POC for an extensible bulk command

[nfraprado]

This is a proof-of-concept for a new bulk command that is basically a generic version of bulkrename that can be extended by the user, that is, it provides an interface for the user to add custom functions that query and edit any attribute of multiple files at once.

ISSUE TYPE

• Improvement/feature implementation

CHECKLIST

• The CONTRIBUTING document has been read [REQUIRED]
• All changes follow the code style [REQUIRED]
• All new and existing tests pass [REQUIRED]
• Changes require config files to be updated
  • Config files have been updated
• Changes require documentation to be updated
  • Documentation has been updated
• Changes require tests to be updated
  • Tests have been updated

DESCRIPTION

The bulkrename command provides a convenient way to edit an attribute of multiple files at once, but it is also very limited since it can only be used for renaming the files.

The new bulk command requires that the user adds two functions: one that gets the attribute for the file, and another that generates the shell script command that makes the change of the file attribute to the new one set by the user.

So the user can extend this command by providing the functions that handle the specific attribute they want to change, and the bulk command handles the common stuff that was already done by bulkrename: open the editor with the attribute for each file in each line, get the changes made by the user on exit, create a shell script with the commands for each attribute changed and finally execute the script for the changes to take effect.

MOTIVATION AND CONTEXT

This brings more flexibility and use cases for the useful but limited bulkrename.

TESTING

As an example of usage, two functions were implemented that use the bulk command, id3art and id3tit. They use the eyeD3 program to edit the artist and title ID3 tags of mp3 files, respectively.

To illustrate the usage, the users can for example: in ranger, select multiple mp3 files that they want to change the artist ID3 tag, type :bulk id3art, the editor will open up with the artist of each music file in each line.
After editing and closing, a shell script opens up with the eyeD3 commands that change the artist tag of each one that was modified.
Finally, after reviewing this script and closing, the changes take place.

IMAGES / VIDEOS

[toonn]

Looks promising. I'm secretly hoping we can replace bulkrename with this, aliasing it.

[toonn]

Hmm, would be nice if this worked more like image preview methods, where you can register a method. That way this code wouldn't have to be copied and edited but people could you define a class and register.

[nfraprado]

Indeed it is better. I too found using this dictionary cumbersome, but didn't know which better interface to use.

I now have added a new ext/bulk.py file containing the same interface used in the image preview methods but for these bulk commands. I was going to add it all inside the bulk(Command) class but decorator definition doesn't seem to work inside classes, or I'm doing something wrong. But it looked a little too chaotic anyway, so I moved everything to the new file (except for the commands).

I also made the id3_artist and id3_title bulk commands extend a base BulkCommand class. That way users can use the base class as reference for which functions need to be implemented and which are the parameters.
This got me thinking though, if the user should already extend this base class, we could require only BulkCommand to be extended and not the decorator to also be used to register a bulk command. This would remove the ability to have the class named differently from its nickname (which can be passed to the decorator), but this is already the case for ranger's commands.

[nfraprado]

Thank you for reviewing, @toonn .

Some thoughts and my TODO list for this:

• When I based this code in bulkrename, I removed the last bit where it retags the files, since it is only useful when files are being renamed, and not for every other attribute changes. If we're expecting this to replace bulkrename and be totally compatible, we should add it be back and have a property in each BulkCommand saying that it moves/renames files, so the retagging can occur for those cases.
• We still need to add tab completion for this command but should be pretty easy using the already available tab function.
• Until now I have referred to the bulk(Command) as the "bulk command" and to id3_artist and id3_title as "bulk commands", but this is very confusing both in the code and when writing about. Instead of "bulk commands" I thought of these alternatives: "bulk attributes" or "bulk subcommands". Suggestions?

[toonn]

Hmm, you're right about the retagging. Maybe a general "post command hook?" That way you can define the actions that need to be taken after the command completes. Which could be a "Blah blah finished!" message by default but be overridden with retagging for example.

I think bulk subcommands is going to be the most straightforward terminology, Attributes works well in many cases but might not in all cases, like paths aren't really attributes of files.

[nfraprado]

Hmm, you're right about the retagging. Maybe a general "post command hook?" That way you can define the actions that need to be taken after the command completes. Which could be a "Blah blah finished!" message by default but be overridden with retagging for example.

Yes, that sounds even better. I'll add that as a third function in the BulkCommand class then, and also implement bulkrename using it to make sure it works ok.

I think bulk subcommands is going to be the most straightforward terminology, Attributes works well in many cases but might not in all cases, like paths aren't really attributes of files.

Sounds good. I'll rename the code to use that terminology.