Expose a 'decky_plugin' module to decky plugins (#353)

* Expose a 'decky_plugin' module to decky plugins

* expose decky user home path
* support 'py_modules' python modules in plugins
* allow for a '_migration' method in plugins to have an explicit file
  moving step

* Expose the plugin python module as .pyi stub interface

* Expose system and user python paths to plugins

backend/helpers.py

@@ -115,8 +115,18 @@ def mkdir_as_user(path):
 
 # Fetches the version of loader
 def get_loader_version() -> str:
-    with open(os.path.join(os.path.dirname(sys.argv[0]), ".loader.version"), "r", encoding="utf-8") as version_file:
-        return version_file.readline().replace("\n", "")
+    try:
+        with open(os.path.join(os.path.dirname(sys.argv[0]), ".loader.version"), "r", encoding="utf-8") as version_file:
+            return version_file.readline().replace("\n", "")
+    except:
+        return ""
+
+# returns the appropriate system python paths
+def get_system_pythonpaths() -> list[str]:
+    # run as normal normal user to also include user python paths
+    proc = subprocess.run(["python3", "-c", "import sys; print(':'.join(x for x in sys.path if x))"],
+                          user=get_user_id(), env={}, capture_output=True)
+    return proc.stdout.decode().strip().split(":")
 
 # Download Remote Binaries to local Plugin
 async def download_remote_binary_to_path(url, binHash, path) -> bool:

backend/plugin.py

@@ -9,7 +9,7 @@ from logging import getLogger
 from traceback import format_exc
 from os import path, setgid, setuid, environ
 from signal import SIGINT, signal
-from sys import exit
+from sys import exit, path as syspath
 from time import time
 import helpers
 from updater import Updater
@@ -66,6 +66,7 @@ class PluginWrapper:
             environ["USER"] = "root" if "root" in self.flags else helpers.get_user()
             environ["DECKY_VERSION"] = helpers.get_loader_version()
             environ["DECKY_USER"] = helpers.get_user()
+            environ["DECKY_USER_HOME"] = helpers.get_home_path()
             environ["DECKY_HOME"] = helpers.get_homebrew_path()
             environ["DECKY_PLUGIN_SETTINGS_DIR"] = path.join(environ["DECKY_HOME"], "settings", self.plugin_directory)
             helpers.mkdir_as_user(environ["DECKY_PLUGIN_SETTINGS_DIR"])
@@ -77,11 +78,19 @@ class PluginWrapper:
             environ["DECKY_PLUGIN_NAME"] = self.name
             environ["DECKY_PLUGIN_VERSION"] = self.version
             environ["DECKY_PLUGIN_AUTHOR"] = self.author
+            # append the loader's plugin path to the recognized python paths
+            syspath.append(path.realpath(path.join(path.dirname(__file__), "plugin")))
+            # append the plugin's `py_modules` to the recognized python paths
+            syspath.append(path.join(environ["DECKY_PLUGIN_DIR"], "py_modules"))
+            # append the system and user python paths
+            syspath.extend(helpers.get_system_pythonpaths())
             spec = spec_from_file_location("_", self.file)
             module = module_from_spec(spec)
             spec.loader.exec_module(module)
             self.Plugin = module.Plugin
 
+            if hasattr(self.Plugin, "_migration"):
+                get_event_loop().run_until_complete(self.Plugin._migration(self.Plugin))
             if hasattr(self.Plugin, "_main"):
                 get_event_loop().create_task(self.Plugin._main(self.Plugin))
             get_event_loop().create_task(self._setup_socket())