Ensure the export directory structure matches that of previous versions

Commit 3fc2defb6 altered the directory structure associated with an
exported VM. The changes mean that the export process now stores the
exported machine files and folders under a folder with name 'vm_name' in
the output directory.
This commit restores the previous behaviour whereby the exported machine
files and folders were stored directly in the output directory. This
allows us to keep the efficiency improvements introduced with 3fc2defb6
while maintaining backward compatibility.

By default the Export-VM command creates three folders in the specified
export directory - 'Virtual Hard Disks', 'Virtual Machines' and
'Snapshots'. When a machine with no associated snapshots is exported the
'Snapshots' directory is empty.
Prior to 3fc2defb6 the Snapshots folder was not copied/incorporated into
the output directory at all. This was a bug.
This commit preserves the legacy behaviour by not including an empty
Snapshots directory in the export. However, if there *are* Snapshots
associated with the VM, they are now moved into the output directory
along with the usual directories containing disks and VM metadata. This
prevents warnings/errors on import due to missing snapshots.

builder/hyperv/common/driver.go

@@ -94,6 +94,8 @@ type Driver interface {
 
 	ExportVirtualMachine(string, string) error
 
+	PreserveLegacyExportBehaviour(string, string) error
+
 	CompactDisks(string) error
 
 	RestartVirtualMachine(string) error

builder/hyperv/common/driver_mock.go

@@ -186,6 +186,11 @@ type DriverMock struct {
 	ExportVirtualMachine_Path   string
 	ExportVirtualMachine_Err    error
 
+	PreserveLegacyExportBehaviour_Called  bool
+	PreserveLegacyExportBehaviour_SrcPath string
+	PreserveLegacyExportBehaviour_DstPath string
+	PreserveLegacyExportBehaviour_Err     error
+
 	CompactDisks_Called bool
 	CompactDisks_Path   string
 	CompactDisks_Err    error
@@ -481,6 +486,13 @@ func (d *DriverMock) ExportVirtualMachine(vmName string, path string) error {
 	return d.ExportVirtualMachine_Err
 }
 
+func (d *DriverMock) PreserveLegacyExportBehaviour(srcPath string, dstPath string) error {
+	d.PreserveLegacyExportBehaviour_Called = true
+	d.PreserveLegacyExportBehaviour_SrcPath = srcPath
+	d.PreserveLegacyExportBehaviour_DstPath = dstPath
+	return d.PreserveLegacyExportBehaviour_Err
+}
+
 func (d *DriverMock) CompactDisks(path string) error {
 	d.CompactDisks_Called = true
 	d.CompactDisks_Path = path

builder/hyperv/common/driver_ps_4.go

@@ -219,6 +219,10 @@ func (d *HypervPS4Driver) ExportVirtualMachine(vmName string, path string) error
 	return hyperv.ExportVirtualMachine(vmName, path)
 }
 
+func (d *HypervPS4Driver) PreserveLegacyExportBehaviour(srcPath string, dstPath string) error {
+	return hyperv.PreserveLegacyExportBehaviour(srcPath, dstPath)
+}
+
 func (d *HypervPS4Driver) CompactDisks(path string) error {
 	return hyperv.CompactDisks(path)
 }

builder/hyperv/common/step_export_vm.go

@@ -3,6 +3,7 @@ package common
 import (
 	"context"
 	"fmt"
+	"path/filepath"
 
 	"github.com/hashicorp/packer/helper/multistep"
 	"github.com/hashicorp/packer/packer"
@@ -59,6 +60,21 @@ func (s *StepExportVm) Run(_ context.Context, state multistep.StateBag) multiste
 		return multistep.ActionHalt
 	}
 
+	// Shuffle around the exported folders to maintain backwards
+	// compatibility. This moves the 'Snapshots', 'Virtual Hard Disks' and
+	// 'Virtual Machines' directories from <output directory>/<vm name> so
+	// they appear directly under <output directory>. The empty '<output
+	// directory>/<vm name>' directory is removed when complete.
+	// The 'Snapshots' folder will not be moved into the output directory
+	// if it is empty.
+	exportPath := filepath.Join(s.OutputDir, vmName)
+	err = driver.PreserveLegacyExportBehaviour(exportPath, s.OutputDir)
+	if err != nil {
+		// No need to halt here; Just warn the user instead
+		err = fmt.Errorf("WARNING: Error restoring legacy export dir structure: %s", err)
+		ui.Error(err.Error())
+	}
+
 	return multistep.ActionContinue
 }
 

common/powershell/hyperv/hyperv.go

@@ -665,6 +665,62 @@ if (Test-Path -Path ([IO.Path]::Combine($path, $vmName, 'Virtual Machines', '*.V
 	return err
 }
 
+func PreserveLegacyExportBehaviour(srcPath, dstPath string) error {
+
+	var script = `
+param([string]$srcPath, [string]$dstPath)
+
+# Validate the paths returning an error if they are empty or don't exist
+$srcPath, $dstPath | % {
+    if ($_) {
+        if (! (Test-Path $_)) {
+            [System.Console]::Error.WriteLine("Path $_ does not exist")
+            exit
+        }
+    } else {
+        [System.Console]::Error.WriteLine("A supplied path is empty")
+        exit
+    }
+}
+
+# Export-VM should just create directories at the root of the export path
+# but, just in case, move all files as well...
+Move-Item -Path (Join-Path (Get-Item $srcPath).FullName "*.*") -Destination (Get-Item $dstPath).FullName
+
+# Move directories with content; Delete empty directories
+$dirObj = Get-ChildItem $srcPath -Directory | % {
+    New-Object PSObject -Property @{
+        FullName=$_.FullName;
+        HasContent=$(if ($_.GetFileSystemInfos().Count -gt 0) {$true} else {$false})
+    }
+}
+foreach ($directory in $dirObj) {
+    if ($directory.HasContent) {
+        Move-Item -Path $directory.FullName -Destination (Get-Item $dstPath).FullName
+    } else {
+        Remove-Item -Path $directory.FullName
+    }
+}
+
+# Only remove the source directory if it is now empty
+if ( $((Get-Item $srcPath).GetFileSystemInfos().Count) -eq 0 ) {
+    Remove-Item -Path $srcPath
+} else {
+    # 'Return' an error message to PowerShellCmd as the directory should
+    # always be empty at the end of the script. The check is here to stop
+    # the Remove-Item command from doing any damage if some unforeseen
+    # error has occured
+    [System.Console]::Error.WriteLine("Refusing to remove $srcPath as it is not empty")
+    exit
+}
+`
+
+	var ps powershell.PowerShellCmd
+	err := ps.Run(script, srcPath, dstPath)
+
+	return err
+}
+
 func CompactDisks(path string) error {
 	var script = `
 param([string]$srcPath)