Make password generator length use existing length if available

[kneitinger]

Description

Adds optional length parameter to PasswordGeneratorWidget::reset() (default=0), which when >0 sets the length SpinBox's value to the value passed in. The EditEntryWidget already called reset() when the password at a time when was known, so the current length was just added to this call (accounts for empty passwords correctly)

This seems like a clean approach to me, as the use of the default parameter keeps all previous usage the same, except when a value is passed in. Another approach could be to add a public PasswordGeneratorWidget::setLength() function. If that is more desired, I would be happy to do that instead.

Edit: Additionally, I made the change discussed in my comment below. Now, if the entry edit is closed without saving, any changes to the password generator length will not carry over into new entries.

Motivation and context

Fixes #2180
Fixes undesirable behavior discussed in comments of #2318

How has this been tested?

1. Changed the value of [generator]->Length to something recognizable

   $ grep ^Length ~/.config/keepassxc/keepassxc.ini
   Length=53
   

2. Opened keepassxc and began creating a new entry. Expanded generator section, and verified that the length still honors that value:
   
3. Opened various entries, all having different lengths and verified that they inherit their existing length:
   
   
4. Created new entry and expanded generator section. It is the last used length (in this case 8). This is identical to the current behavior, happy to change it if another behavior is desired: The length is still the value of [generator]->Length
   
   I then cancelled this entry (this is important for the next step).
5. Opened standalone password generator, and it is still using the value of [generator]->Length at startup. The generator widget always retains its last state in memory, since it is always just hidden and shown. It does not actually commit its length to the ini until a generated password is actually used, therefore the standalone generator will not inherit the last used value of a cancelled generation.
   
6. Created a new test entry with a 44 character generated password and saved it. Checked the ini file, and the length is changed to 44. Opened standalone generator, and length is set to 44:
   

Types of changes

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

Checklist:

• ✅ I have read the CONTRIBUTING document. [REQUIRED]
• ✅ My code follows the code style of this project. [REQUIRED]
• ✅ All new and existing tests passed. [REQUIRED]
• ✅ I have compiled and verified my code with -DWITH_ASAN=ON. [REQUIRED]

[kneitinger]

Thinking about it more, I don't really feel that the password generator widget keeping its last used length value as the in-memory equivalent of [generator]->Length is the best behavior when the password is not applied. For example if I open a new entry, expand the pw gen section, set length to 2, and cancel the close the entry without saving; the next time I open a new entry, the length will still be 2 instead of the most recent applied length.

Instead I feel like it should it should:

• Reset its value to the saved [generator]->Length upon closing the entry without using the generated password.
• Retain its value if the entry the generated password is used and the entry is saved. This is the criteria in which [generator]->Length is committed to the ini file, and in my opinion makes more sense.

This would mean that the standalone generator, the generator widget (on a new or passwordless entry), and the ini file are always consistent with each other.

This behavior would be different from how keepassxc currently behaves (regardless of looking at password existing password length), however, I think it makes more sense than having the length that wasn't even used carry over into fresh entries.

[kneitinger]

Edited PR description to reflect most recent commit.

[droidmonkey]

Good point, agree

[TheZ3ro]

Nice contribution!