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mcp: handle missing params #209

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20 changes: 10 additions & 10 deletions mcp/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -287,16 +287,16 @@ func (c *Client) AddReceivingMiddleware(middleware ...Middleware[*ClientSession]

// clientMethodInfos maps from the RPC method name to serverMethodInfos.
var clientMethodInfos = map[string]methodInfo{
methodComplete: newMethodInfo(sessionMethod((*ClientSession).Complete), true),
methodPing: newMethodInfo(sessionMethod((*ClientSession).ping), true),
methodListRoots: newMethodInfo(clientMethod((*Client).listRoots), true),
methodCreateMessage: newMethodInfo(clientMethod((*Client).createMessage), true),
notificationToolListChanged: newMethodInfo(clientMethod((*Client).callToolChangedHandler), false),
notificationPromptListChanged: newMethodInfo(clientMethod((*Client).callPromptChangedHandler), false),
notificationResourceListChanged: newMethodInfo(clientMethod((*Client).callResourceChangedHandler), false),
notificationResourceUpdated: newMethodInfo(clientMethod((*Client).callResourceUpdatedHandler), false),
notificationLoggingMessage: newMethodInfo(clientMethod((*Client).callLoggingHandler), false),
notificationProgress: newMethodInfo(sessionMethod((*ClientSession).callProgressNotificationHandler), false),
methodComplete: newMethodInfo(sessionMethod((*ClientSession).Complete), true, nil),
methodPing: newMethodInfo(sessionMethod((*ClientSession).ping), true, nil),
methodListRoots: newMethodInfo(clientMethod((*Client).listRoots), true, nil),
methodCreateMessage: newMethodInfo(clientMethod((*Client).createMessage), true, nil),
notificationToolListChanged: newMethodInfo(clientMethod((*Client).callToolChangedHandler), false, nil),
notificationPromptListChanged: newMethodInfo(clientMethod((*Client).callPromptChangedHandler), false, nil),
notificationResourceListChanged: newMethodInfo(clientMethod((*Client).callResourceChangedHandler), false, nil),
notificationResourceUpdated: newMethodInfo(clientMethod((*Client).callResourceUpdatedHandler), false, nil),
notificationLoggingMessage: newMethodInfo(clientMethod((*Client).callLoggingHandler), false, nil),
notificationProgress: newMethodInfo(sessionMethod((*ClientSession).callProgressNotificationHandler), false, nil),
}

func (cs *ClientSession) sendingMethodInfos() map[string]methodInfo {
Expand Down
49 changes: 32 additions & 17 deletions mcp/server.go
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Expand Up @@ -22,6 +22,7 @@ import (
"github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2"
"github.com/modelcontextprotocol/go-sdk/internal/util"
"github.com/modelcontextprotocol/go-sdk/jsonrpc"
"github.com/modelcontextprotocol/go-sdk/jsonschema"
)

const DefaultPageSize = 1000
Expand Down Expand Up @@ -682,24 +683,38 @@ func (s *Server) AddReceivingMiddleware(middleware ...Middleware[*ServerSession]
addMiddleware(&s.receivingMethodHandler_, middleware)
}

func must[T any](t T, err error) T {
if err != nil {
panic(err)
}
return t
}

// serverMethodInfos maps from the RPC method name to serverMethodInfos.
var serverMethodInfos = map[string]methodInfo{
methodComplete: newMethodInfo(serverMethod((*Server).complete), true),
methodInitialize: newMethodInfo(sessionMethod((*ServerSession).initialize), true),
methodPing: newMethodInfo(sessionMethod((*ServerSession).ping), true),
methodListPrompts: newMethodInfo(serverMethod((*Server).listPrompts), true),
methodGetPrompt: newMethodInfo(serverMethod((*Server).getPrompt), true),
methodListTools: newMethodInfo(serverMethod((*Server).listTools), true),
methodCallTool: newMethodInfo(serverMethod((*Server).callTool), true),
methodListResources: newMethodInfo(serverMethod((*Server).listResources), true),
methodListResourceTemplates: newMethodInfo(serverMethod((*Server).listResourceTemplates), true),
methodReadResource: newMethodInfo(serverMethod((*Server).readResource), true),
methodSetLevel: newMethodInfo(sessionMethod((*ServerSession).setLevel), true),
methodSubscribe: newMethodInfo(serverMethod((*Server).subscribe), true),
methodUnsubscribe: newMethodInfo(serverMethod((*Server).unsubscribe), true),
notificationInitialized: newMethodInfo(serverMethod((*Server).callInitializedHandler), false),
notificationRootsListChanged: newMethodInfo(serverMethod((*Server).callRootsListChangedHandler), false),
notificationProgress: newMethodInfo(sessionMethod((*ServerSession).callProgressNotificationHandler), false),
var serverMethodInfos map[string]methodInfo

func init() {
initializeSchema := must(jsonschema.For[*InitializeParams]())
initializeSchema.Required = []string{"capabilities", "clientInfo", "protocolVersion"}

serverMethodInfos = map[string]methodInfo{
methodComplete: newMethodInfo(serverMethod((*Server).complete), true, nil),
methodInitialize: newMethodInfo(sessionMethod((*ServerSession).initialize), true, initializeSchema),
methodPing: newMethodInfo(sessionMethod((*ServerSession).ping), true, nil),
methodListPrompts: newMethodInfo(serverMethod((*Server).listPrompts), true, nil),
methodGetPrompt: newMethodInfo(serverMethod((*Server).getPrompt), true, nil),
methodListTools: newMethodInfo(serverMethod((*Server).listTools), true, nil),
methodCallTool: newMethodInfo(serverMethod((*Server).callTool), true, nil),
methodListResources: newMethodInfo(serverMethod((*Server).listResources), true, nil),
methodListResourceTemplates: newMethodInfo(serverMethod((*Server).listResourceTemplates), true, nil),
methodReadResource: newMethodInfo(serverMethod((*Server).readResource), true, nil),
methodSetLevel: newMethodInfo(sessionMethod((*ServerSession).setLevel), true, nil),
methodSubscribe: newMethodInfo(serverMethod((*Server).subscribe), true, nil),
methodUnsubscribe: newMethodInfo(serverMethod((*Server).unsubscribe), true, nil),
notificationInitialized: newMethodInfo(serverMethod((*Server).callInitializedHandler), false, nil),
notificationRootsListChanged: newMethodInfo(serverMethod((*Server).callRootsListChangedHandler), false, nil),
notificationProgress: newMethodInfo(sessionMethod((*ServerSession).callProgressNotificationHandler), false, nil),
}
}

func (ss *ServerSession) sendingMethodInfos() map[string]methodInfo { return clientMethodInfos }
Expand Down
20 changes: 18 additions & 2 deletions mcp/shared.go
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Expand Up @@ -21,6 +21,7 @@ import (

"github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2"
"github.com/modelcontextprotocol/go-sdk/jsonrpc"
"github.com/modelcontextprotocol/go-sdk/jsonschema"
)

// latestProtocolVersion is the latest protocol version that this version of the SDK supports.
Expand Down Expand Up @@ -197,14 +198,29 @@ type paramsPtr[T any] interface {
//
// If isRequest is set, the method is treated as a request rather than a
// notification.
func newMethodInfo[S Session, P paramsPtr[T], R Result, T any](d typedMethodHandler[S, P, R], isRequest bool) methodInfo {
func newMethodInfo[S Session, P paramsPtr[T], R Result, T any](d typedMethodHandler[S, P, R], isRequest bool, paramSchema *jsonschema.Schema) methodInfo {
var resolved *jsonschema.Resolved
if paramSchema != nil {
var err error
resolved, err = paramSchema.Resolve(nil)
if err != nil {
panic(err)
}
}
return methodInfo{
isRequest: isRequest,
unmarshalParams: func(m json.RawMessage) (Params, error) {
var p P
if m != nil {
if err := json.Unmarshal(m, &p); err != nil {
return nil, fmt.Errorf("unmarshaling %q into a %T: %w", m, p, err)
return nil, fmt.Errorf("unmarshaling params into a %T: %w", p, err)
}
} else if resolved != nil {
return nil, fmt.Errorf(`missing required "params"`)
}
if resolved != nil {
if err := resolved.Validate(p); err != nil {
return nil, fmt.Errorf("invalid params: %v", err)
}
}
return orZero[Params](p), nil
Expand Down
15 changes: 14 additions & 1 deletion mcp/testdata/conformance/server/bad_requests.txtar
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Expand Up @@ -4,10 +4,10 @@ bad requests.
Fixed bugs:
- No id in 'initialize' should not panic (#197).
- No id in 'ping' should not panic (#194).
- No params in 'initialize' should not panic (#195).
- Notifications with IDs should not be treated like requests.

TODO:
- No params in 'initialize' should not panic (#195).

-- prompts --
code_review
Expand All @@ -22,6 +22,11 @@ code_review
"clientInfo": { "name": "ExampleClient", "version": "1.0.0" }
}
}
{
"jsonrpc": "2.0",
"id": 1,
"method": "initialize"
}
{
"jsonrpc": "2.0",
"id": 2,
Expand All @@ -36,6 +41,14 @@ code_review
{"jsonrpc":"2.0", "method":"ping"}

-- server --
{
"jsonrpc": "2.0",
"id": 1,
"error": {
"code": 0,
"message": "handleRequest \"initialize\": missing required \"params\""
}
}
{
"jsonrpc": "2.0",
"id": 2,
Expand Down
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