fix: make ResponseMessage.Result omitzero (#1533)

Co-authored-by: Jake Bailey <[email protected]>

Author: skewb1k

internal/lsp/lsproto/_generate/generate.mts

@@ -704,10 +704,16 @@ function generateCode() {
             }
 
             writeLine(`// Response type for \`${request.method}\``);
-            const resultType = resolveType(request.result);
-            const goType = resultType.needsPointer ? `*${resultType.name}` : resultType.name;
 
-            writeLine(`type ${responseTypeName} = ${goType}`);
+            // Special case for response types that are explicitly base type "null"
+            if (request.result.kind === "base" && request.result.name === "null") {
+                writeLine(`type ${responseTypeName} = Null`);
+            }
+            else {
+                const resultType = resolveType(request.result);
+                const goType = resultType.needsPointer ? `*${resultType.name}` : resultType.name;
+                writeLine(`type ${responseTypeName} = ${goType}`);
+            }
             writeLine("");
         }
 

internal/lsp/lsproto/jsonrpc.go

@@ -207,7 +207,7 @@ func (r *RequestMessage) UnmarshalJSON(data []byte) error {
 type ResponseMessage struct {
 	JSONRPC JSONRPCVersion `json:"jsonrpc"`
 	ID      *ID            `json:"id,omitzero"`
-	Result  any            `json:"result"`
+	Result  any            `json:"result,omitzero"`
 	Error   *ResponseError `json:"error,omitzero"`
 }
 

internal/lsp/lsproto/lsp.go

@@ -83,3 +83,20 @@ type NotificationInfo[Params any] struct {
 	_      [0]Params
 	Method Method
 }
+
+type Null struct{}
+
+func (Null) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	data, err := dec.ReadValue()
+	if err != nil {
+		return err
+	}
+	if string(data) != "null" {
+		return fmt.Errorf("expected null, got %s", data)
+	}
+	return nil
+}
+
+func (Null) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return enc.WriteToken(jsontext.Null)
+}

internal/lsp/lsproto/lsp_generated.go

@@ -660,7 +660,7 @@ func (s *Server) handleInitialized(ctx context.Context, params *lsproto.Initiali
 
 func (s *Server) handleShutdown(ctx context.Context, params any) (lsproto.ShutdownResponse, error) {
 	s.projectService.Close()
-	return nil, nil
+	return lsproto.ShutdownResponse{}, nil
 }
 
 func (s *Server) handleExit(ctx context.Context, params any) error {