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mcp: establish the streamable client standalone SSE stream in Connect (#604)

Browse source 
When Connect returns, client should be guaranteed that the streamable
SSE stream is connected.

Fixes #583
This commit is contained in:
Robert Findley 2025-10-27 14:03:22 -04:00 • committed by GitHub
commit ae6bda692b
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GPG key ID: B5690EEEBB952194
1 changed files with 118 additions and 159 deletions
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78
mcp/streamable_client_test.go
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@ -13,7 +13,6 @@ import (
"strings"
"sync"
"testing"
"time"
"github.com/google/go-cmp/cmp"
"github.com/modelcontextprotocol/go-sdk/internal/jsonrpc2"
@ -156,7 +155,6 @@ func TestStreamableClientTransportLifecycle(t *testing.T) {
header: header{
"Content-Type": "text/event-stream",
},
optional: true,
wantProtocolVersion: latestProtocolVersion,
},
{"DELETE", "123", ""}: {},
@ -205,8 +203,7 @@ func TestStreamableClientRedundantDelete(t *testing.T) {
wantProtocolVersion: latestProtocolVersion,
},
{"GET", "123", ""}: {
status: http.StatusMethodNotAllowed,
optional: true,
status: http.StatusMethodNotAllowed,
},
{"POST", "123", methodListTools}: {
status: http.StatusNotFound,
@ -268,14 +265,6 @@ func TestStreamableClientGETHandling(t *testing.T) {
status: test.status,
wantProtocolVersion: latestProtocolVersion,
},
{"POST", "123", methodListTools}: {
header: header{
"Content-Type": "application/json",
sessionIDHeader: "123",
},
body: jsonBody(t, resp(2, &ListToolsResult{Tools: []*Tool{}}, nil)),
optional: true,
},
{"DELETE", "123", ""}: {optional: true},
},
}
@ -285,36 +274,18 @@ func TestStreamableClientGETHandling(t *testing.T) {
transport := &StreamableClientTransport{Endpoint: httpServer.URL}
client := NewClient(testImpl, nil)
session, err := client.Connect(ctx, transport, nil)
if err != nil {
t.Fatalf("client.Connect() failed: %v", err)
if err == nil {
defer session.Close()
}
// Since we need the client to observe the result of the hanging GET,
// wait for all requests to be handled.
start := time.Now()
delay := 1 * time.Millisecond
for range 10 {
if len(fake.missingRequests()) == 0 {
break
if test.wantErrorContaining != "" {
if err == nil {
t.Fatalf("Connect succeeded unexpectedly, want error containing %q", test.wantErrorContaining)
}
if got := err.Error(); !strings.Contains(got, test.wantErrorContaining) {
t.Errorf("Connect error = %q, want containing %q", got, test.wantErrorContaining)
}
time.Sleep(delay)
delay *= 2
}
if missing := fake.missingRequests(); len(missing) > 0 {
t.Errorf("did not receive expected requests after %s: %v", time.Since(start), missing)
}
_, err = session.ListTools(ctx, nil)
if (err != nil) != (test.wantErrorContaining != "") {
t.Errorf("After initialization, got error %v, want containing %q", err, test.wantErrorContaining)
} else if err != nil {
if !strings.Contains(err.Error(), test.wantErrorContaining) {
t.Errorf("After initialization, got error %s, want containing %q", err, test.wantErrorContaining)
}
}
if err := session.Close(); err != nil {
t.Errorf("closing session: %v", err)
t.Fatalf("Connect failed: %v", err)
}
})
}
@ -329,13 +300,12 @@ func TestStreamableClientStrictness(t *testing.T) {
initializedStatus int
getStatus int
wantConnectError bool
wantListError bool
}{
{"conformant server", true, http.StatusAccepted, http.StatusMethodNotAllowed, false, false},
{"strict initialized", true, http.StatusOK, http.StatusMethodNotAllowed, true, false},
{"unstrict initialized", false, http.StatusOK, http.StatusMethodNotAllowed, false, false},
{"strict GET", true, http.StatusAccepted, http.StatusNotFound, false, true},
{"unstrict GET", false, http.StatusOK, http.StatusNotFound, false, false},
{"conformant server", true, http.StatusAccepted, http.StatusMethodNotAllowed, false},
{"strict initialized", true, http.StatusOK, http.StatusMethodNotAllowed, true},
{"unstrict initialized", false, http.StatusOK, http.StatusMethodNotAllowed, false},
{"strict GET", true, http.StatusAccepted, http.StatusNotFound, true},
{"unstrict GET", false, http.StatusOK, http.StatusNotFound, false},
}
for _, test := range tests {
t.Run(test.label, func(t *testing.T) {
@ -383,23 +353,9 @@ func TestStreamableClientStrictness(t *testing.T) {
if err != nil {
return
}
// Since we need the client to observe the result of the hanging GET,
// wait for all requests to be handled.
start := time.Now()
delay := 1 * time.Millisecond
for range 10 {
if len(fake.missingRequests()) == 0 {
break
}
time.Sleep(delay)
delay *= 2
}
if missing := fake.missingRequests(); len(missing) > 0 {
t.Errorf("did not receive expected requests after %s: %v", time.Since(start), missing)
}
_, err = session.ListTools(ctx, nil)
if (err != nil) != test.wantListError {
t.Errorf("ListTools returned error %v; want error: %t", err, test.wantListError)
if err != nil {
t.Errorf("ListTools failed: %v", err)
}
if err := session.Close(); err != nil {
t.Errorf("closing session: %v", err)