fix(telemetry): sync.Once for identity stitch, rename constant, add tests

- Wrap StitchLogin callback in sync.Once to prevent duplicate $alias
  calls if concurrent API responses both carry X-Gotrue-Id
- Rename HeaderGotrueId → HeaderGotrueID per Go naming conventions
- Add tests for nil callback and inner transport error paths

Author: seanoliver

cmd/root.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/signal"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/getsentry/sentry-go"
@@ -141,11 +142,14 @@ var (
 				ctx = telemetry.WithService(ctx, service)
 			}
 			if service != nil {
+				var stitchOnce sync.Once
 				utils.OnGotrueID = func(gotrueID string) {
 					if service.NeedsIdentityStitch() {
-						if err := service.StitchLogin(gotrueID); err != nil {
-							fmt.Fprintln(utils.GetDebugLogger(), err)
-						}
+						stitchOnce.Do(func() {
+							if err := service.StitchLogin(gotrueID); err != nil {
+								fmt.Fprintln(utils.GetDebugLogger(), err)
+							}
+						})
 					}
 				}
 			}

internal/utils/identity_transport.go

@@ -2,7 +2,7 @@ package utils
 
 import "net/http"
 
-const HeaderGotrueId = "X-Gotrue-Id"
+const HeaderGotrueID = "X-Gotrue-Id"
 
 type identityTransport struct {
 	http.RoundTripper
@@ -14,7 +14,7 @@ func (t *identityTransport) RoundTrip(req *http.Request) (*http.Response, error)
 	if err != nil {
 		return resp, err
 	}
-	if id := resp.Header.Get(HeaderGotrueId); id != "" && t.onGotrueID != nil {
+	if id := resp.Header.Get(HeaderGotrueID); id != "" && t.onGotrueID != nil {
 		t.onGotrueID(id)
 	}
 	return resp, err

internal/utils/identity_transport_test.go

@@ -42,6 +42,37 @@ func TestIdentityTransport_IgnoresWhenHeaderMissing(t *testing.T) {
 	assert.Empty(t, captured)
 }
 
+func TestIdentityTransport_NilCallbackDoesNotPanic(t *testing.T) {
+	transport := &identityTransport{
+		RoundTripper: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+			return &http.Response{
+				StatusCode: 200,
+				Header:     http.Header{"X-Gotrue-Id": []string{"user-abc-123"}},
+			}, nil
+		}),
+		onGotrueID: nil,
+	}
+	req, _ := http.NewRequest("GET", "https://api.supabase.io/v1/projects", nil)
+	resp, err := transport.RoundTrip(req)
+	assert.NoError(t, err)
+	assert.Equal(t, 200, resp.StatusCode)
+}
+
+func TestIdentityTransport_InnerTransportError(t *testing.T) {
+	var captured string
+	transport := &identityTransport{
+		RoundTripper: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+			return nil, assert.AnError
+		}),
+		onGotrueID: func(id string) { captured = id },
+	}
+	req, _ := http.NewRequest("GET", "https://api.supabase.io/v1/projects", nil)
+	resp, err := transport.RoundTrip(req)
+	assert.Error(t, err)
+	assert.Nil(t, resp)
+	assert.Empty(t, captured)
+}
+
 // roundTripFunc is a test helper to create inline RoundTrippers.
 type roundTripFunc func(*http.Request) (*http.Response, error)