[PATCH] python plugins in BZRPATH using Command structure

[John A Meinel]

Aaron Bentley wrote:
> mbp at sourcefrog.net wrote:
> | Why not just list them directly on your path?
> 
> You might as well ask 'why not list the plugin filenames directly'?
> 
> I like plugin systems that support the 'dump it in a directory and
> you're done' approach.  I think that's convenient and understandable.
> This system supports that, but only for files.
> 
> It would also be nice to support updating your plugins with bzr.  But
> bzr only does updates in terms of working trees, not files.  So if we
> want to allow people to
> 
> 1. install plugins with minimum fuss
> 2. update plugins using bzr
> 
> then I think the obvious way is to allow working trees to be placed in
> plugin directories.
> 
> Aaron

I've been thinking about it, what if we support "__init__.py" for
directories.

So you have BZRPLUGINPATH which can contain .py files, but can also
contain directories. If the directory has an __init__.py file, the
directory will be imported just like all the other files. It means that
the person working on the bzr tree needs to add
from newcommand import *
to __init__.py whenever they add a new command to their project.

This is one possibility.

One small fix that I probably need to add is to handle having files with
the same name. By default 'import' caches the module in sys.modules so
that re-importing something with the same name gives the same module.
Since I am messing with sys.path so that I can dynamically import from a
new directory, if there are 2 files with the same name they potentially
conflict.

Actually, I think __init__.py fixes this problem, since in that
circumstance it makes the import get a prefix (so if in test/__init__.py
you import bzrlib it shows up in sys.modules as test.bzrlib).

If you wanted to be cruel, you could make BZRPLUGINPATH use __init__.py,
but then the person needs to manually update it, rather than just drop
in a file.

My current favorite is to just use what we I wrote. bzr searches all of
BZRPLUGINPATH, and recurses 1 directory to look for .py files, which it
then imports and looks for cmd_* functions. If it finds any, it adds
them to the command list.

I'm flexible, but since we have ExternalCommands added, I would really
like to see python native plugins also exist somehow in bzr proper.

John
=:->
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