Cleanup VM in case of a failure (#120)

* Cleanup VM in case of a failure

* Extracted cleanup in a separate step

* Improved message

builder/tart/builder.go

@@ -77,7 +77,9 @@ func (b *Builder) Prepare(raws ...interface{}) (generatedVars []string, warnings
 }
 
 func (b *Builder) Run(ctx context.Context, ui packer.Ui, hook packer.Hook) (packer.Artifact, error) {
-	steps := []multistep.Step{}
+	steps := []multistep.Step{
+		new(stepCleanVM), // cleanup the VM if the build is cancelled or halted
+	}
 
 	if b.config.HTTPDir != "" || len(b.config.HTTPContent) != 0 {
 		if errs := b.config.HTTPConfig.Prepare(interpolate.NewContext()); len(errs) != 0 {

builder/tart/step_cleanup.go

@@ -0,0 +1,26 @@
+package tart
+
+import (
+	"context"
+	"github.com/hashicorp/packer-plugin-sdk/multistep"
+	packersdk "github.com/hashicorp/packer-plugin-sdk/packer"
+)
+
+type stepCleanVM struct{}
+
+func (s *stepCleanVM) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {
+	return multistep.ActionContinue
+}
+
+func (s *stepCleanVM) Cleanup(state multistep.StateBag) {
+	config := state.Get("config").(*Config)
+	ui := state.Get("ui").(packersdk.Ui)
+
+	_, cancelled := state.GetOk(multistep.StateCancelled)
+	_, halted := state.GetOk(multistep.StateHalted)
+	if cancelled || halted {
+		ui.Say("Cleaning up virtual machine...")
+		cmdArgs := []string{"delete", config.VMName}
+		_, _ = TartExec(context.Background(), cmdArgs...)
+	}
+}