Multi-series charm authors: new functionality for comparing ubuntu versions

[Alex Kavanagh]

On Thu, Apr 13, 2017 at 10:13 PM, Colin Watson <cjwatson at ubuntu.com> wrote:

> On Thu, Apr 13, 2017 at 09:15:08PM +0100, Alex Kavanagh wrote:
> > So instead of:
> >
> >     if ubuntu_version > 'trusty':
> >
> > We do:
> >
> >     cmp_version = CompareHostReleases(ubuntu_version)
> >     if cmp_version > 'trusty':
> >
> > This version of the code checks that ubuntu_version and 'trusty' strings
> > are known releases and makes it easy to fix existing code.  >, <, >=< <=,
> > ==, != are all supported.
>
> I have déjà vu: I did exactly the same thing in lp:ubuntu-cdimage in
> 2012. :-)  I agree that this style makes things pretty nice for calling
> code.
>
> The one problem I've had with it is that every so often somebody looks
> at a bit of code and says "hey, isn't this going to break after 17.04?"
> and then I have to explain that it's actually magically OK, which as
> problems go is not really a bad one to have.
>

Good to know that I'm not totally going out on a limb with this approach!
There was some criticism of leaving is as >, <, etc., the alternatives just
seemed really clunky.  There is the downside that people could miss it, but
there wasn't a reasonable way of stopping people just using a regular
string comparison.  Thanks for the feedback / confirmation!


>
> --
> Colin Watson                                       [cjwatson at ubuntu.com]
>
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-- 
Alex Kavanagh - Software Engineer
Cloud Dev Ops - Solutions & Product Engineering - Canonical Ltd
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