Expose default vagrantfile template as a template variable {{.DefaultTemplate}}

[dangra]

The whole point is to pass a vagrantfile template that can extend the default template.
As a consequence, this PR also includes tests for template source field not tested until now.

source "vagrant" "foo" {
  communicator         = "ssh"
  source_path          = "some/box"
  provider             = "virtualbox"
  template             = "Vagrantfile.tpl"
}

# Vagrantfile.tpl
{{ .DefaultTemplate }}

Vagrant.configure("2") do |config|
  config.vm.provider "virtualbox" do |vb|
    vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']
  end
end

[hashicorp-cla]

All committers have signed the CLA.

[dangra]

I still find this useful and it comes with tests to validate it works as expected :)

[nywilken]

Hi @dangra apologies for the longer then normal review process. We haven't had the chance to prioritize this review. We have however selected the PR and will provide feedback if you are still interested in working on the change. Thanks!

[dangra]

I still rely on a workaround so will be happy to discuss further improvements to get this merged

[nywilken]

Thanks again @dangra the changes look good to me so far. From looking at the code and description you are essentially making the template variable {{.DefaultTemplate}} available for users. Which gives the option of generating a template file containing multiple version configuration blocks like the following:

Vagrant.configure("2") do |config|
  # Generated by the vagrant builder.... contents of {{.DefaultTemplate}}
end

Vagrant.configure("2") do |config|
  # some other pre-exisiting configuration 
end

Would you mind sharing details on your use case so I can better understand the why.

That said, If you could add a comment to the builder file here for the {{.DefaultTemplate}}. Maybe something like example below and run make generate that would update all the documentation files.

+       // Alternatively, the template variable `{{.DefaultTemplate}}` is available for
+       // use if you wish extend the default generated template.

I'm also happy to update the docs for you on this PR but I would like to understand the use case better to add a little more light as to why in the docs.

[dangra]

@nywilken that is exactly it.

My use case is the same I posted in the example at the top, I need to enable Nested Harward Virtualization when packing with Virtualbox provider, so this line:

vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']

I current workaround (without this patch) is to define a template that duplicates the default template plus above line:

# Vagrantfile.template
Vagrant.configure("2") do |config|
  config.vm.define "source", autostart: false do |source|
    source.vm.box = "{{.SourceBox}}"
    config.ssh.insert_key = {{.InsertKey}}
  end
  config.vm.define "output" do |output|
    output.vm.box = "{{.BoxName}}"
    output.vm.box_url = "file://package.box"
    config.ssh.insert_key = {{.InsertKey}}
  end
  {{ if ne .SyncedFolder "" -}}
  config.vm.synced_folder "{{.SyncedFolder}}", "/vagrant"
  {{- else -}}
  config.vm.synced_folder ".", "/vagrant", disabled: true
  {{- end}}

  config.vm.provider "virtualbox" do |vb|
    vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']
  end
end

but this is not ideal, I'd prefer to always use the default plus my customization for whatever is the default on that packer version.

So, ideally:

{{ .DefaultTemplate }}

Vagrant.configure("2") do |config|
  config.vm.provider "virtualbox" do |vb|
    vb.customize ['modifyvm', :id, '--nested-hw-virt', 'on']
  end
end

I hope that makes more sense. thanks!

[dangra]

That said, If you could add a comment to the builder file here for the {{.DefaultTemplate}}. Maybe something like example below and run make generate that would update all the documentation files.

+       // Alternatively, the template variable `{{.DefaultTemplate}}` is available for
+       // use if you wish extend the default generated template.

Done

[nywilken]

Great thanks for the update. I rebased and pushed up the changes. I will merge and release once all goes green.