Pause between boot_commands when debugging a Virtualbox build

When debugging a build (or maintaining an existing packer file), teach `packer build -debug` how to step through individual `boot_command`s in order to triage the packer file.

builder/virtualbox/common/step_type_boot_command.go

@@ -38,11 +38,17 @@ type StepTypeBootCommand struct {
 }
 
 func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction {
+	debug := state.Get("debug").(bool)
 	driver := state.Get("driver").(Driver)
 	httpPort := state.Get("http_port").(uint)
 	ui := state.Get("ui").(packer.Ui)
 	vmName := state.Get("vmName").(string)
 
+	var pauseFn multistep.DebugPauseFn
+	if debug {
+		pauseFn = state.Get("pauseFn").(multistep.DebugPauseFn)
+	}
+
 	s.Ctx.Data = &bootCommandTemplateData{
 		"10.0.2.2",
 		httpPort,
@@ -50,7 +56,7 @@ func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction
 	}
 
 	ui.Say("Typing the boot command...")
-	for _, command := range s.BootCommand {
+	for i, command := range s.BootCommand {
 		command, err := interpolate.Render(command, &s.Ctx)
 		if err != nil {
 			err := fmt.Errorf("Error preparing boot command: %s", err)
@@ -81,6 +87,10 @@ func (s *StepTypeBootCommand) Run(state multistep.StateBag) multistep.StepAction
 				return multistep.ActionHalt
 			}
 
+			if pauseFn != nil {
+				pauseFn(multistep.DebugLocationAfterRun, fmt.Sprintf("boot_command[%d]: %s", i, command), state)
+			}
+
 			if err := driver.VBoxManage("controlvm", vmName, "keyboardputscancode", code); err != nil {
 				err := fmt.Errorf("Error sending boot command: %s", err)
 				state.Put("error", err)

builder/virtualbox/iso/builder.go

@@ -268,15 +268,18 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 	state := new(multistep.BasicStateBag)
 	state.Put("cache", cache)
 	state.Put("config", &b.config)
+	state.Put("debug", b.config.PackerDebug)
 	state.Put("driver", driver)
 	state.Put("hook", hook)
 	state.Put("ui", ui)
 
 	// Run
 	if b.config.PackerDebug {
+		pauseFn := common.MultistepDebugFn(ui)
+		state.Put("pauseFn", pauseFn)
 		b.runner = &multistep.DebugRunner{
 			Steps:   steps,
-			PauseFn: common.MultistepDebugFn(ui),
+			PauseFn: pauseFn,
 		}
 	} else {
 		b.runner = &multistep.BasicRunner{Steps: steps}

builder/virtualbox/ovf/builder.go

@@ -42,6 +42,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 	// Set up the state.
 	state := new(multistep.BasicStateBag)
 	state.Put("config", b.config)
+	state.Put("debug", b.config.PackerDebug)
 	state.Put("driver", driver)
 	state.Put("cache", cache)
 	state.Put("hook", hook)
@@ -134,9 +135,11 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 
 	// Run the steps.
 	if b.config.PackerDebug {
+		pauseFn := common.MultistepDebugFn(ui)
+		state.Put("pauseFn", pauseFn)
 		b.runner = &multistep.DebugRunner{
 			Steps:   steps,
-			PauseFn: common.MultistepDebugFn(ui),
+			PauseFn: pauseFn,
 		}
 	} else {
 		b.runner = &multistep.BasicRunner{Steps: steps}