Given the following code:

    >>> import dnf
    >>> base = dnf.Base()
    >>> base.conf.substitutions['releasever'] = '26'
    >>> repo = dnf.repo.Repo('fedora', parent_conf=base.conf)
    >>> repo.metalink = 'https://mirrors.fedoraproject.org/metalink?repo=fedora-$releasever&arch=$basearch'
    >>> base.repos.add(repo)
    >>> repo.skip_if_unavailable = False
    >>> repo.enable()
    >>> repo.load()

It fails with:

    Traceback (most recent call last):
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 229, in _perform
        return super(_Handle, self).perform(result)
      File "/usr/lib64/python3.6/site-packages/librepo/__init__.py", line 1517, in perform
        _librepo.Handle.perform(self, result)
    librepo.LibrepoException: (15, 'Cannot prepare internal mirrorlist: file "repomd.xml" was not found in metalink', 'Bad mirrorlist or metalink file')
    
    During handling of the above exception, another exception occurred:
    
    Traceback (most recent call last):
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 910, in load
        self._handle_load(handle)
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 657, in _handle_load
        return self._handle_load_core(handle)
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 670, in _handle_load_core
        result = handle._perform()
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 233, in _perform
        raise _DetailedLibrepoError(exc, source)
    dnf.repo._DetailedLibrepoError
    
    During handling of the above exception, another exception occurred:
    
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib/python3.6/site-packages/dnf/repo.py", line 922, in load
        raise dnf.exceptions.RepoError(msg)
    dnf.exceptions.RepoError: Failed to synchronize cache for repo 'fedora'


I've realized the problem is in the matalink that is not substituted:

    >>> repo.metalink
    'https://mirrors.fedoraproject.org/metalink?repo=fedora-$releasever&arch=$basearch'

    >>> repo.metalink = dnf.conf.parser.substitute(repo.metalink, base.conf.substitutions)
    >>> repo.metalink
    'https://mirrors.fedoraproject.org/metalink?repo=fedora-26&arch=x86_64'

Reading the documentation didn't give me any idea I have to do this manually.

I believe this might be fixed with one of the following:

  1) Make metalink (and possibly baseurl as well) a property and do the substitution on setting it.

  2) Make .load() do the substitution.

  3) Document the current behavior in [1] - say "When setting the matalink, no substitution will happen, you need to manually call dnf.conf.parser.substitute() if you want the substitution of variables like $releasever to happen."

[1] http://dnf.readthedocs.io/en/latest/api_repos.html#dnf.repo.Repo.metalink

Version-Release number of selected component (if applicable):
dnf-2.5.0-2.fc26.noarch