Reintroduce the disk compaction process as a unique step

builder/hyperv/common/step_compact_disk.go

@@ -0,0 +1,50 @@
+package common
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/packer/helper/multistep"
+	"github.com/hashicorp/packer/packer"
+)
+
+type StepCompactDisk struct {
+	SkipCompaction bool
+}
+
+// Run runs a compaction/optimisation process on attached VHD/VHDX disks
+func (s *StepCompactDisk) Run(_ context.Context, state multistep.StateBag) multistep.StepAction {
+	driver := state.Get("driver").(Driver)
+	ui := state.Get("ui").(packer.Ui)
+
+	if s.SkipCompaction {
+		ui.Say("Skipping disk compaction...")
+		return multistep.ActionContinue
+	}
+
+	// Get the tmp dir used to store the VMs files during the build process
+	var tmpPath string
+	if v, ok := state.GetOk("packerTempDir"); ok {
+		tmpPath = v.(string)
+	}
+
+	ui.Say("Compacting disks...")
+	// CompactDisks searches for all VHD/VHDX files under the supplied
+	// path and runs the compacting process on each of them. If no disks
+	// are found under the supplied path this is treated as a 'soft' error
+	// and a warning message is printed. All other errors halt the build.
+	result, err := driver.CompactDisks(tmpPath)
+	if err != nil {
+		err := fmt.Errorf("Error compacting disks: %s", err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+	// Report disk compaction results/warn if no disks were found
+	ui.Message(result)
+
+	return multistep.ActionContinue
+}
+
+// Cleanup does nothing
+func (s *StepCompactDisk) Cleanup(state multistep.StateBag) {}

builder/hyperv/iso/builder.go

@@ -466,6 +466,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		&hypervcommon.StepUnmountFloppyDrive{
 			Generation: b.config.Generation,
 		},
+		&hypervcommon.StepCompactDisk{
+			SkipCompaction: b.config.SkipCompaction,
+		},
 		&hypervcommon.StepExportVm{
 			OutputDir:  b.config.OutputDir,
 			SkipExport: b.config.SkipExport,

builder/hyperv/vmcx/builder.go

@@ -475,6 +475,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		&hypervcommon.StepUnmountFloppyDrive{
 			Generation: b.config.Generation,
 		},
+		&hypervcommon.StepCompactDisk{
+			SkipCompaction: b.config.SkipCompaction,
+		},
 		&hypervcommon.StepExportVm{
 			OutputDir:  b.config.OutputDir,
 			SkipExport: b.config.SkipExport,