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mcp: fix broken client root capabilities (#698)

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To address #607, add ClientCapabilities.RootsV2, and populate it when
constructing sending and receiving InitializeParams.

Fixes #607
This commit is contained in:
Robert Findley 2025-12-11 10:16:56 -05:00 • committed by GitHub
commit a5e369ed12
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1 changed files with 288 additions and 57 deletions
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21
mcp/server.go
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@ -1138,7 +1138,7 @@ func (s *Server) AddReceivingMiddleware(middleware ...Middleware) {
// curating these method flags.
var serverMethodInfos = map[string]methodInfo{
methodComplete: newServerMethodInfo(serverMethod((*Server).complete), 0),
methodInitialize: newServerMethodInfo(serverSessionMethod((*ServerSession).initialize), 0),
methodInitialize: initializeMethodInfo(),
methodPing: newServerMethodInfo(serverSessionMethod((*ServerSession).ping), missingParamsOK),
methodListPrompts: newServerMethodInfo(serverMethod((*Server).listPrompts), missingParamsOK),
methodGetPrompt: newServerMethodInfo(serverMethod((*Server).getPrompt), 0),
@ -1156,6 +1156,25 @@ var serverMethodInfos = map[string]methodInfo{
notificationProgress: newServerMethodInfo(serverSessionMethod((*ServerSession).callProgressNotificationHandler), notification),
}
// initializeMethodInfo handles the workaround for #607: we must set
// params.Capabilities.RootsV2.
func initializeMethodInfo() methodInfo {
info := newServerMethodInfo(serverSessionMethod((*ServerSession).initialize), 0)
info.unmarshalParams = func(m json.RawMessage) (Params, error) {
var params *initializeParamsV2
if m != nil {
if err := json.Unmarshal(m, &params); err != nil {
return nil, fmt.Errorf("unmarshaling %q into a %T: %w", m, params, err)
}
}
if params == nil {
return nil, fmt.Errorf(`missing required "params"`)
}
return params.toV1(), nil
}
return info
}
func (ss *ServerSession) sendingMethodInfos() map[string]methodInfo { return clientMethodInfos }
func (ss *ServerSession) receivingMethodInfos() map[string]methodInfo { return serverMethodInfos }