[QML] New Wallet Creation Blocked if the User Needs to Preserve a Wallet File with Forgotten Password

[nc50lc]

Description

With the introduction of this commit: github.com/spesmilo/electrum/commit/378a9e61122ac669ad230fcddf8729af5f0cd27f
It's now required to unlock a wallet file before the user can create a new one.

However, it's limiting certain situations like this: bitcointalk.org/index.php?topic=5584784.0
TL;DR: OP doesn't have a seed phrase backup (needs confirmation) and can't remember his old password.
Deleting the wallet file by clearing Electrum's data isn't an option since he don't have a backup of it.
So, he can't create a new wallet in the latest version.

A feature that's letting the user to backup the wallet files right in the wallet list menu should be enough to fix it.
So that he can save a backup of the encrypted wallet file to the local disk and then clear the app's data to be able to create a new wallet.

[f321x]

With the introduction of this commit ... It's now required to unlock a wallet file before the user can create a new one.

This was done because we simultaneously closed the loophole you describe here with 3b028b0. Otherwise it would be annoying for the user if they go through the wizard to set up a new wallet and then can't remember any existing password.

The unified password is for example necessary to be able to use the biometric authentication.
In the long run it will also allow to simplify the QML codebase (making it more maintainable) if there are only wallets with unified password (but ofc there are still old wallets around so we cannot rely on this atm).

We considered the case that happened to user satashi_nokamato, however our reasoning was basically the same as described by hosemary:

If you have the seed phrase or the old wallet is empty, there's nothing to worry about.
If you have funds in your old wallet and you don't have the seed phrase, you should try to remember your password before deleting your old wallet(s).
If you have funds in your old wallet, you don't have the seed phrase and you can't remember your password, you have already lost your funds.

I agree a wallet file export could help in this situation, satashi_nokamato could export it and try to remember the password later or brute force it. However note this would also allow someone else getting hands on the unlocked phone to export wallet files (easily) and try brute forcing them, especially considering most users probably use a rather weak password on mobile.

As a immediate workaround for satashi_nokamato, maybe he can root his phone without wiping the data and then export the app data?

Related #10345, #9075, #6805

[SomberNight]

A feature that's letting the user to backup the wallet files right in the wallet list menu should be enough to fix it.

We might add a wallet file export feature in the future, I think it might be useful.

but the app would only let the user export the wallet after the user proved they can unlock the wallet. That's the only safe way of doing it, as otherwise typical wallet passwords used on Android are too weak to protect against offline bruteforce.
So that would not help here.