Hi all,
The recent virtualenv breakage in Python 2.6.8 and 2.7.3 reveals an
issue that deserves to be explicitly addressed in PEP 405: what happens
when the system Python underlying a venv gets an in-place bugfix
upgrade. If the bugfix includes a simultaneous change to the interpreter
and standard library such that the older interpreter will not work with
the newer standard library, all venvs created from that Python
installation will be broken until the new interpreter is copied into them.
Choices for how to address this:
1) Document it and provide a tool for easily upgrading a venv in this
situation. This may be adequate. In practice the situation is quite
rare: 2.6.8/2.7.3 is the only actual example in the history of
virtualenv that I'm aware of. The disadvantage is that if the problem
does occur, the error will probably be quite confusing and seemingly
unrelated to pyvenv.
2) In addition to the above, introduce a versioning marker in the
standard library (is there one already?) and have some code somewhere
(insert hand-waving here) check sys.version_info against the stdlib
version, and fail fast with an unambiguous error if there is a mismatch.
This makes the failure more explicit, but at the significant cost of
making it more common: at every mismatch, not just in the
apparently-rare case of a breaking change.
3) Symlink the interpreter rather than copying. I include this here for
the sake of completeness, but it's already been rejected due to
significant problems on older Windows' and OS X.
4) Adopt a policy of interpreter/stdlib cross-compatibility within a
given X.Y version of Python. I don't expect this to be a popular choice,
given the additional testing requirements it imposes, but it would
certainly be the nicest option from the PEP 405 standpoint (and may also
be complementary to proposals for splitting out the stdlib). In the
2.6.8/2.7.3 case, this would have been technically trivial to do, but
the choice was made not to do it in order to force virtualenv users to
adopt the security-fixed Python interpreter.
Thoughts?
Carl
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
