packer: Build.Prepare takes a UI

command/build/command.go

@@ -64,7 +64,7 @@ func (Command) Run(env packer.Environment, args []string) int {
 	// Prepare all the builds
 	for _, b := range builds {
 		log.Printf("Preparing build: %s", b.Name())
-		err := b.Prepare()
+		err := b.Prepare(buildUis[b.Name()])
 		if err != nil {
 			env.Ui().Error(err.Error())
 			return 1

packer/build.go

@@ -6,7 +6,7 @@ import "log"
 // building some machine image artifact. Builds are meant to be parallelized.
 type Build interface {
 	Name() string
-	Prepare() error
+	Prepare(Ui) error
 	Run(Ui) Artifact
 }
 
@@ -38,7 +38,7 @@ func (b *coreBuild) Name() string {
 
 // Prepare prepares the build by doing some initialization for the builder
 // and any hooks. This _must_ be called prior to Run.
-func (b *coreBuild) Prepare() (err error) {
+func (b *coreBuild) Prepare(ui Ui) (err error) {
 	b.prepareCalled = true
 	err = b.builder.Prepare(b.builderConfig)
 	if err != nil {

packer/build_test.go

@@ -51,7 +51,7 @@ func TestBuild_Prepare(t *testing.T) {
 	build := testBuild()
 	builder := build.(*coreBuild).builder.(*TestBuilder)
 
-	build.Prepare()
+	build.Prepare(nil)
 	assert.True(builder.prepareCalled, "prepare should be called")
 	assert.Equal(builder.prepareConfig, 42, "prepare config should be 42")
 }
@@ -62,7 +62,7 @@ func TestBuild_Run(t *testing.T) {
 	ui := testUi()
 
 	build := testBuild()
-	build.Prepare()
+	build.Prepare(ui)
 	build.Run(ui)
 
 	builder := build.(*coreBuild).builder.(*TestBuilder)

packer/rpc/build.go

@@ -17,7 +17,9 @@ type BuildServer struct {
 	build packer.Build
 }
 
-type BuildPrepareArgs interface{}
+type BuildPrepareArgs struct {
+	RPCAddress string
+}
 
 type BuildRunArgs struct {
 	UiRPCAddress string
@@ -32,8 +34,17 @@ func (b *build) Name() (result string) {
 	return
 }
 
-func (b *build) Prepare() (err error) {
+func (b *build) Prepare(ui packer.Ui) (err error) {
-	b.client.Call("Build.Prepare", new(interface{}), &err)
+	// Create and start the server for the UI
+	// TODO: Error handling
+	server := rpc.NewServer()
+	RegisterUi(server, ui)
+	args := &BuildPrepareArgs{serveSingleConn(server)}
+
+	if err := b.client.Call("Build.Prepare", args, &err); err != nil {
+		panic(err)
+	}
+
 	return
 }
 
@@ -63,7 +74,12 @@ func (b *BuildServer) Name(args *interface{}, reply *string) error {
 }
 
 func (b *BuildServer) Prepare(args *BuildPrepareArgs, reply *error) error {
-	*reply = b.build.Prepare()
+	client, err := rpc.Dial("tcp", args.RPCAddress)
+	if err != nil {
+		return err
+	}
+
+	*reply = b.build.Prepare(&Ui{client})
 	return nil
 }
 

packer/rpc/build_test.go

@@ -12,6 +12,7 @@ var testBuildArtifact = &testArtifact{}
 type testBuild struct {
 	nameCalled    bool
 	prepareCalled bool
+	prepareUi packer.Ui
 	runCalled     bool
 	runUi         packer.Ui
 }
@@ -21,8 +22,9 @@ func (b *testBuild) Name() string {
 	return "name"
 }
 
-func (b *testBuild) Prepare() error {
+func (b *testBuild) Prepare(ui packer.Ui) error {
 	b.prepareCalled = true
+	b.prepareUi = ui
 	return nil
 }
 
@@ -53,11 +55,12 @@ func TestBuildRPC(t *testing.T) {
 	assert.True(b.nameCalled, "name should be called")
 
 	// Test Prepare
-	bClient.Prepare()
+	ui := new(testUi)
+	bClient.Prepare(ui)
 	assert.True(b.prepareCalled, "prepare should be called")
 
 	// Test Run
-	ui := new(testUi)
+	ui = new(testUi)
 	bClient.Run(ui)
 	assert.True(b.runCalled, "run should be called")