list resources will not work correctly

[Roger Peppe]

This bug is in the gopkg.in/charmrepo.v2-unstable package, but affects
juju-core directly.

In Client.listResources in charmstore/client.go there's the following code:

    resmap, err := c.csWrapper.ListResources(ch.Channel, []*charm.URL{ch.URL})
    if err != nil {
       return nil, errors.Trace(err)
    }

    resources, ok := resmap[ch.URL.String()]
    if !ok {
        // no resources for that url, that's ok.
        return nil, nil
    }

The csWrapper.ListResources call invokes the csclient.Client.ListResources
method. This code is if there are some resources, the map returned by that
method will contain a single entry with the key ch.URL.String().

Unfortunately that's not the case, because the Client.ListResources
method removes the revision number from the URL before
making the actual HTTP API call, and the keys in the result map
will never contain the revision numbers.

So if ch.URL contains a revision number (which it will), Client.listResources will never
return any resources, which will mean the juju-core code won't
work correctly.

[Eric Snow (ericsnowcurrently)]

Fixes:

https://github.com/juju/charmrepo/pull/86 (merged)
https://github.com/juju/charmrepo/pull/87 (merged)
http://reviews.vapour.ws/r/4549/ (pending merge))