builder/all: update to warnings

builder/digitalocean/builder.go

@@ -49,15 +49,15 @@ type Builder struct {
 	runner multistep.Runner
 }
 
-func (b *Builder) Prepare(raws ...interface{}) error {
+func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	md, err := common.DecodeConfig(&b.config, raws...)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	b.config.tpl, err = packer.NewConfigTemplate()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	b.config.tpl.UserVars = b.config.PackerUserVars
 
@@ -161,11 +161,11 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	b.config.stateTimeout = stateTimeout
 
 	if errs != nil && len(errs.Errors) > 0 {
-		return errs
+		return nil, errs
 	}
 
 	common.ScrubConfig(b.config, b.config.ClientID, b.config.APIKey)
-	return nil
+	return nil, nil
 }
 
 func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {

builder/digitalocean/builder_test.go

@@ -34,7 +34,10 @@ func TestBuilder_Prepare_BadType(t *testing.T) {
 		"api_key": []string{},
 	}
 
-	err := b.Prepare(c)
+	warnings, err := b.Prepare(c)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatalf("prepare should fail")
 	}
@@ -46,7 +49,10 @@ func TestBuilderPrepare_APIKey(t *testing.T) {
 
 	// Test good
 	config["api_key"] = "foo"
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -58,7 +64,10 @@ func TestBuilderPrepare_APIKey(t *testing.T) {
 	// Test bad
 	delete(config, "api_key")
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -67,7 +76,10 @@ func TestBuilderPrepare_APIKey(t *testing.T) {
 	delete(config, "api_key")
 	os.Setenv("DIGITALOCEAN_API_KEY", "foo")
 	defer os.Setenv("DIGITALOCEAN_API_KEY", "")
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -79,7 +91,10 @@ func TestBuilderPrepare_ClientID(t *testing.T) {
 
 	// Test good
 	config["client_id"] = "foo"
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -91,7 +106,10 @@ func TestBuilderPrepare_ClientID(t *testing.T) {
 	// Test bad
 	delete(config, "client_id")
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -100,7 +118,10 @@ func TestBuilderPrepare_ClientID(t *testing.T) {
 	delete(config, "client_id")
 	os.Setenv("DIGITALOCEAN_CLIENT_ID", "foo")
 	defer os.Setenv("DIGITALOCEAN_CLIENT_ID", "")
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -112,7 +133,10 @@ func TestBuilderPrepare_InvalidKey(t *testing.T) {
 
 	// Add a random key
 	config["i_should_not_be_valid"] = true
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -123,7 +147,10 @@ func TestBuilderPrepare_RegionID(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -135,7 +162,10 @@ func TestBuilderPrepare_RegionID(t *testing.T) {
 	// Test set
 	config["region_id"] = 2
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -150,7 +180,10 @@ func TestBuilderPrepare_SizeID(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -162,7 +195,10 @@ func TestBuilderPrepare_SizeID(t *testing.T) {
 	// Test set
 	config["size_id"] = 67
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -177,7 +213,10 @@ func TestBuilderPrepare_ImageID(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -189,7 +228,10 @@ func TestBuilderPrepare_ImageID(t *testing.T) {
 	// Test set
 	config["size_id"] = 2
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -204,7 +246,10 @@ func TestBuilderPrepare_SSHUsername(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -216,7 +261,10 @@ func TestBuilderPrepare_SSHUsername(t *testing.T) {
 	// Test set
 	config["ssh_username"] = "foo"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -231,7 +279,10 @@ func TestBuilderPrepare_SSHTimeout(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -243,7 +294,10 @@ func TestBuilderPrepare_SSHTimeout(t *testing.T) {
 	// Test set
 	config["ssh_timeout"] = "30s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -251,7 +305,10 @@ func TestBuilderPrepare_SSHTimeout(t *testing.T) {
 	// Test bad
 	config["ssh_timeout"] = "tubes"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -263,7 +320,10 @@ func TestBuilderPrepare_StateTimeout(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -275,7 +335,10 @@ func TestBuilderPrepare_StateTimeout(t *testing.T) {
 	// Test set
 	config["state_timeout"] = "5m"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -283,7 +346,10 @@ func TestBuilderPrepare_StateTimeout(t *testing.T) {
 	// Test bad
 	config["state_timeout"] = "tubes"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -295,7 +361,10 @@ func TestBuilderPrepare_SnapshotName(t *testing.T) {
 	config := testConfig()
 
 	// Test default
-	err := b.Prepare(config)
+	warnings, err := b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -307,7 +376,10 @@ func TestBuilderPrepare_SnapshotName(t *testing.T) {
 	// Test set
 	config["snapshot_name"] = "foobarbaz"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -315,7 +387,10 @@ func TestBuilderPrepare_SnapshotName(t *testing.T) {
 	// Test set with template
 	config["snapshot_name"] = "{{timestamp}}"
 	b = Builder{}
-	err = b.Prepare(config)
+	warnings, err = b.Prepare(config)
+	if len(warnings) > 0 {
+		t.Fatalf("bad: %#v", warnings)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}

builder/openstack/builder.go

@@ -29,15 +29,15 @@ type Builder struct {
 	runner multistep.Runner
 }
 
-func (b *Builder) Prepare(raws ...interface{}) error {
+func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	md, err := common.DecodeConfig(&b.config, raws...)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	b.config.tpl, err = packer.NewConfigTemplate()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	b.config.tpl.UserVars = b.config.PackerUserVars
 
@@ -48,11 +48,11 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	errs = packer.MultiErrorAppend(errs, b.config.RunConfig.Prepare(b.config.tpl)...)
 
 	if errs != nil && len(errs.Errors) > 0 {
-		return errs
+		return nil, errs
 	}
 
 	log.Println(common.ScrubConfig(b.config, b.config.Password))
-	return nil
+	return nil, nil
 }
 
 func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {

builder/openstack/builder_test.go

@@ -32,7 +32,10 @@ func TestBuilder_Prepare_BadType(t *testing.T) {
 		"password": []string{},
 	}
 
-	err := b.Prepare(c)
+	warns, err := b.Prepare(c)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatalf("prepare should fail")
 	}
@@ -44,7 +47,10 @@ func TestBuilderPrepare_ImageName(t *testing.T) {
 
 	// Test good
 	config["image_name"] = "foo"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -52,7 +58,10 @@ func TestBuilderPrepare_ImageName(t *testing.T) {
 	// Test bad
 	config["image_name"] = "foo {{"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -60,7 +69,10 @@ func TestBuilderPrepare_ImageName(t *testing.T) {
 	// Test bad
 	delete(config, "image_name")
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -72,7 +84,10 @@ func TestBuilderPrepare_InvalidKey(t *testing.T) {
 
 	// Add a random key
 	config["i_should_not_be_valid"] = true
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}

builder/virtualbox/builder.go

@@ -72,15 +72,15 @@ type config struct {
 	tpl             *packer.ConfigTemplate
 }
 
-func (b *Builder) Prepare(raws ...interface{}) error {
+func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	md, err := common.DecodeConfig(&b.config, raws...)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	b.config.tpl, err = packer.NewConfigTemplate()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	b.config.tpl.UserVars = b.config.PackerUserVars
 
@@ -364,10 +364,10 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	}
 
 	if errs != nil && len(errs.Errors) > 0 {
-		return errs
+		return nil, errs
 	}
 
-	return nil
+	return nil, nil
 }
 
 func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {

builder/virtualbox/builder_test.go

@@ -60,7 +60,10 @@ func TestBuilder_ImplementsBuilder(t *testing.T) {
 func TestBuilderPrepare_Defaults(t *testing.T) {
 	var b Builder
 	config := testConfig()
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -104,7 +107,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 
 	// Test a default boot_wait
 	delete(config, "boot_wait")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -115,7 +121,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 
 	// Test with a bad boot_wait
 	config["boot_wait"] = "this is not good"
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -123,7 +132,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 	// Test with a good one
 	config["boot_wait"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -134,7 +146,10 @@ func TestBuilderPrepare_DiskSize(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "disk_size")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -145,7 +160,10 @@ func TestBuilderPrepare_DiskSize(t *testing.T) {
 
 	config["disk_size"] = 60000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -160,7 +178,10 @@ func TestBuilderPrepare_FloppyFiles(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "floppy_files")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -171,7 +192,10 @@ func TestBuilderPrepare_FloppyFiles(t *testing.T) {
 
 	config["floppy_files"] = []string{"foo", "bar"}
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -188,7 +212,10 @@ func TestBuilderPrepare_GuestAdditionsMode(t *testing.T) {
 
 	// test default mode
 	delete(config, "guest_additions_mode")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -196,7 +223,10 @@ func TestBuilderPrepare_GuestAdditionsMode(t *testing.T) {
 	// Test another mode
 	config["guest_additions_mode"] = "attach"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -208,7 +238,10 @@ func TestBuilderPrepare_GuestAdditionsMode(t *testing.T) {
 	// Test bad mode
 	config["guest_additions_mode"] = "teleport"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should error")
 	}
@@ -219,7 +252,10 @@ func TestBuilderPrepare_GuestAdditionsPath(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "guest_additions_path")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -230,7 +266,10 @@ func TestBuilderPrepare_GuestAdditionsPath(t *testing.T) {
 
 	config["guest_additions_path"] = "foo"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -245,7 +284,10 @@ func TestBuilderPrepare_GuestAdditionsSHA256(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "guest_additions_sha256")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -256,7 +298,10 @@ func TestBuilderPrepare_GuestAdditionsSHA256(t *testing.T) {
 
 	config["guest_additions_sha256"] = "FOO"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -271,7 +316,10 @@ func TestBuilderPrepare_GuestAdditionsURL(t *testing.T) {
 	config := testConfig()
 
 	config["guest_additions_url"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -282,7 +330,10 @@ func TestBuilderPrepare_GuestAdditionsURL(t *testing.T) {
 
 	config["guest_additions_url"] = "http://www.packer.io"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Errorf("should not have error: %s", err)
 	}
@@ -294,7 +345,10 @@ func TestBuilderPrepare_HardDriveInterface(t *testing.T) {
 
 	// Test a default boot_wait
 	delete(config, "hard_drive_interface")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -306,7 +360,10 @@ func TestBuilderPrepare_HardDriveInterface(t *testing.T) {
 	// Test with a bad
 	config["hard_drive_interface"] = "fake"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -314,7 +371,10 @@ func TestBuilderPrepare_HardDriveInterface(t *testing.T) {
 	// Test with a good
 	config["hard_drive_interface"] = "sata"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -327,7 +387,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	// Bad
 	config["http_port_min"] = 1000
 	config["http_port_max"] = 500
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -335,7 +398,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	// Bad
 	config["http_port_min"] = -500
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -344,7 +410,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	config["http_port_min"] = 500
 	config["http_port_max"] = 1000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -356,7 +425,10 @@ func TestBuilderPrepare_Format(t *testing.T) {
 
 	// Bad
 	config["format"] = "illegal value"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -364,7 +436,10 @@ func TestBuilderPrepare_Format(t *testing.T) {
 	// Good
 	config["format"] = "ova"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -372,7 +447,10 @@ func TestBuilderPrepare_Format(t *testing.T) {
 	// Good
 	config["format"] = "ovf"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -384,7 +462,10 @@ func TestBuilderPrepare_InvalidKey(t *testing.T) {
 
 	// Add a random key
 	config["i_should_not_be_valid"] = true
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -396,7 +477,10 @@ func TestBuilderPrepare_ISOChecksum(t *testing.T) {
 
 	// Test bad
 	config["iso_checksum"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -404,7 +488,10 @@ func TestBuilderPrepare_ISOChecksum(t *testing.T) {
 	// Test good
 	config["iso_checksum"] = "FOo"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -420,7 +507,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 
 	// Test bad
 	config["iso_checksum_type"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -428,7 +518,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 	// Test good
 	config["iso_checksum_type"] = "mD5"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -440,7 +533,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 	// Test unknown
 	config["iso_checksum_type"] = "fake"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -455,7 +551,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	// Test both epty
 	config["iso_url"] = ""
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -463,7 +562,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	// Test iso_url set
 	config["iso_url"] = "http://www.packer.io"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Errorf("should not have error: %s", err)
 	}
@@ -477,7 +579,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	config["iso_url"] = "http://www.packer.io"
 	config["iso_urls"] = []string{"http://www.packer.io"}
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -490,7 +595,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	}
 
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Errorf("should not have error: %s", err)
 	}
@@ -517,7 +625,10 @@ func TestBuilderPrepare_OutputDir(t *testing.T) {
 
 	config["output_directory"] = dir
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -525,7 +636,10 @@ func TestBuilderPrepare_OutputDir(t *testing.T) {
 	// Test with a good one
 	config["output_directory"] = "i-hope-i-dont-exist"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -537,7 +651,10 @@ func TestBuilderPrepare_ShutdownTimeout(t *testing.T) {
 
 	// Test with a bad value
 	config["shutdown_timeout"] = "this is not good"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -545,7 +662,10 @@ func TestBuilderPrepare_ShutdownTimeout(t *testing.T) {
 	// Test with a good one
 	config["shutdown_timeout"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -559,7 +679,10 @@ func TestBuilderPrepare_SSHHostPort(t *testing.T) {
 	config["ssh_host_port_min"] = 1000
 	config["ssh_host_port_max"] = 500
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -567,7 +690,10 @@ func TestBuilderPrepare_SSHHostPort(t *testing.T) {
 	// Bad
 	config["ssh_host_port_min"] = -500
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -576,7 +702,10 @@ func TestBuilderPrepare_SSHHostPort(t *testing.T) {
 	config["ssh_host_port_min"] = 500
 	config["ssh_host_port_max"] = 1000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -588,14 +717,20 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 
 	config["ssh_key_path"] = ""
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
 
 	config["ssh_key_path"] = "/i/dont/exist"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -614,7 +749,10 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 
 	config["ssh_key_path"] = tf.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -625,7 +763,10 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 	tf.Write([]byte(testPem))
 	config["ssh_key_path"] = tf.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -637,14 +778,20 @@ func TestBuilderPrepare_SSHUser(t *testing.T) {
 
 	config["ssh_username"] = ""
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
 
 	config["ssh_username"] = "exists"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -656,7 +803,10 @@ func TestBuilderPrepare_SSHWaitTimeout(t *testing.T) {
 
 	// Test a default boot_wait
 	delete(config, "ssh_wait_timeout")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -668,7 +818,10 @@ func TestBuilderPrepare_SSHWaitTimeout(t *testing.T) {
 	// Test with a bad value
 	config["ssh_wait_timeout"] = "this is not good"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -676,7 +829,10 @@ func TestBuilderPrepare_SSHWaitTimeout(t *testing.T) {
 	// Test with a good one
 	config["ssh_wait_timeout"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -688,7 +844,10 @@ func TestBuilderPrepare_VBoxManage(t *testing.T) {
 
 	// Test with empty
 	delete(config, "vboxmanage")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -703,7 +862,10 @@ func TestBuilderPrepare_VBoxManage(t *testing.T) {
 	}
 
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -723,7 +885,10 @@ func TestBuilderPrepare_VBoxVersionFile(t *testing.T) {
 
 	// Test empty
 	delete(config, "virtualbox_version_file")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -735,7 +900,10 @@ func TestBuilderPrepare_VBoxVersionFile(t *testing.T) {
 	// Test with a good one
 	config["virtualbox_version_file"] = "foo"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}

builder/vmware/builder.go

@@ -66,15 +66,15 @@ type config struct {
 	tpl             *packer.ConfigTemplate
 }
 
-func (b *Builder) Prepare(raws ...interface{}) error {
+func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	md, err := common.DecodeConfig(&b.config, raws...)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	b.config.tpl, err = packer.NewConfigTemplate()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	b.config.tpl.UserVars = b.config.PackerUserVars
 
@@ -327,10 +327,10 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	}
 
 	if errs != nil && len(errs.Errors) > 0 {
-		return errs
+		return nil, errs
 	}
 
-	return nil
+	return nil, nil
 }
 
 func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {

builder/vmware/builder_test.go

@@ -64,7 +64,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 
 	// Test a default boot_wait
 	delete(config, "boot_wait")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -75,7 +78,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 
 	// Test with a bad boot_wait
 	config["boot_wait"] = "this is not good"
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -83,7 +89,10 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 	// Test with a good one
 	config["boot_wait"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -95,7 +104,10 @@ func TestBuilderPrepare_ISOChecksum(t *testing.T) {
 
 	// Test bad
 	config["iso_checksum"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -103,7 +115,10 @@ func TestBuilderPrepare_ISOChecksum(t *testing.T) {
 	// Test good
 	config["iso_checksum"] = "FOo"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -119,7 +134,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 
 	// Test bad
 	config["iso_checksum_type"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -127,7 +145,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 	// Test good
 	config["iso_checksum_type"] = "mD5"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -139,7 +160,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 	// Test unknown
 	config["iso_checksum_type"] = "fake"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -147,7 +171,10 @@ func TestBuilderPrepare_ISOChecksumType(t *testing.T) {
 func TestBuilderPrepare_Defaults(t *testing.T) {
 	var b Builder
 	config := testConfig()
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -174,7 +201,10 @@ func TestBuilderPrepare_DiskSize(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "disk_size")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -185,7 +215,10 @@ func TestBuilderPrepare_DiskSize(t *testing.T) {
 
 	config["disk_size"] = 60000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -200,7 +233,10 @@ func TestBuilderPrepare_FloppyFiles(t *testing.T) {
 	config := testConfig()
 
 	delete(config, "floppy_files")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -211,7 +247,10 @@ func TestBuilderPrepare_FloppyFiles(t *testing.T) {
 
 	config["floppy_files"] = []string{"foo", "bar"}
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -229,7 +268,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	// Bad
 	config["http_port_min"] = 1000
 	config["http_port_max"] = 500
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -237,7 +279,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	// Bad
 	config["http_port_min"] = -500
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -246,7 +291,10 @@ func TestBuilderPrepare_HTTPPort(t *testing.T) {
 	config["http_port_min"] = 500
 	config["http_port_max"] = 1000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -258,7 +306,10 @@ func TestBuilderPrepare_InvalidKey(t *testing.T) {
 
 	// Add a random key
 	config["i_should_not_be_valid"] = true
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -273,7 +324,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	// Test both epty
 	config["iso_url"] = ""
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -281,7 +335,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	// Test iso_url set
 	config["iso_url"] = "http://www.packer.io"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Errorf("should not have error: %s", err)
 	}
@@ -295,7 +352,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	config["iso_url"] = "http://www.packer.io"
 	config["iso_urls"] = []string{"http://www.packer.io"}
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -308,7 +368,10 @@ func TestBuilderPrepare_ISOUrl(t *testing.T) {
 	}
 
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Errorf("should not have error: %s", err)
 	}
@@ -335,7 +398,10 @@ func TestBuilderPrepare_OutputDir(t *testing.T) {
 
 	config["output_directory"] = dir
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -343,7 +409,10 @@ func TestBuilderPrepare_OutputDir(t *testing.T) {
 	// Test with a good one
 	config["output_directory"] = "i-hope-i-dont-exist"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -355,7 +424,10 @@ func TestBuilderPrepare_ShutdownTimeout(t *testing.T) {
 
 	// Test with a bad value
 	config["shutdown_timeout"] = "this is not good"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -363,7 +435,10 @@ func TestBuilderPrepare_ShutdownTimeout(t *testing.T) {
 	// Test with a good one
 	config["shutdown_timeout"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -375,14 +450,20 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 
 	config["ssh_key_path"] = ""
 	b = Builder{}
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
 
 	config["ssh_key_path"] = "/i/dont/exist"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -401,7 +482,10 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 
 	config["ssh_key_path"] = tf.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -412,7 +496,10 @@ func TestBuilderPrepare_sshKeyPath(t *testing.T) {
 	tf.Write([]byte(testPem))
 	config["ssh_key_path"] = tf.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -423,14 +510,20 @@ func TestBuilderPrepare_SSHUser(t *testing.T) {
 	config := testConfig()
 
 	config["ssh_username"] = ""
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
 
 	config["ssh_username"] = "exists"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -442,7 +535,10 @@ func TestBuilderPrepare_SSHPort(t *testing.T) {
 
 	// Test with a bad value
 	delete(config, "ssh_port")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("bad err: %s", err)
 	}
@@ -454,7 +550,10 @@ func TestBuilderPrepare_SSHPort(t *testing.T) {
 	// Test with a good one
 	config["ssh_port"] = 44
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -470,7 +569,10 @@ func TestBuilderPrepare_SSHWaitTimeout(t *testing.T) {
 
 	// Test with a bad value
 	config["ssh_wait_timeout"] = "this is not good"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -478,7 +580,10 @@ func TestBuilderPrepare_SSHWaitTimeout(t *testing.T) {
 	// Test with a good one
 	config["ssh_wait_timeout"] = "5s"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -490,7 +595,10 @@ func TestBuilderPrepare_ToolsUploadPath(t *testing.T) {
 
 	// Test a default
 	delete(config, "tools_upload_path")
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -502,7 +610,10 @@ func TestBuilderPrepare_ToolsUploadPath(t *testing.T) {
 	// Test with a bad value
 	config["tools_upload_path"] = "{{{nope}"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -510,7 +621,10 @@ func TestBuilderPrepare_ToolsUploadPath(t *testing.T) {
 	// Test with a good one
 	config["tools_upload_path"] = "hey"
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -522,7 +636,10 @@ func TestBuilderPrepare_VMXTemplatePath(t *testing.T) {
 
 	// Test bad
 	config["vmx_template_path"] = "/i/dont/exist/forreal"
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -541,7 +658,10 @@ func TestBuilderPrepare_VMXTemplatePath(t *testing.T) {
 
 	config["vmx_template_path"] = tf.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -560,7 +680,10 @@ func TestBuilderPrepare_VMXTemplatePath(t *testing.T) {
 
 	config["vmx_template_path"] = tf2.Name()
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -573,7 +696,10 @@ func TestBuilderPrepare_VNCPort(t *testing.T) {
 	// Bad
 	config["vnc_port_min"] = 1000
 	config["vnc_port_max"] = 500
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -581,7 +707,10 @@ func TestBuilderPrepare_VNCPort(t *testing.T) {
 	// Bad
 	config["vnc_port_min"] = -500
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err == nil {
 		t.Fatal("should have error")
 	}
@@ -590,7 +719,10 @@ func TestBuilderPrepare_VNCPort(t *testing.T) {
 	config["vnc_port_min"] = 500
 	config["vnc_port_max"] = 1000
 	b = Builder{}
-	err = b.Prepare(config)
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
@@ -605,7 +737,10 @@ func TestBuilderPrepare_VMXData(t *testing.T) {
 		"two": "bar",
 	}
 
-	err := b.Prepare(config)
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}