Re: Downloading from generated mirror

[Jonathan Maw <jonathan maw codethink co uk>]

On 2018-04-30 12:56, Valentin David wrote:
>  2. Multiple directories
>  -----------------------
>
> For some plugins, in #330, there is an extra component in the path. It
> is a number incrementing from 0. There are some plugins that might get
> new incompatible repositories or files for a same URL. And when we
> detect this, we create a new directory.
>
>  - ostree and git should not suffer of this problem, because we can
> just compose repositories and collisions are unlikely.
>  - zip and tar need it when the file is changed.
>  - bzr needs it, when we detect that remote repository does not contain
> at least all the commits we have locally.
>
> The loop that tries mirrors should retry while counting on the last
> path component for those plugins requiring it.
>
> There must be now two exceptions raised from source plugins:
>  - one that says the URL works but the reference is not available,
>  - another one for any other error.
> The loop should count until it find the second error.

Hi Valentin,

Looking at this, the Source.fetch() method currently expects a 
SourceError
to be raised whenever there's a network error or if the source reference
couldn't be matched.

Do you think it would help backwards-compatibility if we keep to 
returning
SourceErrors, but distinguish between the two cases based on the error's
"reason" field?

e.g. in GitSource we extend assert_ref to have the reason "no-ref", and 
use
any other SourceError when fetching as a reason to stop looping and try
another alias mapping.