provisoners/ansible(both): Accept 'all:vars'

The patterns "all" is a special keyword that target all hosts in the
inventory. Therefore it makes sense to accept "all:vars" as a group
variable name. Note that "*:vars" pattern is not valid in an Ansible
inventory.
See http://docs.ansible.com/ansible/latest/intro_patterns.html#patterns

Fix #7730

CHANGELOG.md

@@ -12,6 +12,7 @@ IMPROVEMENTS:
 BUG FIXES:
 
 - guests/shell_expand_guest_path : Properly expand guest paths that include relative path alias [GH-8918]
+- provisioners/ansible(both): Add the "all:vars" section to the inventory when defined in `groups` option [GH-7730]
 - util/ssh: Properly quote key path for IdentityFile option to allow for spaces [GH-8924]
 
 ## 1.9.8 (August 23, 2017)

plugins/provisioners/ansible/provisioner/base.rb

@@ -228,7 +228,7 @@ module VagrantPlugins
           end
 
           group_vars.each_pair do |gname, gmembers|
-            if defined_groups.include?(gname.sub(/:vars$/, ""))
+            if defined_groups.include?(gname.sub(/:vars$/, "")) || gname == "all:vars"
               inventory_groups += "\n[#{gname}]\n" + gmembers.join("\n") + "\n"
             end
           end

test/unit/plugins/provisioners/ansible/provisioner_test.rb

@@ -396,6 +396,19 @@ VF
           expect(inventory_content).to include("[group3:vars]\nstringvar1=stringvalue1\nstringvar2=stringvalue2\n")
         }.and_return(default_execute_result)
       end
+
+      it "adds 'all:vars' section to the generated inventory" do
+        config.groups = {
+          "all:vars" => { "var1" => "value1", "var2" => "value2" }
+        }
+
+        expect(Vagrant::Util::Subprocess).to receive(:execute).with('ansible-playbook', any_args) { |*args|
+          inventory_content = File.read(generated_inventory_file)
+
+          expect(inventory_content).to include("[all:vars]\nvar1=value1\nvar2=value2\n")
+
+        }.and_return(default_execute_result)
+      end
     end
 
     describe "with host_key_checking option enabled" do