prevent creating rust bindings if they're not needed

cmd/substreams/build.go

@@ -60,7 +60,9 @@ func runBuildE(cmd *cobra.Command, args []string) error {
 		Manifest: manif,
 	}
 
-	protoBuilder, err := newProtoBuilder(info)
+	binaryLabel := sflags.MustGetString(cmd, "binary")
+
+	protoBuilder, err := newProtoBuilder(info, binaryLabel)
 	if err != nil {
 		return fmt.Errorf("error creating proto builder: %w", err)
 	}
@@ -69,8 +71,6 @@ func runBuildE(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("error running protogen: %w", err)
 	}
 
-	binaryLabel := sflags.MustGetString(cmd, "binary")
-
 	binaryBuilder, err := newBinaryBuilder(info, binaryLabel)
 	if err != nil {
 		return fmt.Errorf("error creating binary builder: %w", err)
@@ -125,16 +125,24 @@ type manifestInfo struct {
 }
 
 type ProtoBuilder struct {
-	manifInfo *manifestInfo
+	manifInfo   *manifestInfo
+	binaryLabel string
 }
 
-func newProtoBuilder(manifInfo *manifestInfo) (*ProtoBuilder, error) {
+func newProtoBuilder(manifInfo *manifestInfo, binaryLabel string) (*ProtoBuilder, error) {
 	return &ProtoBuilder{
-		manifInfo: manifInfo,
+		manifInfo:   manifInfo,
+		binaryLabel: binaryLabel,
 	}, nil
 }
 
 func (p *ProtoBuilder) Build(ctx context.Context) error {
+
+	if len(p.manifInfo.Manifest.Binaries) == 0 || !strings.HasPrefix(p.manifInfo.Manifest.Binaries[p.binaryLabel].Type, "wasm/rust-v1") {
+		fmt.Println("Notice: No binaries found of type `wasm/rust-v1`, not generating rust bindings...")
+		return nil
+	}
+
 	excludes := strings.Join(p.manifInfo.Manifest.Protobuf.ExcludePaths, ",")
 	if excludes == "" {
 		fmt.Printf("Notice: No exclude paths found:\n")

codegen/helpers.go

@@ -126,9 +126,15 @@ func buildGenerateCommandFromArgs(manifestPath string, outputType OutputType, wi
 		moduleNames = append(moduleNames, module.Name)
 	}
 
-	selectedModule, err := createSelectForm(moduleNames, "Please select a mapper module to build the subgraph from:")
-	if err != nil {
-		return fmt.Errorf("creating request module form: %w", err)
+	var selectedModule string
+	if len(moduleNames) == 1 {
+		selectedModule = moduleNames[0]
+		fmt.Printf("\nThe substreams module %q will be used as output.\n\n", selectedModule)
+	} else {
+		selectedModule, err = createSelectForm(moduleNames, "Please select a mapper module to build the subgraph from:")
+		if err != nil {
+			return fmt.Errorf("creating request module form: %w", err)
+		}
 	}
 
 	requestedModule, err := getModule(pkg, selectedModule)