detecting version match/mismatch between core/plugins

[Aaron Bentley]

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Wichmann, Mats D wrote:
>>>It would be easy enough to have a version number in the plugin and
>>>fail to load it if it's too low or high, it would just 
>>>require someone to write the code :) 
>>
>>I think its up to the plugin to do that... keeps them more like regular
>>python files.
> 
> 
> Haven't followed up to last few comments, but I
> think I agree that it's the plugin that needs to
> have most of the "smarts".

Here's what I'm considering adding to bzrtools:

import bzrlib


__version__ = '0.9'


def check_bzrlib_version(desired_str):
    """Check that bzrlib is compatible.

    If version is < bzrtools version, assume incompatible.
    If version == bzrtools version, assume completely compatible
    If version == bzrtools version + 1, assume compatible, with deprecations
    Otherwise, assume incompatible.
    """
    desired = tuple([int(num) for num in desired_str.split('.')])
    desired_plus = (desired[0], desired[1]+1)
    bzrlib_version = [int(num) for num in bzrlib.__version__.split('.')[:2]]
    bzrlib_version = tuple(bzrlib_version)
    if bzrlib_version == desired:
        return
    try:
        from bzrlib.trace import warning
    except ImportError:
        # get the message out any way we can
        from warnings import warn as warning
    if bzrlib_version < desired:
        warning('Installed bzr version %s is too old to be used with
bzrtools'
                ' %s.' % (bzrlib.__version__, __version__))
        # Not using BzrNewError, because it may not exist.
        raise Exception, 'Version mismatch'
    else:
        warning('Bzrtools is not up to date with installed bzr version'
                ' %s. Please upgrade to bzrtools %i.%i.'
                % (bzrlib.__version__, bzrlib_version[0],
bzrlib_version[1]))
        if bzrlib_version != desired_plus:
            raise Exception, 'Version mismatch'


check_bzrlib_version(__version__)
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