Re: Old 0install can't run an alias created by a newer version

On 20 May 2015 at 01:06, Tim Cuthbertson <[email protected]> wrote:
> I'm mostly using the development ocaml version on my own machine. But
> sometimes I end up running a released python (or even ocaml) version.
> Unfortunately, this means I can't run any of my newer aliases, as I get:
>
> Traceback (most recent call last):
>   File "/home/tim/dev/0install/zi-stable/0install", line 14, in <module>
>     main(sys.argv[1:])
>   File "/home/tim/dev/0install/zi-stable/zeroinstall/cmd/__init__.py", line
> 381, in main
>     cmd.handle(config, options, args)
>   File "/home/tim/dev/0install/zi-stable/zeroinstall/cmd/run.py", line 39,
> in handle
>     r = app.get_requirements()
>   File "/home/tim/dev/0install/zi-stable/zeroinstall/apps.py", line 389, in
> get_requirements
>     setattr(r, k, v)
> AttributeError: 'Requirements' object has no attribute 'may_compile'
>
>
> I guess this is my fault for running multiple versions of 0install, but
> that's actually difficult to avoid sometimes. In some cases I end up inside
> a shell (e.g 0env) which is making use of the old python ZeroInstall.xml
> feed, so the python 0install ends up on my path. In other cases, I run the
> released version of 0install (e.g on my mac laptop) but I have a single
> ~/.config/0install/ that I share between machines via a git repo.
>
>
> I'm not sure what should be done about this. Some options:
>
> 1) only save requirement flags which are explicitly specified at creation
> time, and rely on the defaults for other flags
>
> 2) ignore requirement keys which we don't understand, for forwards
> compatibility.
>
> (1) is probably harder, but (2) opens us up to silently ignoring important
> requirements. So I'd vote for (1).

(1) sounds right to me too. Looks like we already do it for some of
the options (e.g. --os):

https://github.com/0install/0install/blob/d9c8219d603176a77d2650322f7054463b1c58c6/ocaml/zeroinstall/requirements.ml#L102


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