Tag command breaks badly with empty repository

[Gustavo Niemeyer]

[niemeyer@burma ~]% mkdir a
[niemeyer@burma ~]% cd a
[niemeyer@burma ~/a]% bzr init --format=dirstate-tags
[niemeyer@burma ~/a]% bzr tag foo
bzr: ERROR: exceptions.KeyError: <type 'NoneType'>

Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 650, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 612, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 304, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.4/site-packages/bzrlib/builtins.py", line 3470, in run
    branch.tags.set_tag(tag_name, revision_id)
  File "/usr/lib/python2.4/site-packages/bzrlib/tag.py", line 87, in set_tag
    self._set_tag_dict(td)
  File "/usr/lib/python2.4/site-packages/bzrlib/tag.py", line 137, in _set_tag_dict
    self._serialize_tag_dict(new_dict))
  File "/usr/lib/python2.4/site-packages/bzrlib/tag.py", line 144, in _serialize_tag_dict
    return bencode.bencode(td)
  File "/usr/lib/python2.4/site-packages/bzrlib/util/bencode.py", line 299, in bencode
    encode_func[type(x)](x, r)
  File "/usr/lib/python2.4/site-packages/bzrlib/util/bencode.py", line 279, in encode_dict
    encode_func[type(v)](v, r)
KeyError: <type 'NoneType'>

bzr 0.15.0candidate2 on python 2.4.4.candidate.1 (linux2)
arguments: ['/usr/bin/bzr', 'tag', 'foo']

** please send this report to <email address hidden>

[John A Meinel (jameinel)]

This seems to be 2-fold

First, with no commits "bzr tag foo" is creating a tag and pointing it at None, which I don't think we really want.

This is being exposed at the bencode layer, because bencode cannot handle None.

bencode should probably be exposing a better exception, but since it isn't our code, we may just need to do that at a higher level.

But I *think* the 'bzr tag' command should just complain "You are trying to create a tag pointing to None".

Either that, or it should change tags pointing to None into pointing them at "null:". But I probably would rather not expose "null:" if we can help it.

[Martin Pool (mbp)]

I agree with John

[Tim Hatch (timhatch)]

I also agree with John, having just hit this. Something along the lines of:

=== modified file 'bzrlib/builtins.py'
--- bzrlib/builtins.py 2007-07-23 19:37:15 +0000
+++ bzrlib/builtins.py 2007-07-27 22:24:01 +0000
@@ -3847,6 +3847,10 @@
                     revision_id = revision[0].in_history(branch).rev_id
                 else:
                     revision_id = branch.last_revision()
+ if not revision_id:
+ raise errors.BzrCommandError(
+ "Tags can not be placed on an empty branch, "
+ "try making a commit first")
                 if (not force) and branch.tags.has_tag(tag_name):
                     raise errors.TagAlreadyExists(tag_name)
                 branch.tags.set_tag(tag_name, revision_id)

[Martin Pool (mbp)]

That looks like a reasonable placeholder.

--
Martin

[Martin Pool (mbp)]

Has now been fixed; a tag pointing to the empty revision is created.

[Martin Pool (mbp)]

However, I still have a patch around originally from Tim Hatch that seems to fix this in a different way, by declining to tag the origin. That may be a better ui.