Molecule generates wrong Vagrantfile when not defining 'provider'

[lukas-beumer]

As we have different environments, where we need to run molecule tests. We have a curious problem.

We have defined the driver in molecule.yml:

driver:
  name: vagrant

Running our tests, molecule will choose the correct provider automatically. In our case virtualbox or libvirt. In default virtualbox is the default provider, but if it's not installed, libvirt will be chosen (if it's installed). The virtual machines will be setup, but not with the correct settings, if defined (like memory or cpus).

The problem is, that the underlying Vagrantfile will be generated for "virtualbox", even if it's not installed and the virtual machines were setup up for libvirt. Only if I define "libvirt" as provider in the molecule.yml, the file will be generated correctly. So the drive don't use the same driver as vagrant, if not set explicity

[apatard]

The problem is that it's vagrant itself which is choosing the "right" driver, and at time of writing the Vagrantfile, we have no way to know if vagrant will use a different driver. Vagrant will choose say libvirt instead of vbox when reading the Vagrantfile, which is too late, since here, it means when launching the VM.
The same problem may happen without molecule-vagrant. Just create a Vagrantfile for vmware driver and you'll likely see vagrant using vbox or libvirt.

There has been ansible-community/molecule-vagrant#174 about similar problem. I've suggested to have a rewrite to create an option to allow forcing the provider but nothing happened yet. Maybe I'll create a PR.

The other possibility would be to write the Vagrantfile, maybe use vagrant provider to check the provider which will be used and exit with an error if it's not the one configured ("fun point": this command possibly works at VM level not Vagrantfile). Also python-vagrant doesn't support the vagrant provider command, so it needs to be updated first. Possible, but complicated.

fwiw, the vagrant plugin command can't be used to detect that the provider is the correct one.