Incorrect unload order for submodules

[ostr00000]

I believe that this code:

plugin_reloader/reloader_plugin.py

Lines 262 to 267 in 36ddcb2

	# Unload submodules
	for key in [key for key in sys.modules.keys()]:
	if '{}.'.format(plugin) in key:
	if hasattr(sys.modules[key], 'qCleanupResources'):
	sys.modules[key].qCleanupResources()
	del sys.modules[key]

should be executed after call to unloadPlugin method (but before loadPlugin):

plugin_reloader/reloader_plugin.py

Lines 273 to 276 in 36ddcb2

	startTime = time()
	unloadPlugin(plugin)
	loadPlugin(plugin)
	pluginStarted = startPlugin(plugin)

This is because one could make local import in unload function to access for example a global object. If the submodule with the global object is unloaded first, then a new global object is created.
Current behavior is inconsistent with manual reload (menuBar->Plugins->Manage and Install Plugins...->uncheck a plugin and then check it again) - I have no error when reloading plugin from QGIS.

---

Note: Why should one perform local import in initGui and unload methods in QGIS plugin instead of global import?
Because submodules should only be loaded if the plugin is active.
It is especially severe, when a submodule have long load time (ex. fetching data from DB) and despite plugin been disabled, it still impacts QGIS startup time.

[borysiasty]

Hi,

I apologize for the late reply (and the wrong order of commands). Thanks a lot for your investigation, I'll fix it within upcoming weeks!

[borysiasty]

Since QGIS 3.8.4, the unloading submodules is implemented in qgis.utils.unloadPlugin:

https://github.com/qgis/QGIS/pull/9851/files

so I'm just removing it from here. Will be released soon.

[borysiasty]

@ostr00000 Update: Finally I leave that code after unloadPlugin as you proposed, as it turns out that unloadPlugin sometimes leaves leftovers.