packer/rpc: Builders return valid artifacts

packer/rpc/builder.go

@@ -46,10 +46,18 @@ func (b *builder) Run(ui packer.Ui, hook packer.Hook) packer.Artifact {
 	RegisterHook(server, hook)
 
 	args := &BuilderRunArgs{serveSingleConn(server)}
-	b.client.Call("Builder.Run", args, new(interface{}))
 
-	// TODO: artifact
-	return nil
+	var reply string
+	if err := b.client.Call("Builder.Run", args, &reply); err != nil {
+		panic(err)
+	}
+
+	client, err := rpc.Dial("tcp", reply)
+	if err != nil {
+		panic(err)
+	}
+
+	return Artifact(client)
 }
 
 func (b *BuilderServer) Prepare(args *BuilderPrepareArgs, reply *error) error {
@@ -61,7 +69,7 @@ func (b *BuilderServer) Prepare(args *BuilderPrepareArgs, reply *error) error {
 	return nil
 }
 
-func (b *BuilderServer) Run(args *BuilderRunArgs, reply *interface{}) error {
+func (b *BuilderServer) Run(args *BuilderRunArgs, reply *string) error {
 	client, err := rpc.Dial("tcp", args.RPCAddress)
 	if err != nil {
 		return err
@@ -69,8 +77,12 @@ func (b *BuilderServer) Run(args *BuilderRunArgs, reply *interface{}) error {
 
 	hook := Hook(client)
 	ui := &Ui{client}
-	b.builder.Run(ui, hook)
+	artifact := b.builder.Run(ui, hook)
 
-	*reply = nil
+	// Wrap the artifact
+	server := rpc.NewServer()
+	RegisterArtifact(server, artifact)
+
+	*reply = serveSingleConn(server)
 	return nil
 }

packer/rpc/builder_test.go

@@ -7,6 +7,8 @@ import (
 	"testing"
 )
 
+var testBuilderArtifact = &testArtifact{}
+
 type testBuilder struct {
 	prepareCalled bool
 	prepareConfig interface{}
@@ -25,7 +27,7 @@ func (b *testBuilder) Run(ui packer.Ui, hook packer.Hook) packer.Artifact {
 	b.runCalled = true
 	b.runHook = hook
 	b.runUi = ui
-	return nil
+	return testBuilderArtifact
 }
 
 func TestBuilderRPC(t *testing.T) {
@@ -53,7 +55,7 @@ func TestBuilderRPC(t *testing.T) {
 	// Test Run
 	hook := &testHook{}
 	ui := &testUi{}
-	bClient.Run(ui, hook)
+	artifact := bClient.Run(ui, hook)
 	assert.True(b.runCalled, "runs hould be called")
 
 	if b.runCalled {
@@ -63,6 +65,8 @@ func TestBuilderRPC(t *testing.T) {
 		b.runUi.Say("format")
 		assert.True(ui.sayCalled, "say should be called")
 		assert.Equal(ui.sayFormat, "format", "format should be correct")
+
+		assert.Equal(artifact.Id(), testBuilderArtifact.Id(), "should have artifact Id")
 	}
 }