PICARD-1044: Allow the usage of scripting for loading local cover art

[zas]

Summary

• This is a…
  • Bug fix
  • Feature addition
  • Refactoring
  • Minor / simple change (like a typo)
  • Other
• Describe this change in 1-2 sentences:

Problem

The dialog for saving cover art supports the use of scripting, but the dialog for loading local cover art does not (it only supports regex). It would be very helpful if you could use the scripting there as well, so you could search for a more specific filename, such as "Cover\Album Artist - Album [Date].ext".

• JIRA ticket (optional): PICARD-1044

Solution

• add a checkbox to select the mode (regex or script)
• add a script editor widget, along error/example
• provide evalutation time methods accordingly

AI Usage

In accordance with the AI use policy portion of the MetaBrainz Contribution Guidelines, the level of AI/LLM use in the development of this Pull Request is:

• No AI/LLM use
• Minimal use (e.g. autocompletion)
• Moderate use (e.g. suggestions regarding code fragments)
• Significant use (e.g. code structure, tests development, etc.)
• Primarily AI developed
• Other (please specify below)

Action

Additional actions required:

• Update Picard documentation (please include a reference to this PR)
• Other (please specify below)

[phw]

Generally code looks fine and this seems to work.
I just wonder how useful this is, as it only works with exact matches. I initially thought we might be able to allow scripting but still have regex matching.

But this will become difficult, as it would be extremely tricky to have the script return a valid regex. We could escape all variables beforehand, but this then makes the variables difficult to use.

But could we have the resulting filename allow glob matching? So users could have * or ? returned as part of the filename for partial matches. It could be an option.

Also we could allow matching the file name case insensitive.

[zas]

Not sure what is the exact use case for this, maybe ask to the 2 people asking for it in the ticket.
At least they can test this code to see if it fits their needs.
Not sure it should be merged (hence the draft)

[rdswift]

A bit of thinking out loud here, but rather than using script_to_filename(), perhaps you could use ScriptParser.eval() to generate the regular expression to be used for checking the file names. That way the user could include reserved characters in the expression by escaping them (simlar to how it's done in the $rsearch() and $rreplace() scripting functions.

EDIT: There could even be a text box or label showing the regular expression created so the user could check that it made sense for them?

EDIT 2: For example, if the user entered something like:

.*%album%\\.\(png|jpg\)\$

would yield the regular expression:

.*Abbey Road\.(png|jpg)$

EDIT 3: Might need a new scripting function like $rsanitize() to replace invalid filename characters with regular expression wildcards to give you something like (assuming the album is "Back in Black" by AC/DC):

.*$rsanitize(%albumartist% - %album%)\\.\(png|jpg\)\$

would yield the regular expression:

.*AC.DC - Back in Black\.(png|jpg)$

[rdswift]

Just thinking that this might even allow the users to set track-specific cover art. Not something that I would want to do, but I've seen some users ask about this.

[rdswift]

EDIT 3: Might need a new scripting function like $rsanitize() to replace invalid filename characters with regular expression wildcards

Actually, that could already be accomplished using the $rreplace() scripting function.