Show a clear error if the key is found but the slots are not configured

[w15eacre]

• Fix the error message when a key is connected, but no slots are configured
• The solution is to check connected devices. If they exist, show the error: "Hardware keys found, but no slots are configured."
• Fix missing SCardDisconnect
• Fix outdated test cases

Fixes issue #11543

Screenshots

Testing strategy

• Check the fix on YubiKeys
• Add a unit test to verify the series numbers of connected devices

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[droidmonkey]

Our minimum version of Qt is 5.12 now so you should be able to use qScopeGuard template function instead of redefining a ScopeGuard. https://doc.qt.io/qt-5/qscopeguard.html#qScopeGuardx

This message should also appear on the database open widget. We can show the same disabled drop down box as the database security view and also disable the checkbox too.

[w15eacre]

I tried the first time but Ubuntu build failed on CI

[droidmonkey]

Note the case, qScopeGuard not QScopeGuard

[w15eacre]

@droidmonkey Thanks for your review; I have fixed it.
In my opinion, If I added a new item in the combobox I would refactor the noHardwareKeysFoundLabel and move it into this combobox. This behavior would be the same as in the Database Security view.

[droidmonkey]

I don't like that the keys are basically polled twice just to get an error message. Instead, I tweaked the findValidKeys function to include a reference parameter that populates the number of keys actually found. This is then stored in the Yubikey class for use in the new connectedKeys function. This actually unwinds a lot of the new code you provided, but is way more elegant.

What do you think?

[w15eacre]

Yes, it's better and safer. Besides, polling twice caused an issue with the calling function that could freeze the UI thread. I suggest replacing:

• int& → unsigned int8_t& or size_t&. This value is in the range [0, 4).
• int Delay → std::chrono::milliseconds for a clearer understanding of this interval.

@droidmonkey What do you think about it?

[droidmonkey]

int& → unsigned int8_t& or size_t&. This value is in the range [0, 4).

The sign of the counter variable is irrelevant in this context and can actually produce underflow errors if you were to code in a -- by accident (ie, instead of -1 you'll get UINT_MAX). Either way this won't happen or matter because that isn't how this variable is handled in any context of the code. Generally speaking, the "only" time you need to use unsigned int is to use the full 32-bit length of an int to represent the numbers you need.

int Delay → std::chrono::milliseconds for a clearer understanding of this interval.

You cannot do this because std::chrono::milliseconds is actually a class and not convertible to an int to be used with Qt. It is not meant to indicate the variable contents by a name.

[droidmonkey]

Also, I tested this code with my 5 yubikeys and NFC reader, it worked flawlessly and reliably. Merging now.