Removing currently selected spool causes an error to occur

[mdziekon]

Problem description

In a situation where currently selected spool is being removed (as in, deleted from the database), the following error occurs:

SPM:ERROR: Load current selected spools data
An unknown error occurred while loading data

In Octoprint's console:

octoprint_1  | 2023-07-07 00:16:34,194 - octoprint - ERROR - Exception on /plugin/SpoolManager/loadSelectedSpools [GET]
octoprint_1  | Traceback (most recent call last):
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/flask/app.py", line 2529, in wsgi_app
octoprint_1  |     response = self.full_dispatch_request()
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/flask/app.py", line 1825, in full_dispatch_request
octoprint_1  |     rv = self.handle_user_exception(e)
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/flask/app.py", line 1823, in full_dispatch_request
octoprint_1  |     rv = self.dispatch_request()
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/flask/app.py", line 1799, in dispatch_request
octoprint_1  |     return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/octoprint/util/__init__.py", line 1686, in wrapper
octoprint_1  |     return f(*args, **kwargs)
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/octoprint_SpoolManager/api/SpoolManagerAPI.py", line 929, in handleLoadSelectedSpools
octoprint_1  |     for selectedSpool in self.loadSelectedSpools()
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/octoprint/util/__init__.py", line 1686, in wrapper
octoprint_1  |     return f(*args, **kwargs)
octoprint_1  |   File "/octoprint/plugins/lib/python3.8/site-packages/octoprint_SpoolManager/api/SpoolManagerAPI.py", line 143, in loadSelectedSpools
octoprint_1  |     "Last selected Spool for Tool %d from plugin-settings not found in database. Maybe deleted in the meantime." % i)
octoprint_1  | NameError: name 'i' is not defined

---

Proposed resolution

• Before performing the delete, check whether the spool is currently selected, and if so, deselect it
• (Optional) Add confirmation before deleting currently selected spool

Is this a regression caused by fork's changes?

No.

In fact this behavior has improved significantly compares to 1.7.0. On that version, removing selected spool causes the entire Spool's UI to fail without an error message.