Formatted modify

[sampsyo]

There are a number of cool things we could do if the modify command supported templates in the value part. For example, you could put the Echo Nest liveness into the comments field like so:

$ beet mod comments='liveness: $liveness'

It might also be nice to expose these rewritings in an import hook also.

[sampsyo]

It's becoming increasingly clear that people would like to apply format-like changes automatically to tags as well as manually, so this ticket should definitely include that.

As proposed in #1310, it would even be useful to apply transformations globally to all tags. That is, rather than configuring every tag separately to lower-case its value with title=%lower{$title}, artist=%lower{$artist}, etc., a global pattern would apply to every tag. Some people clearly also want to use %asciify{} the same way.

[Bercio]

Another nice use case (especially if implemented as an import hook) would be to default a field to something else in case of an Unknown value, e.g.:beet modify composer::^$ composer = $albumartist

[PierreRust]

Hi,

following my recent mail, I've been thinking about this feature and I'll try to sum up how I see it :

Formatted tag modification would be usable with the import and the modify command

beets import  PATH tagName1='<expr1>' tagName2='<expr2>'
beets mod QUERY tagName1='<expr1>' tagName2='<expr2>'

where <expr> can contains

• references to other tags value : beet mod comments='liveness: $liveness'
• a template function : beet import /path/to/album title='%lower{$title}'

When importing, it would set the tag to the specified templatized value. If a variable is used in the expression, it's value would be the value produced by the import process (i.e. either from the file or form auto-tagging ).

It would also be possible to specify such transformation in the configuration file, with a plugin, to be applied to every import. A simple evolution of the (renamed) zero plugin is probably enough,

zero:
fields: genre 
genre: 
    match : [rnb, 'power metal' , 'Default Genre']
    value : 'Default Genre'

The only thing that does not fit (yet?) in this approach is the global pattern suggested by @sampsyo : it could be implemented with a * tag in the plugin configuration, but I'm not sure how that would fit on the commandline interface, may something like beet import /path/to/album *='%lower{$*}'

Additionnal note on implementation : it could probably be done in Model.setitem (db.py) : this path is used in all the aforementioned use-cases and template evaluation is already available.

[PierreRust]

Ok, I just made a first pull request (only for the modify use case) , but it seems so trivial that I'm wondering if I'm not missing something obvious here...

[PierreRust]

Now I working on the import use case and I'm considering where the tag manipulation should happen (that is, when should we execute tagName1='<expr1>' ). It seems to me it requires a new stage in the pipeline that would be placed just after the plugins stages and before the manipulate_files stage. Of course, as it's the first time I really have a look at the import implementation, it might be completely wrong ...

Any idea / comment on this ?

[l-t-k]

+1, This would be really cool!

[GuilhermeHideki]

About the commandline interface, I think it would be better if we don't have to write %__{$*}. Something like:

beet import /path/to/album  *='lower,asciify' or --apply='lower,asciify'