fix: support source and sink func declarations

buildengine/build_go_test.go

@@ -36,6 +36,23 @@ func TestGenerateGoModule(t *testing.T) {
 					Request:  &schema.Ref{Name: "EchoRequest"},
 					Response: &schema.Ref{Name: "EchoResponse"},
 				},
+				&schema.Data{Name: "SinkReq"},
+				&schema.Verb{
+					Name:     "sink",
+					Request:  &schema.Ref{Name: "SinkReq"},
+					Response: &schema.Unit{},
+				},
+				&schema.Data{Name: "SourceResp"},
+				&schema.Verb{
+					Name:     "source",
+					Request:  &schema.Unit{},
+					Response: &schema.Ref{Name: "SourceResp"},
+				},
+				&schema.Verb{
+					Name:     "nothing",
+					Request:  &schema.Unit{},
+					Response: &schema.Unit{},
+				},
 			}},
 			{Name: "test"},
 		},
@@ -77,6 +94,27 @@ type EchoResponse struct {
 func Echo(context.Context, EchoRequest) (EchoResponse, error) {
   panic("Verb stubs should not be called directly, instead use github.com/TBD54566975/ftl/runtime-go/ftl.Call()")
 }
+
+type SinkReq struct {
+}
+
+//ftl:verb
+func Sink(context.Context, SinkReq) error {
+  panic("Verb stubs should not be called directly, instead use github.com/TBD54566975/ftl/runtime-go/ftl.CallSink()")
+}
+
+type SourceResp struct {
+}
+
+//ftl:verb
+func Source(context.Context) (SourceResp, error) {
+  panic("Verb stubs should not be called directly, instead use github.com/TBD54566975/ftl/runtime-go/ftl.CallSource()")
+}
+
+//ftl:verb
+func Nothing(context.Context) error {
+  panic("Verb stubs should not be called directly, instead use github.com/TBD54566975/ftl/runtime-go/ftl.CallEmpty()")
+}
 `
 	bctx := buildContext{
 		moduleDir: "testdata/modules/another",

buildengine/build_kotlin_test.go

@@ -305,3 +305,81 @@ fun emptyVerb(context: Context, req: ftl.builtin.Empty): ftl.builtin.Empty = thr
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
+
+func TestGenerateSourcesAndSinks(t *testing.T) {
+	if testing.Short() {
+		t.SkipNow()
+	}
+	sch := &schema.Schema{
+		Modules: []*schema.Module{
+			schema.Builtins(),
+			{
+				Name: "test",
+				Decls: []schema.Decl{
+					&schema.Data{
+						Name: "SinkReq",
+						Fields: []*schema.Field{
+							{Name: "data", Type: &schema.Int{}},
+						}},
+					&schema.Verb{
+						Name:     "sink",
+						Request:  &schema.Ref{Name: "SinkReq"},
+						Response: &schema.Unit{},
+					},
+					&schema.Data{
+						Name: "SourceResp",
+						Fields: []*schema.Field{
+							{Name: "data", Type: &schema.Int{}},
+						}},
+					&schema.Verb{
+						Name:     "source",
+						Request:  &schema.Unit{},
+						Response: &schema.Ref{Name: "SourceResp"},
+					},
+					&schema.Verb{
+						Name:     "nothing",
+						Request:  &schema.Unit{},
+						Response: &schema.Unit{},
+					},
+				},
+			},
+		},
+	}
+
+	expected := `// Code generated by FTL. DO NOT EDIT.
+package ftl.test
+
+import xyz.block.ftl.Context
+import xyz.block.ftl.Ignore
+import xyz.block.ftl.Verb
+
+data class SinkReq(
+  val data: Long,
+)
+
+@Verb
+@Ignore
+fun sink(context: Context, req: SinkReq): Unit = throw
+    NotImplementedError("Verb stubs should not be called directly, instead use context.callSink(::sink, ...)")
+data class SourceResp(
+  val data: Long,
+)
+
+@Verb
+@Ignore
+fun source(context: Context): SourceResp = throw
+    NotImplementedError("Verb stubs should not be called directly, instead use context.callSource(::source, ...)")
+@Verb
+@Ignore
+fun nothing(context: Context): Unit = throw
+    NotImplementedError("Verb stubs should not be called directly, instead use context.callEmpty(::nothing, ...)")
+`
+	bctx := buildContext{
+		moduleDir: "testdata/modules/echokotlin",
+		buildDir:  "target",
+		sch:       sch,
+	}
+	testBuild(t, bctx, []assertion{
+		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
+	})
+}

examples/go/echo/echo.go

@@ -27,10 +27,10 @@ type EchoResponse struct {
 //
 //ftl:verb
 func Echo(ctx context.Context, req EchoRequest) (EchoResponse, error) {
-	fmt.Println("Echo received a request!")
 	tresp, err := ftl.Call(ctx, time.Time, time.TimeRequest{})
 	if err != nil {
 		return EchoResponse{}, err
 	}
+
 	return EchoResponse{Message: fmt.Sprintf("Hello, %s!!! It is %s!", req.Name.Default(defaultName.Get(ctx)), tresp.Time)}, nil
 }

go-runtime/compile/build.go

@@ -34,7 +34,9 @@ type externalModuleContext struct {
 }
 
 type goVerb struct {
-	Name string
+	Name        string
+	HasRequest  bool
+	HasResponse bool
 }
 
 type mainModuleContext struct {
@@ -122,7 +124,15 @@ func Build(ctx context.Context, moduleDir string, sch *schema.Schema) error {
 			if !ok {
 				return fmt.Errorf("missing native name for verb %s", verb.Name)
 			}
-			goVerbs = append(goVerbs, goVerb{Name: nativeName})
+
+			goverb := goVerb{Name: nativeName}
+			if _, ok := verb.Request.(*schema.Unit); !ok {
+				goverb.HasRequest = true
+			}
+			if _, ok := verb.Response.(*schema.Unit); !ok {
+				goverb.HasResponse = true
+			}
+			goVerbs = append(goVerbs, goverb)
 		}
 	}
 	if err := internal.ScaffoldZip(buildTemplateFiles(), moduleDir, mainModuleContext{
@@ -183,7 +193,7 @@ var scaffoldFuncs = scaffolder.FuncMap{
 			case *schema.Time:
 				imports["time"] = "stdtime"
 
-			case *schema.Optional, *schema.Unit:
+			case *schema.Optional:
 				imports["github.com/TBD54566975/ftl/go-runtime/ftl"] = ""
 
 			default:

go-runtime/compile/schema.go

@@ -30,11 +30,12 @@ var (
 	errorIFaceType = once(func() *types.Interface {
 		return mustLoadRef("builtin", "error").Type().Underlying().(*types.Interface) //nolint:forcetypeassert
 	})
+
 	ftlCallFuncPath   = "github.com/TBD54566975/ftl/go-runtime/ftl.Call"
 	ftlConfigFuncPath = "github.com/TBD54566975/ftl/go-runtime/ftl.Config"
 	ftlSecretFuncPath = "github.com/TBD54566975/ftl/go-runtime/ftl.Secret" //nolint:gosec
-
-	aliasFieldTag = "json"
+	ftlUnitTypePath   = "github.com/TBD54566975/ftl/go-runtime/ftl.Unit"
+	aliasFieldTag     = "json"
 )
 
 // NativeNames is a map of top-level declarations to their native Go names.
@@ -269,6 +270,10 @@ func checkSignature(sig *types.Signature) (req, resp *types.Var, err error) {
 		if !isType[*types.Struct](params.At(1).Type()) {
 			return nil, nil, fmt.Errorf("second parameter must be a struct but is %s", params.At(1).Type())
 		}
+		if params.At(1).Type().String() == ftlUnitTypePath {
+			return nil, nil, fmt.Errorf("second parameter must not be ftl.Unit")
+		}
+
 		req = params.At(1)
 	}
 
@@ -285,11 +290,11 @@ func checkSignature(sig *types.Signature) (req, resp *types.Var, err error) {
 		if !isType[*types.Struct](results.At(0).Type()) {
 			return nil, nil, fmt.Errorf("first result must be a struct but is %s", results.At(0).Type())
 		}
+		if results.At(1).Type().String() == ftlUnitTypePath {
+			return nil, nil, fmt.Errorf("first result must not be ftl.Unit")
+		}
 		resp = results.At(0)
 	}
-	if params.Len() == 1 && results.Len() == 1 {
-		return nil, nil, fmt.Errorf("must either accept an input or return a result, but does neither")
-	}
 	return req, resp, nil
 }
 

go-runtime/compile/schema_test.go

@@ -47,6 +47,12 @@ func TestExtractModuleSchema(t *testing.T) {
   data Resp {
   }
 
+  data SinkReq {
+  }
+
+  data SourceResp {
+  }
+
   enum Color(String) {
     Red("Red")
     Blue("Blue")
@@ -75,6 +81,12 @@ func TestExtractModuleSchema(t *testing.T) {
 
   secret secretValue String
 
+  verb nothing(Unit) Unit
+
+  verb sink(one.SinkReq) Unit
+
+  verb source(Unit) one.SourceResp
+
   verb verb(one.Req) one.Resp
 }
 `

go-runtime/compile/testdata/one/one.go

@@ -79,3 +79,22 @@ func Verb(ctx context.Context, req Req) (Resp, error) {
 const Yellow Color = "Yellow"
 
 const YellowInt ColorInt = 3
+
+type SinkReq struct{}
+
+//ftl:verb
+func Sink(ctx context.Context, req SinkReq) error {
+	return nil
+}
+
+type SourceResp struct{}
+
+//ftl:verb
+func Source(ctx context.Context) (SourceResp, error) {
+	return SourceResp{}, nil
+}
+
+//ftl:verb
+func Nothing(ctx context.Context) error {
+	return nil
+}

go-runtime/ftl/call.go

@@ -11,20 +11,19 @@ import (
 
 	ftlv1 "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1"
 	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/ftlv1connect"
+	schemapb "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/schema"
 	"github.com/TBD54566975/ftl/backend/schema/strcase"
 	"github.com/TBD54566975/ftl/go-runtime/encoding"
 	"github.com/TBD54566975/ftl/internal/rpc"
 )
 
-// Call a Verb through the FTL Controller.
-func Call[Req, Resp any](ctx context.Context, verb Verb[Req, Resp], req Req) (resp Resp, err error) {
-	callee := VerbToRef(verb)
+func call[Req, Resp any](ctx context.Context, callee *schemapb.Ref, req Req) (resp Resp, err error) {
 	client := rpc.ClientFromContext[ftlv1connect.VerbServiceClient](ctx)
 	reqData, err := encoding.Marshal(req)
 	if err != nil {
 		return resp, fmt.Errorf("%s: failed to marshal request: %w", callee, err)
 	}
-	cresp, err := client.Call(ctx, connect.NewRequest(&ftlv1.CallRequest{Verb: callee.ToProto(), Body: reqData}))
+	cresp, err := client.Call(ctx, connect.NewRequest(&ftlv1.CallRequest{Verb: callee, Body: reqData}))
 	if err != nil {
 		return resp, fmt.Errorf("%s: failed to call Verb: %w", callee, err)
 	}
@@ -44,21 +43,40 @@ func Call[Req, Resp any](ctx context.Context, verb Verb[Req, Resp], req Req) (re
 	}
 }
 
-// Call a Sink through the FTL controller.
-// func CallSink[Req any](ctx context.Context, sink Sink[Req]) error {
-// }
+// Call a Verb through the FTL Controller.
+func Call[Req, Resp any](ctx context.Context, verb Verb[Req, Resp], req Req) (Resp, error) {
+	return call[Req, Resp](ctx, CallToSchemaRef(verb), req)
+}
 
-// VerbToRef returns the FTL reference for a Verb.
-func VerbToRef[Req, Resp any](verb Verb[Req, Resp]) Ref {
-	ref := runtime.FuncForPC(reflect.ValueOf(verb).Pointer()).Name()
-	return goRefToFTLRef(ref)
+// CallSink calls a Sink through the FTL controller.
+func CallSink[Req any](ctx context.Context, sink Sink[Req], req Req) error {
+	_, err := call[Req, Unit](ctx, CallToSchemaRef(sink), req)
+	return err
+}
+
+// CallSource calls a Source through the FTL controller.
+func CallSource[Resp any](ctx context.Context, source Source[Resp]) (Resp, error) {
+	return call[Unit, Resp](ctx, CallToSchemaRef(source), Unit{})
+}
+
+// CallEmpty calls a Verb with no request or response through the FTL controller.
+func CallEmpty(ctx context.Context, empty Empty) error {
+	_, err := call[Unit, Unit](ctx, CallToSchemaRef(empty), Unit{})
+	return err
 }
 
-func SinkToRef[Req any](sink Sink[Req]) Ref {
-	ref := runtime.FuncForPC(reflect.ValueOf(sink).Pointer()).Name()
+// CallToRef returns the Ref for a Verb, Sink, Source, or Empty.
+func CallToRef(call any) Ref {
+	ref := runtime.FuncForPC(reflect.ValueOf(call).Pointer()).Name()
 	return goRefToFTLRef(ref)
 }
 
+// CallToSchemaRef returns the Ref for a Verb, Sink, Source, or Empty as a Schema Ref.
+func CallToSchemaRef(call any) *schemapb.Ref {
+	ref := CallToRef(call)
+	return ref.ToProto()
+}
+
 func goRefToFTLRef(ref string) Ref {
 	parts := strings.Split(ref[strings.LastIndex(ref, "/")+1:], ".")
 	return Ref{parts[len(parts)-2], strcase.ToLowerCamel(parts[len(parts)-1])}