Overriding ansible_local provisioner settings

[MK]

I'm have a box that uses ansible_local provisioning, which is defined in the Vagrant file included with the box:

config.vm.provision :ansible_local do |ansible|
  ansible_root = "/home/vagrant/provision"
  ansible.provisioning_path = ansible_root
  ansible.playbook = "#{ansible_root}/playbook.yml"
end

This works, but now I need to pass a variable to Ansible while provisioning a specific machine, i.e. I need to override the default provisioning settings.

At first I tried this (in the local Vagrantfile, which should override values in the box's Vagrantfile):

config.vm.provision :ansible_local do |ansible|
 ansible.extra_vars = {"develop_mode": true}
end

This is no good, because Vagrant replaces the entire provision block instead of merging, and then complains that there's no playbook path defined. Let's try this:

config.vm.provision :ansible_local do |ansible|
  ansible_root = "/home/vagrant/provision"
  ansible.provisioning_path = ansible_root
  ansible.playbook = "#{ansible_root}/playbook.yml"
  ansible.extra_vars = {"develop_mode": true}
end

Now, Vagrant can run the provisioner, but the `develop_mode` variable doesn't get set correctly. This is the output from Ansible:

TASK: [build | debug ] **************************************************
ok: [default] => {
    "var": {
        "develop_mode": "develop_mode"
    }
}

There are a couple of Vagrant 1.8.1 bugs about this, so here's a suggested workaround (using `raw_arguments` instead of `extra_vars`):

config.vm.provision :ansible_local do |ansible|
  ansible_root = "/home/vagrant/provision"
  ansible.provisioning_path = ansible_root
  ansible.playbook = "#{ansible_root}/playbook.yml"
  ansible.raw_arguments = ["--extra-vars", "develop_mode=true"]
end

Still no good, same Ansible output as before:

TASK: [build | debug ] **************************************************
ok: [default] => {
    "var": {
        "develop_mode": "develop_mode"
    }
}

Maybe I need to use an override in the local Vagrantfile?

config.vm.provider "virtualbox" do |vbox, override|
  override.vm.provision :ansible_local do |ansible|
    ansible_root = "/home/vagrant/provision"
    ansible.provisioning_path = ansible_root
    ansible.playbook = "#{ansible_root}/playbook.yml"
    ansible.raw_arguments = ["--extra-vars", "'develop_mode=true'"]
  end
end

No, still the same Ansible output as before. Is there a way to do what I'm trying to do?

FYI, here's the expected output as generated from running `ansible-playbook` directly on the VM:

TASK: [build | debug ] **************************************************
ok: [localhost] => {
    "var": {
        "develop_mode": "true"
    }
}