import and hg 0.9.4

[Horst Gutmann]

Hi :)

With hg 0.9.4 there seems to be a new import override that causes bzr to die a painful death when importing bzr_hg:

 zerok@akira:~/.python/bin$ bzr help
 Unable to load plugin 'hg' from '/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/plugins'
 bzr: ERROR: exceptions.AttributeError: 'module' object has no attribute 'transactions'

 Traceback (most recent call last):
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 729, in run_bzr_catch_errors
     return run_bzr(argv)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 681, in run_bzr
     cmd_obj = get_cmd_object(cmd, plugins_override=not opt_builtin)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 142, in get_cmd_object
     return _get_cmd_object(cmd_name, plugins_override)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 157, in _get_cmd_object
     cmds = _get_cmd_dict(plugins_override=plugins_override)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 123, in _get_cmd_dict
     d = _builtin_commands()
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/commands.py", line 102, in _builtin_commands
     import bzrlib.builtins
   File "/Users/zerok/.python/lib/python2.5/site-packages/mercurial/demandimport.py", line 83, in _demandimport
     return _origimport(name, globals, locals, fromlist)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/builtins.py", line 1216, in <module>
     class cmd_init(Command):
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/builtins.py", line 1247, in cmd_init
     registry=bzrdir.format_registry,
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/lazy_import.py", line 109, in __getattribute__
     return getattr(obj, attr)
   File "/Users/zerok/.python/lib/python2.5/site-packages/mercurial/demandimport.py", line 74, in __getattribute__
     self._load()
   File "/Users/zerok/.python/lib/python2.5/site-packages/mercurial/demandimport.py", line 46, in _load
     mod = _origimport(head, globals, locals)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 1431, in <module>
     class BzrDirFormat4(BzrDirFormat):
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/bzrdir.py", line 1444, in BzrDirFormat4
     _lock_class = lockable_files.TransportLock
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/lazy_import.py", line 109, in __getattribute__
     return getattr(obj, attr)
   File "/Users/zerok/.python/lib/python2.5/site-packages/mercurial/demandimport.py", line 74, in __getattribute__
     self._load()
   File "/Users/zerok/.python/lib/python2.5/site-packages/mercurial/demandimport.py", line 46, in _load
     mod = _origimport(head, globals, locals)
   File "/Users/zerok/.python/lib/python2.5/site-packages/bzrlib/lockable_files.py", line 30, in <module>
     import bzrlib.transactions as transactions
 AttributeError: 'module' object has no attribute 'transactions'

mwhudson pointed me to this bug: http://www.selenic.com/mercurial/bts/issue605

I then tried the following and it seems to work (have only tried pulling so far, though):

=== modified file '__init__.py'
--- __init__.py 2007-07-11 14:56:50 +0000
+++ __init__.py 2007-07-20 14:43:29 +0000
@@ -31,6 +31,9 @@
 import os
 import stat

+import mercurial.demandimport
+mercurial.demandimport.enable = lambda: None
+
 import mercurial.commands
 import mercurial.cmdutil
 import mercurial.hg

[Michael Hudson-Doyle (mwhudson)]

I'm going to assign this to Tim Hatch, because he recently look in bzr-hg's direction, or something...

[Jelmer Vernooij (jelmer)]

  status triaged
  importance high

Renders bzr-hg unusable for people that have hg 0.9.4.

[Tim Hatch (timhatch)]

Yep, we knew this was going to be an issue. I saw other demandimport related issues pop up in the TracMercurial plugin -- and just like in TracMercurial (see Trac rev 5796), we need to make sure that it still works for 0.9.3 users. I'm attaching a patch (applied to my branch at https://code.launchpad.net/~timhatch/bzr-hg/tim already) which should work around the issue for the time being for both 0.9.3 and 0.9.4.

Mercurial really would rather have this stuff enabled [some circular references mentioned in issue605?, in addition to the obvious speed considerations], so I'd like to eventually look for a better fix (after we get 0.9.3 working reliably).

[Robert Collins (lifeless)]

I've merged Tim's import fix to the trunk.