Cleanup after unloading extension. (#3226)

* Cleanup after unloading extension, resolve #3223.

* Remove leftover modules loaded from `plugins` path when purging.

---------

Co-authored-by: Taku <[email protected]>

Author: Jerrie-Aries

CHANGELOG.md

@@ -12,6 +12,7 @@ however, insignificant breaking changes do not guarantee a major version bump, s
 - `?alias make/create` as aliases to `?alias add`. This improves continuity between the bot and its command structure. ([PR #3195](https://github.com/kyb3r/modmail/pull/3195))
 - Loading the blocked list with the `?blocked` command takes a long time when the list is large. ([PR #3242](https://github.com/kyb3r/modmail/pull/3242))
 - Reply not being forwarded from DM. (PR [#3239](https://github.com/modmail-dev/modmail/pull/3239))
+- Cleanup imports after removing/unloading a plugin. ([PR #3226](https://github.com/modmail-dev/Modmail/pull/3226))
 
 ### Added
 - `?log key <key>` to retrieve the log link and view a preview using a log key. ([PR #3196](https://github.com/modmail-dev/Modmail/pull/3196))

cogs/plugins.py

@@ -264,6 +264,17 @@ async def load_plugin(self, plugin):
             logger.error("Plugin load failure: %s", plugin.ext_string, exc_info=True)
             raise InvalidPluginError("Cannot load extension, plugin invalid.") from exc
 
+    async def unload_plugin(self, plugin: Plugin) -> None:
+        try:
+            await self.bot.unload_extension(plugin.ext_string)
+        except commands.ExtensionError as exc:
+            raise exc
+
+        ext_parent = ".".join(plugin.ext_string.split(".")[:-1])
+        for module in list(sys.modules.keys()):
+            if module == ext_parent or module.startswith(ext_parent + "."):
+                del sys.modules[module]
+
     async def parse_user_input(self, ctx, plugin_name, check_version=False):
 
         if not self.bot.config["enable_plugins"]:
@@ -378,7 +389,7 @@ async def plugins_add(self, ctx, *, plugin_name: str):
             logger.warning("Unable to download plugin %s.", plugin, exc_info=True)
 
             embed = discord.Embed(
-                description=f"Failed to download plugin, check logs for error.\n{type(e)}: {e}",
+                description=f"Failed to download plugin, check logs for error.\n{type(e).__name__}: {e}",
                 color=self.bot.error_color,
             )
 
@@ -397,7 +408,7 @@ async def plugins_add(self, ctx, *, plugin_name: str):
                 logger.warning("Unable to load plugin %s.", plugin, exc_info=True)
 
                 embed = discord.Embed(
-                    description=f"Failed to download plugin, check logs for error.\n{type(e)}: {e}",
+                    description=f"Failed to load plugin, check logs for error.\n{type(e).__name__}: {e}",
                     color=self.bot.error_color,
                 )
 
@@ -438,7 +449,7 @@ async def plugins_remove(self, ctx, *, plugin_name: str):
 
         if self.bot.config.get("enable_plugins"):
             try:
-                await self.bot.unload_extension(plugin.ext_string)
+                await self.unload_plugin(plugin)
                 self.loaded_plugins.remove(plugin)
             except (commands.ExtensionNotLoaded, KeyError):
                 logger.warning("Plugin was never loaded.")
@@ -480,9 +491,10 @@ async def update_plugin(self, ctx, plugin_name):
             await self.download_plugin(plugin, force=True)
             if self.bot.config.get("enable_plugins"):
                 try:
-                    await self.bot.unload_extension(plugin.ext_string)
+                    await self.unload_plugin(plugin)
                 except commands.ExtensionError:
                     logger.warning("Plugin unload fail.", exc_info=True)
+
                 try:
                     await self.load_plugin(plugin)
                 except Exception:
@@ -529,17 +541,20 @@ async def plugins_reset(self, ctx):
         for ext in list(self.bot.extensions):
             if not ext.startswith("plugins."):
                 continue
+            logger.error("Unloading plugin: %s.", ext)
             try:
-                logger.error("Unloading plugin: %s.", ext)
-                await self.bot.unload_extension(ext)
-            except Exception:
-                logger.error("Failed to unload plugin: %s.", ext)
-            else:
-                if not self.loaded_plugins:
-                    continue
                 plugin = next((p for p in self.loaded_plugins if p.ext_string == ext), None)
                 if plugin:
+                    await self.unload_plugin(plugin)
                     self.loaded_plugins.remove(plugin)
+                else:
+                    await self.bot.unload_extension(ext)
+            except Exception:
+                logger.error("Failed to unload plugin: %s.", ext)
+
+        for module in list(sys.modules.keys()):
+            if module.startswith("plugins."):
+                del sys.modules[module]
 
         self.bot.config["plugins"].clear()
         await self.bot.config.update()