[MERGE] Mail clients listed in a registry

[John Arbash Meinel]

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Neil Martinsen-Burrell wrote:
> Here is a patch to make mail clients extensible by plugins by listing
> them in a registry. While Bazaar may reasonably try to support all
> popular mail clients, there will always be niche programs and platforms
> that we can't support.  There will also be times where some vaporware
> exists to support a certain client, but it hasn't landed yet.  (This is
> currently the case with Mail.app.)
> 
> The patch makes it possible to add a mail client from a plugin as the
> attached plugin demonstrates.  (This email sent using Mail.app and that
> plugin.)  Test coverage is still adequate as we currently test the
> getting of mail_clients from Config objects for every built-in client.
> 
> -Neil
> 

Hmm.. weird.
It seems your __init__.py script was shown inline, but your bzr patch was not.
 I started reviewing it, thinking it was the patch. It might have been a
little better to do 2 separate emails. (__init__.py doesn't really conform to
some of our coding standards, but it doesn't really matter as it is *your*
plugin.)


+from bzrlib.mail_client import mail_client_registry
 """)

^- I really prefer it if lazy_import is only done on module objects. So
instead do:

from bzrlib import mail_client

...
  mail_client.mail_client_registry.get(selected_client)

(If there is already a "from bzrlib import" then mail_client should be
inserted into that list.)

+mail_client_registry.register_lazy(
+                'editor',
+                'bzrlib.mail_client',
+                'Editor')

^- There is no reason to use "register_lazy" as you have declared the class
*right there*. 'register_lazy' is for when the declared class may not need to
be imported at all.

For example, if you defined the mail_client_registry in config.py and then
used 'register_lazy' on everything.

In this particular case, I'm happier seeing 'mail_client_registry' in
mail_client.py and having the mail_client.py module not get loaded until you
need it.

So these should generally become:

mail_client_registry.register('editor', Editor)

Eventually it might be nice to add help strings, as then we can auto-generate
documentation for them. But that is certainly outside the scope of your change.

BB:tweak

John
=:->


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