Ensure updating loader tag supported (#1494)

The loader tag is required when nvram is being enabled. Ensure it is
marked as a requirement of validation and also support it's
configuration during the start domain action.

lib/vagrant-libvirt/action/start_domain.rb

@@ -375,12 +375,32 @@ module VagrantPlugins
                 end
               end
 
+              loader = REXML::XPath.first(xml_descr, '/domain/os/loader')
+              if config.loader
+                if loader.nil?
+                  descr_changed = true
+                  loader = REXML::Element.new('loader')
+                  REXML::XPath.first(xml_descr, '/domain/os').insert_after('//type', loader)
+                  loader.text = config.loader
+                else
+                  if (loader.text or '').strip != config.loader
+                    descr_changed = true
+                    loader.text = config.loader
+                  end
+                end
+                loader.attributes['type'] = config.nvram ? 'pflash' : 'rom'
+              elsif !loader.nil?
+                descr_changed = true
+                loader.parent.delete_element(loader)
+              end
+
               undefine_flags = 0
               nvram = REXML::XPath.first(xml_descr, '/domain/os/nvram')
               if config.nvram
                 if nvram.nil?
                   descr_changed = true
-                  nvram = REXML::Element.new('nvram', REXML::XPath.first(xml_descr, '/domain/os'))
+                  nvram = REXML::Element.new('nvram')
+                  REXML::XPath.first(xml_descr, '/domain/os').insert_after(loader, nvram)
                   nvram.text = config.nvram
                 else
                   if (nvram.text or '').strip != config.nvram

lib/vagrant-libvirt/config.rb

@@ -994,6 +994,10 @@ module VagrantPlugins
           errors << "libvirt.qemu_use_agent must be a boolean."
         end
 
+        if !@nvram.nil? && @loader.nil?
+          errors << "use of 'nvram' requires a 'loader' to be specified, please add one to the configuration"
+        end
+
         if @qemu_use_agent == true
           # if qemu agent is used to optain domain ip configuration, at least
           # one qemu channel has to be configured. As there are various options,

spec/unit/action/start_domain_spec.rb

@@ -66,6 +66,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
       context 'when being added to existing' do
         let(:vagrantfile_providerconfig) do
           <<-EOF
+          libvirt.loader = "/path/to/loader/file"
           libvirt.nvram = "/path/to/nvram/file"
           EOF
         end
@@ -85,6 +86,7 @@ describe VagrantPlugins::ProviderLibvirt::Action::StartDomain do
       context 'when it was already in use' do
         let(:vagrantfile_providerconfig) do
           <<-EOF
+          libvirt.loader = "/path/to/loader/file"
           libvirt.nvram = "/path/to/nvram/file"
           # change another setting to trigger the undefine/create
           libvirt.cpus = 4

spec/unit/action/start_domain_spec/existing_added_nvram.xml

@@ -6,9 +6,9 @@
   <currentMemory unit='KiB'>2097152</currentMemory>
   <vcpu placement='static'>2</vcpu>
   <os>
-    <type arch='x86_64' machine='pc-i440fx-6.0'>hvm</type>
+    <type arch='x86_64' machine='pc-i440fx-6.0'>hvm</type><loader type='pflash'>/path/to/loader/file</loader><nvram>/path/to/nvram/file</nvram>
     <boot dev='hd'/>
-  <nvram>/path/to/nvram/file</nvram></os>
+  </os>
   <features>
     <acpi/>
     <apic/>

spec/unit/action/start_domain_spec/nvram_domain.xml

@@ -7,8 +7,9 @@
   <vcpu placement='static'>2</vcpu>
   <os>
     <type arch='x86_64' machine='pc-i440fx-6.0'>hvm</type>
-    <boot dev='hd'/>
+    <loader type='pflash'>/path/to/loader/file</loader>
     <nvram>/path/to/nvram/file</nvram>
+    <boot dev='hd'/>
   </os>
   <features>
     <acpi/>

spec/unit/action/start_domain_spec/nvram_domain_other_setting.xml

@@ -7,8 +7,9 @@
   <vcpu placement='static'>4</vcpu>
   <os>
     <type arch='x86_64' machine='pc-i440fx-6.0'>hvm</type>
-    <boot dev='hd'/>
+    <loader type='pflash'>/path/to/loader/file</loader>
     <nvram>/path/to/nvram/file</nvram>
+    <boot dev='hd'/>
   </os>
   <features>
     <acpi/>

spec/unit/action/start_domain_spec/nvram_domain_removed.xml

@@ -7,8 +7,9 @@
   <vcpu placement='static'>2</vcpu>
   <os>
     <type arch='x86_64' machine='pc-i440fx-6.0'>hvm</type>
-    <boot dev='hd'/>
     
+    
+    <boot dev='hd'/>
   </os>
   <features>
     <acpi/>

spec/unit/config_spec.rb

@@ -630,6 +630,24 @@ describe VagrantPlugins::ProviderLibvirt::Config do
       end
     end
 
+    context 'with nvram defined' do
+      before do
+        subject.nvram = '/path/to/some/nvram'
+      end
+
+      it 'should be invalid as loader not set' do
+        assert_invalid
+      end
+
+      context 'with loader defined' do
+        it 'should be valid' do
+          subject.loader = '/path/to/some/loader'
+
+          assert_valid
+        end
+      end
+    end
+
     context 'with cpu_mode and cpu_model defined' do
       it 'should discard model if mode is passthrough' do
         subject.cpu_mode = 'host-passthrough'