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internal/mcp: meta and progress token

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Meta is a struct that contains a map[string]any, and a ProgressToken
field.

Each Params and Result type has a Meta as a value field.

Meta marshals and unmarshals specially, so the ProgressToken field
becomes part of the map. The marshalling code is generalized in
anticipation of every Params and Result growing a map of additional
properties.

Change-Id: I6d2f34270d33501c96437f24f91ef3e51d20d955
Reviewed-on: https://go-review.googlesource.com/c/tools/+/674956
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Jonathan Amsterdam 2025-05-21 07:11:50 -04:00 • committed by Gopher Robot
commit 7130f0f081
1 changed files with 548 additions and 115 deletions
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22
mcp/client.go
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@ -162,7 +162,7 @@ func (c *Client) RemoveRoots(uris ...string) {
// changeAndNotify is called when a feature is added or removed.
// It calls change, which should do the work and report whether a change actually occurred.
// If there was a change, it notifies a snapshot of the sessions.
func (c *Client) changeAndNotify(notification string, params any, change func() bool) {
func (c *Client) changeAndNotify(notification string, params Params, change func() bool) {
var sessions []*ClientSession
// Lock for the change, but not for the notification.
c.mu.Lock()
@ -231,8 +231,8 @@ func (cs *ClientSession) methodHandler() MethodHandler[ClientSession] {
// getConn implements [session.getConn].
func (cs *ClientSession) getConn() *jsonrpc2.Connection { return cs.conn }
func (c *ClientSession) ping(ct context.Context, params *PingParams) (struct{}, error) {
return struct{}{}, nil
func (c *ClientSession) ping(ct context.Context, params *PingParams) (Result, error) {
return emptyResult{}, nil
}
// Ping makes an MCP "ping" request to the server.
@ -296,29 +296,21 @@ func (c *ClientSession) ReadResource(ctx context.Context, params *ReadResourcePa
return standardCall[ReadResourceResult](ctx, c.conn, methodReadResource, params)
}
func (c *Client) callToolChangedHandler(ctx context.Context, s *ClientSession, params *ToolListChangedParams) (any, error) {
func (c *Client) callToolChangedHandler(ctx context.Context, s *ClientSession, params *ToolListChangedParams) (Result, error) {
return callNotificationHandler(ctx, c.opts.ToolListChangedHandler, s, params)
}
func (c *Client) callPromptChangedHandler(ctx context.Context, s *ClientSession, params *PromptListChangedParams) (any, error) {
func (c *Client) callPromptChangedHandler(ctx context.Context, s *ClientSession, params *PromptListChangedParams) (Result, error) {
return callNotificationHandler(ctx, c.opts.PromptListChangedHandler, s, params)
}
func (c *Client) callResourceChangedHandler(ctx context.Context, s *ClientSession, params *ResourceListChangedParams) (any, error) {
func (c *Client) callResourceChangedHandler(ctx context.Context, s *ClientSession, params *ResourceListChangedParams) (Result, error) {
return callNotificationHandler(ctx, c.opts.ResourceListChangedHandler, s, params)
}
func (c *Client) callLoggingHandler(ctx context.Context, cs *ClientSession, params *LoggingMessageParams) (any, error) {
func (c *Client) callLoggingHandler(ctx context.Context, cs *ClientSession, params *LoggingMessageParams) (Result, error) {
if h := c.opts.LoggingMessageHandler; h != nil {
h(ctx, cs, params)
}
return nil, nil
}
func standardCall[TRes, TParams any](ctx context.Context, conn *jsonrpc2.Connection, method string, params TParams) (*TRes, error) {
var result TRes
if err := call(ctx, conn, method, params, &result); err != nil {
return nil, err
}
return &result, nil
}