packer: Add errors to Prepare

packer/plugin/provisioner.go

@@ -13,13 +13,13 @@ type cmdProvisioner struct {
 	client *client
 }
 
-func (c *cmdProvisioner) Prepare(configs ...interface{}) {
+func (c *cmdProvisioner) Prepare(configs ...interface{}) error {
 	defer func() {
 		r := recover()
 		c.checkExit(r, nil)
 	}()
 
-	c.p.Prepare(configs...)
+	return c.p.Prepare(configs...)
 }
 
 func (c *cmdProvisioner) Provision(ui packer.Ui, comm packer.Communicator) {

packer/plugin/provisioner_test.go

@@ -9,7 +9,9 @@ import (
 
 type helperProvisioner byte
 
-func (helperProvisioner) Prepare(...interface{}) {}
+func (helperProvisioner) Prepare(...interface{}) error {
+	return nil
+}
 
 func (helperProvisioner) Provision(packer.Ui, packer.Communicator) {}
 

packer/provisioner.go

@@ -6,7 +6,7 @@ type Provisioner interface {
 	// Prepare is called with a set of configurations to setup the
 	// internal state of the provisioner. The multiple configurations
 	// should be merged in some sane way.
-	Prepare(...interface{})
+	Prepare(...interface{}) error
 
 	// Provision is called to actually provision the machine. A UI is
 	// given to communicate with the user, and a communicator is given that

packer/provisioner_test.go

@@ -8,9 +8,10 @@ type TestProvisioner struct {
 	provCalled bool
 }
 
-func (t *TestProvisioner) Prepare(configs ...interface{}) {
+func (t *TestProvisioner) Prepare(configs ...interface{}) error {
 	t.prepCalled = true
 	t.prepConfigs = configs
+	return nil
 }
 
 func (t *TestProvisioner) Provision(Ui, Communicator) {

packer/rpc/provisioner.go

@@ -28,9 +28,13 @@ type ProvisionerProvisionArgs struct {
 func Provisioner(client *rpc.Client) *provisioner {
 	return &provisioner{client}
 }
-func (p *provisioner) Prepare(configs ...interface{}) {
+func (p *provisioner) Prepare(configs ...interface{}) (err error) {
 	args := &ProvisionerPrepareArgs{configs}
-	p.client.Call("Provisioner.Prepare", args, new(interface{}))
+	if cerr := p.client.Call("Provisioner.Prepare", args, &err); cerr != nil {
+		err = cerr
+	}
+
+	return
 }
 
 func (p *provisioner) Provision(ui packer.Ui, comm packer.Communicator) {
@@ -43,8 +47,8 @@ func (p *provisioner) Provision(ui packer.Ui, comm packer.Communicator) {
 	p.client.Call("Provisioner.Provision", args, new(interface{}))
 }
 
-func (p *ProvisionerServer) Prepare(args *ProvisionerPrepareArgs, reply *interface{}) error {
-	p.p.Prepare(args.Configs...)
+func (p *ProvisionerServer) Prepare(args *ProvisionerPrepareArgs, reply *error) error {
+	*reply = p.p.Prepare(args.Configs...)
 	return nil
 }
 

packer/rpc/provisioner_test.go

@@ -15,9 +15,10 @@ type testProvisioner struct {
 	provUi        packer.Ui
 }
 
-func (p *testProvisioner) Prepare(configs ...interface{}) {
+func (p *testProvisioner) Prepare(configs ...interface{}) error {
 	p.prepareCalled = true
 	p.prepareConfigs = configs
+	return nil
 }
 
 func (p *testProvisioner) Provision(ui packer.Ui, comm packer.Communicator) {

provisioner/shell/provisioner.go

@@ -29,15 +29,19 @@ type Provisioner struct {
 	config config
 }
 
-func (p *Provisioner) Prepare(raws ...interface{}) {
+func (p *Provisioner) Prepare(raws ...interface{}) error {
 	// TODO: errors
 	for _, raw := range raws {
-		_ = mapstructure.Decode(raw, &p.config)
+		if err := mapstructure.Decode(raw, &p.config); err != nil {
+			return err
+		}
 	}
 
 	if p.config.RemotePath == "" {
 		p.config.RemotePath = DefaultRemotePath
 	}
+
+	return nil
 }
 
 func (p *Provisioner) Provision(ui packer.Ui, comm packer.Communicator) {

provisioner/shell/provisioner_test.go

@@ -17,7 +17,10 @@ func TestProvisionerPrepare_Defaults(t *testing.T) {
 	raw := map[string]interface{}{}
 
 	p := &Provisioner{}
-	p.Prepare(raw, nil)
+	err := p.Prepare(raw)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
 
 	if p.config.RemotePath != DefaultRemotePath {
 		t.Errorf("unexpected remote path: %s", p.config.RemotePath)