Adds `force_delete_snapshot` flag

This PR adds the ability for Packer to clean up snapshots in addition to
deregistering AMIs at build time.

To test this, I used the following `test.json` file:

```json
{
  "builders": [
    {
      "type": "amazon-ebs",
      "region": "us-east-1",
      "source_ami": "ami-fce3c696",
      "ami_name": "packer-test",
      "instance_type": "m3.medium",
      "ssh_username": "ubuntu",
      "vpc_id": "some-vpc-id",
      "subnet_id": "some-subnet-routed-through-igw",
      "security_group_id": "some-security-group-with-port-22-access",
      "force_delete_snapshot": true
    }
  ],
  "provisioners": [
    {
      "type": "shell-local",
      "command": "echo 'hello'"
    }
  ]
}

```

I appreciate any constructive feedbakc that can be given. Cheers!

builder/amazon/chroot/builder.go

@@ -244,8 +244,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		&StepEarlyCleanup{},
 		&StepSnapshot{},
 		&awscommon.StepDeregisterAMI{
-			ForceDeregister: b.config.AMIForceDeregister,
+			ForceDeregister:     b.config.AMIForceDeregister,
-			AMIName:         b.config.AMIName,
+			ForceDeleteSnapshot: b.config.AMIForceDeleteSnapshot,
+			AMIName:             b.config.AMIName,
 		},
 		&StepRegisterAMI{
 			RootVolumeSize: b.config.RootVolumeSize,

builder/amazon/common/ami_config.go

@@ -19,6 +19,7 @@ type AMIConfig struct {
 	AMITags                 map[string]string `mapstructure:"tags"`
 	AMIEnhancedNetworking   bool              `mapstructure:"enhanced_networking"`
 	AMIForceDeregister      bool              `mapstructure:"force_deregister"`
+	AMIForceDeleteSnapshot  bool              `mapstructure:"force_delete_snapshot"`
 	AMIEncryptBootVolume    bool              `mapstructure:"encrypt_boot"`
 	SnapshotTags            map[string]string `mapstructure:"snapshot_tags"`
 }

builder/amazon/common/step_deregister_ami.go

@@ -10,15 +10,16 @@ import (
 )
 
 type StepDeregisterAMI struct {
-	ForceDeregister bool
+	ForceDeregister     bool
-	AMIName         string
+	ForceDeleteSnapshot bool
+	AMIName             string
 }
 
 func (s *StepDeregisterAMI) Run(state multistep.StateBag) multistep.StepAction {
 	ec2conn := state.Get("ec2").(*ec2.EC2)
 	ui := state.Get("ui").(packer.Ui)
 
-	// check for force deregister
+	// Check for force deregister
 	if s.ForceDeregister {
 		resp, err := ec2conn.DescribeImages(&ec2.DescribeImagesInput{
 			Filters: []*ec2.Filter{{
@@ -33,7 +34,7 @@ func (s *StepDeregisterAMI) Run(state multistep.StateBag) multistep.StepAction {
 			return multistep.ActionHalt
 		}
 
-		// deregister image(s) by that name
+		// Deregister image(s) by name
 		for _, i := range resp.Images {
 			_, err := ec2conn.DeregisterImage(&ec2.DeregisterImageInput{
 				ImageId: i.ImageId,
@@ -46,6 +47,25 @@ func (s *StepDeregisterAMI) Run(state multistep.StateBag) multistep.StepAction {
 				return multistep.ActionHalt
 			}
 			ui.Say(fmt.Sprintf("Deregistered AMI %s, id: %s", s.AMIName, *i.ImageId))
+
+			// Delete snapshot(s) by image
+			if s.ForceDeleteSnapshot {
+				for _, b := range i.BlockDeviceMappings {
+					if b.Ebs != nil {
+						_, err := ec2conn.DeleteSnapshot(&ec2.DeleteSnapshotInput{
+							SnapshotId: b.Ebs.SnapshotId,
+						})
+
+						if err != nil {
+							err := fmt.Errorf("Error deleting existing snapshot: %s", err)
+							state.Put("error", err)
+							ui.Error(err.Error())
+							return multistep.ActionHalt
+						}
+						ui.Say(fmt.Sprintf("Deleted snapshot: %s", *b.Ebs.SnapshotId))
+					}
+				}
+			}
 		}
 	}
 

builder/amazon/ebs/builder.go

@@ -165,8 +165,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			EnableEnhancedNetworking: b.config.AMIEnhancedNetworking,
 		},
 		&awscommon.StepDeregisterAMI{
-			ForceDeregister: b.config.AMIForceDeregister,
+			ForceDeregister:     b.config.AMIForceDeregister,
-			AMIName:         b.config.AMIName,
+			ForceDeleteSnapshot: b.config.AMIForceDeleteSnapshot,
+			AMIName:             b.config.AMIName,
 		},
 		&stepCreateAMI{},
 		&stepCreateEncryptedAMICopy{},

builder/amazon/ebs/builder_acc_test.go

@@ -46,6 +46,22 @@ func TestBuilderAcc_forceDeregister(t *testing.T) {
 	})
 }
 
+func TestBuilderAcc_forceDeleteSnapshot(t *testing.T) {
+	// Build the same AMI name twice, with force_delete_snapshot on the second run
+	builderT.Test(t, builderT.TestCase{
+		PreCheck:             func() { testAccPreCheck(t) },
+		Builder:              &Builder{},
+		Template:             buildForceDeleteSnapshotConfig("false", "dereg"),
+		SkipArtifactTeardown: true,
+	})
+
+	builderT.Test(t, builderT.TestCase{
+		PreCheck: func() { testAccPreCheck(t) },
+		Builder:  &Builder{},
+		Template: buildForceDeleteSnapshotConfig("true", "dereg"),
+	})
+}
+
 func TestBuilderAcc_amiSharing(t *testing.T) {
 	builderT.Test(t, builderT.TestCase{
 		PreCheck: func() { testAccPreCheck(t) },
@@ -254,6 +270,21 @@ const testBuilderAccForceDeregister = `
 }
 `
 
+const testBuilderAccForceDeleteSnapshot = `
+{
+	"builders": [{
+		"type": "test",
+		"region": "us-east-1",
+		"instance_type": "m3.medium",
+		"source_ami": "ami-76b2a71e",
+		"ssh_username": "ubuntu",
+		"force_deregister": "%s",
+		"force_delete_snapshot": "%s",
+		"ami_name": "packer-test-%s"
+	}]
+}
+`
+
 // share with catsby
 const testBuilderAccSharing = `
 {
@@ -284,6 +315,10 @@ const testBuilderAccEncrypted = `
 }
 `
 
-func buildForceDeregisterConfig(name, flag string) string {
+func buildForceDeregisterConfig(val, name string) string {
-	return fmt.Sprintf(testBuilderAccForceDeregister, name, flag)
+	return fmt.Sprintf(testBuilderAccForceDeregister, val, name)
+}
+
+func buildForceDeleteSnapshotConfig(val, name string) string {
+	return fmt.Sprintf(testBuilderAccForceDeleteSnapshot, val, val, name)
 }

builder/amazon/instance/builder.go

@@ -247,8 +247,9 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			Debug: b.config.PackerDebug,
 		},
 		&awscommon.StepDeregisterAMI{
-			ForceDeregister: b.config.AMIForceDeregister,
+			ForceDeregister:     b.config.AMIForceDeregister,
-			AMIName:         b.config.AMIName,
+			ForceDeleteSnapshot: b.config.AMIForceDeleteSnapshot,
+			AMIName:             b.config.AMIName,
 		},
 		&StepRegisterAMI{},
 		&awscommon.StepAMIRegionCopy{

website/source/docs/builders/amazon-chroot.html.md

@@ -124,6 +124,9 @@ each category, the available configuration keys are alphabetized.
 -   `force_deregister` (boolean) - Force Packer to first deregister an existing
     AMI if one with the same name already exists. Default `false`.
 
+-   `force_delete_snapshot` (boolean) - Force Packer to delete snapshots associated with
+    AMIs, which have been deregistered by `force_deregister`. Default `false`.
+
 -   `from_scratch` (boolean) - Build a new volume instead of starting from an
     existing AMI root volume snapshot. Default `false`. If true, `source_ami` is
     no longer used and the following options become required:

website/source/docs/builders/amazon-ebs.html.md

@@ -155,6 +155,9 @@ builder.
 -   `force_deregister` (boolean) - Force Packer to first deregister an existing
     AMI if one with the same name already exists. Default `false`.
 
+-   `force_delete_snapshot` (boolean) - Force Packer to delete snapshots associated with
+    AMIs, which have been deregistered by `force_deregister`. Default `false`.
+
 -   `encrypt_boot` (boolean) - Instruct packer to automatically create a copy of the
     AMI with an encrypted boot volume (discarding the initial unencrypted AMI in the
     process). Default `false`.

website/source/docs/builders/amazon-instance.html.md

@@ -179,6 +179,9 @@ builder.
 -   `force_deregister` (boolean) - Force Packer to first deregister an existing
     AMI if one with the same name already exists. Default `false`.
 
+-   `force_delete_snapshot` (boolean) - Force Packer to delete snapshots associated with
+    AMIs, which have been deregistered by `force_deregister`. Default `false`.
+
 -   `iam_instance_profile` (string) - The name of an [IAM instance
     profile](https://docs.aws.amazon.com/IAM/latest/UserGuide/instance-profiles.html)
     to launch the EC2 instance with.