Support vagrant-vbguest plugin

[tmatilai]

Ensure the proxies are configured before vagrant-vbguest plugin. The plugin hooks to the VagrantPlugins::ProviderVirtualBox::Action::Boot action so it will get executed earlier than us now.

We need to hook to VagrantVbguest::Middleware if it is found. But as that action is only called on VM boot with VirtualBox provider, and the Provision action is still also called, we have to hook to both and add some flag for not configuring the machine twice.

Related issue: dotless-de/vagrant-vbguest#77

[tmatilai]

Another challenge (besides of avoiding multiple executions) is that when hooking to VagrantVbguest::Middleware the configuration has to be done before passing the control to the next middleware action. With Provision actions the logic is kind of backwards...

[tmatilai]

Ugh, yet another issue. It seems that it is not possible to hook after/before an action that has not been added to the middleware stack yet. And vagrant-vbguest plugin is loaded after proxyconf. Won't help to hook to VagrantPlugins::ProviderVirtualBox::Action::Boot either as VagrantVbguest::Middleware would still be injected in-between.

[tmatilai]

This seems to be a blocker for me. I can't think of a way to hook proxyconf actions between VagrantPlugins::ProviderVirtualBox::Action::Boot and VagrantVbguest::Middleware, as the latter will be inserted to the middleware stack only after us.

Any help? @mitchellh, @fgrehm?

[fgrehm]

@tmatilai you should be able to "force" vbguest to be loaded prior to doing your proxyconf magic. an example can be found at multiprovider-snap. Hope that helps :)

[tmatilai]

@fgrehm Thanks! I thought about something like that but didn't try it out as it felt a bit "wrong" as we don't actually depend on the vbguest plugin. But maybe that's the only way. I'll play more with it tonight.

[fgrehm]

I think that's fine, it's sort of like a "loose dependency" ;)

[tmatilai]

I guess you're right. If the plugin is installed (i.e. VagrantVbguest defined), there shouldn't be problem to force the plugin loading. Thanks again!

[tmatilai]

Ok, this seems to be working. Testing and reviewing appreciated. =)

I'll at least add some tests for the Action::OnlyOnce class, but not tonight.

[fgrehm]

I won't be able to test it today but looking at the code things seems to be fine :)
Oh, and good job on the Action::OnlyOnce too ;)

[tmatilai]

Thanks, Fábio!

The trap with OnlyOnce is that the block must always be the same (Proc) instance as that is used as a key. But I couldn't think of any other way without forcing the caller to specify the key explicitly. Still I'm quite happy with it. :)

[tmatilai]

I'll merge this and push a pre-release version to rubygems to make it easier for people to test. Seems to work fine on my manual testing. (I'll keep dreaming of the acceptance tests... :))

[tmatilai]

Released as v0.6.0.rc1, which can be installed by:

vagrant plugin install --plugin-source https://rubygems.org/ --plugin-prerelease vagrant-proxyconf