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fix: write back error message if the response marshal failed #235

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Merged
merged 1 commit into from
May 2, 2025
Merged

fix: write back error message if the response marshal failed #235

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2 changes: 0 additions & 2 deletions server/sse.go
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Original file line number Diff line number Diff line change
Expand Up @@ -457,15 +457,13 @@ func (s *SSEServer) handleMessage(w http.ResponseWriter, r *http.Request) {
go func() {
// Process message through MCPServer
response := s.server.HandleMessage(ctx, rawMessage)

// Only send response if there is one (not for notifications)
if response != nil {
var message string
if eventData, err := json.Marshal(response); err != nil {
// If there is an error marshalling the response, send a generic error response
log.Printf("failed to marshal response: %v", err)
message = fmt.Sprintf("event: message\ndata: {\"error\": \"internal error\",\"jsonrpc\": \"2.0\", \"id\": null}\n\n")
return
} else {
message = fmt.Sprintf("event: message\ndata: %s\n\n", eventData)
}
Expand Down
102 changes: 90 additions & 12 deletions server/sse_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,7 @@ func TestSSEServer(t *testing.T) {
defer sseResp.Body.Close()

// Read the endpoint event
endpointEvent, err := readSeeEvent(sseResp)
endpointEvent, err := readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
Expand Down Expand Up @@ -195,7 +195,7 @@ func TestSSEServer(t *testing.T) {
}
defer resp.Body.Close()

endpointEvent, err = readSeeEvent(sseResp)
endpointEvent, err = readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
Expand Down Expand Up @@ -590,7 +590,7 @@ func TestSSEServer(t *testing.T) {
defer sseResp.Body.Close()

// Read the endpoint event
endpointEvent, err := readSeeEvent(sseResp)
endpointEvent, err := readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
Expand Down Expand Up @@ -632,16 +632,16 @@ func TestSSEServer(t *testing.T) {
}

// Verify response
endpointEvent, err = readSeeEvent(sseResp)
endpointEvent, err = readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
respFromSee := strings.TrimSpace(
respFromSSE := strings.TrimSpace(
strings.Split(strings.Split(endpointEvent, "data: ")[1], "\n")[0],
)

var response map[string]interface{}
if err := json.NewDecoder(strings.NewReader(respFromSee)).Decode(&response); err != nil {
if err := json.NewDecoder(strings.NewReader(respFromSSE)).Decode(&response); err != nil {
t.Fatalf("Failed to decode response: %v", err)
}

Expand Down Expand Up @@ -680,17 +680,17 @@ func TestSSEServer(t *testing.T) {
}
defer resp.Body.Close()

endpointEvent, err = readSeeEvent(sseResp)
endpointEvent, err = readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}

respFromSee = strings.TrimSpace(
respFromSSE = strings.TrimSpace(
strings.Split(strings.Split(endpointEvent, "data: ")[1], "\n")[0],
)

response = make(map[string]interface{})
if err := json.NewDecoder(strings.NewReader(respFromSee)).Decode(&response); err != nil {
if err := json.NewDecoder(strings.NewReader(respFromSSE)).Decode(&response); err != nil {
t.Fatalf("Failed to decode response: %v", err)
}

Expand Down Expand Up @@ -1140,7 +1140,7 @@ func TestSSEServer(t *testing.T) {
registeredSession = s
}
})

mcpServer := NewMCPServer("test", "1.0.0", WithHooks(hooks))
testServer := NewTestServer(mcpServer)
defer testServer.Close()
Expand All @@ -1153,7 +1153,7 @@ func TestSSEServer(t *testing.T) {
defer sseResp.Body.Close()

// Read the endpoint event to ensure session is established
_, err = readSeeEvent(sseResp)
_, err = readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
Expand Down Expand Up @@ -1240,9 +1240,87 @@ func TestSSEServer(t *testing.T) {
t.Error("Expected final_tool to exist")
}
})

t.Run("TestServerResponseMarshalError", func(t *testing.T) {
mcpServer := NewMCPServer("test", "1.0.0",
WithResourceCapabilities(true, true),
WithHooks(&Hooks{
OnAfterInitialize: []OnAfterInitializeFunc{
func(ctx context.Context, id any, message *mcp.InitializeRequest, result *mcp.InitializeResult) {
result.Result.Meta = map[string]interface{}{"invalid": func() {}} // marshal will fail
},
},
}),
)
testServer := NewTestServer(mcpServer)
defer testServer.Close()

// Connect to SSE endpoint
sseResp, err := http.Get(fmt.Sprintf("%s/sse", testServer.URL))
if err != nil {
t.Fatalf("Failed to connect to SSE endpoint: %v", err)
}
defer sseResp.Body.Close()

// Read the endpoint event
endpointEvent, err := readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}
if !strings.Contains(endpointEvent, "event: endpoint") {
t.Fatalf("Expected endpoint event, got: %s", endpointEvent)
}

// Extract message endpoint URL
messageURL := strings.TrimSpace(
strings.Split(strings.Split(endpointEvent, "data: ")[1], "\n")[0],
)

// Send initialize request
initRequest := map[string]interface{}{
"jsonrpc": "2.0",
"id": 1,
"method": "initialize",
"params": map[string]interface{}{
"protocolVersion": "2024-11-05",
"clientInfo": map[string]interface{}{
"name": "test-client",
"version": "1.0.0",
},
},
}

requestBody, err := json.Marshal(initRequest)
if err != nil {
t.Fatalf("Failed to marshal request: %v", err)
}

resp, err := http.Post(
messageURL,
"application/json",
bytes.NewBuffer(requestBody),
)
if err != nil {
t.Fatalf("Failed to send message: %v", err)
}
defer resp.Body.Close()

if resp.StatusCode != http.StatusAccepted {
t.Errorf("Expected status 202, got %d", resp.StatusCode)
}

endpointEvent, err = readSSEEvent(sseResp)
if err != nil {
t.Fatalf("Failed to read SSE response: %v", err)
}

if !strings.Contains(endpointEvent, "\"id\": null") {
t.Errorf("Expected id to be null")
}
})
}

func readSeeEvent(sseResp *http.Response) (string, error) {
func readSSEEvent(sseResp *http.Response) (string, error) {
buf := make([]byte, 1024)
n, err := sseResp.Body.Read(buf)
if err != nil {
Expand Down