package = True
                     plugin._get_package_metadata()
-                    self.plugin_modules.append(plugin)
-                except Exception as error:
+                    collected_plugins.append(plugin)
+                except Exception as error:  # pragma: no cover
                     handle_error(error, do_raise=False, log_name='discovery')
 
         # Log collected plugins
-        logger.info(f'Collected {len(self.plugin_modules)} plugins!')
-        logger.info(", ".join([a.__module__ for a in self.plugin_modules]))
+        logger.info(f'Collected {len(collected_plugins)} plugins!')
+        logger.info(", ".join([a.__module__ for a in collected_plugins]))
+
+        return collected_plugins
 
     def install_plugin_file(self):
         """Make sure all plugins are installed in the current enviroment."""