Merge lp:~jderose/desktopcouch/ctx-should-default-to-None into lp:desktopcouch

[Jason Gerard DeRose]

Make context function-argument default-value None so that callers need not concern themselves with complex imports.

Small change to make it easier for 3rd-party apps to use destopcouch test idioms (this is a problem for dmedia).

[Eric Casteleijn (thisfred)]

I think I'm missing the point of this change. In what scenario would this make a difference? Is it to do with the import time instantiation of default arguments?

[Jason Gerard DeRose (jderose)]

It's so that internal details (that ctx defaults to desktopcouch.local_files.DEFAULT_CONTEXT) don't leak into subclasses, other functions/classes using it. It's also best-practice in the Python standard library... optional/keyword args default to simple, predictable values, most often None, sometime True/False, etc.

For example, in dmedia I need to provide a custom context when testing (Chad help me with this so I can test the same way desktopcouch itself does), but I don't want to deal with the desktopcouch.local_files.DEFAULT_CONTEXT detail myself.

See the dmedia MetaStore.__init__() on line 109: http://bazaar.launchpad.net/~jderose/dmedia/trunk/annotate/head%3A/dmedialib/metastore.py?start_revid=104

[Eric Casteleijn (thisfred)]

Fair enough, and I agree with keeping default kw arguments as simple as possible, since they can definitely bite you on the ass if you don't :)

review: Approve

[Vincenzo Di Somma (vds)]

review: Approve

=== modified file 'desktopcouch/records/server.py'
--- desktopcouch/records/server.py	2010-11-04 11:01:31 +0000
+++ desktopcouch/records/server.py	2010-11-08 10:41:55 +0000
@@ -60,7 +60,9 @@
  
     def __init__(self, database, uri=None, record_factory=None, create=False,
                  server_class=OAuthCapableServer, oauth_tokens=None,
-                 ctx=desktopcouch.local_files.DEFAULT_CONTEXT):
+                 ctx=None):
+        if ctx is None:
+            ctx = desktopcouch.local_files.DEFAULT_CONTEXT
         self.ctx = ctx
         self.server_uri = uri
         super(CouchDatabase, self).__init__(