fix(auth): match SQLite username constraint errors (#3295)

- Match the UNIQUE constraint text anywhere in the SQLite error message.
- Add regression tests for the SSO auto-registration username retry.
- Verify the fix with targeted SSO tests and go vet.

Co-authored-by: LunelleEverdawn <lunelle+suyunmeng@oplist.org>

server/handles/ssologin.go

@@ -296,7 +296,7 @@ func autoRegister(username, userID string, err error) (*model.User, error) {
 		SsoID:      userID,
 	}
 	if err = db.CreateUser(user); err != nil {
-		if strings.HasPrefix(err.Error(), "UNIQUE constraint failed") && strings.HasSuffix(err.Error(), "username") {
+		if strings.Contains(err.Error(), "UNIQUE constraint failed") && strings.Contains(err.Error(), "username") {
 			user.Username = user.Username + "_" + userID
 			if err = db.CreateUser(user); err != nil {
 				return nil, err

server/handles/ssologin_register_test.go

@@ -0,0 +1,58 @@
+package handles
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/OpenListTeam/OpenList/v4/internal/conf"
+	"github.com/OpenListTeam/OpenList/v4/internal/db"
+	"github.com/OpenListTeam/OpenList/v4/internal/model"
+	"github.com/OpenListTeam/OpenList/v4/internal/op"
+	"github.com/glebarez/sqlite"
+	"gorm.io/gorm"
+)
+
+func setupAutoRegisterTest(t *testing.T) {
+	t.Helper()
+	database, err := gorm.Open(sqlite.Open("file:"+t.Name()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	conf.Conf = conf.DefaultConfig(t.TempDir())
+	db.Init(database)
+	for key, value := range map[string]string{
+		conf.SSOAutoRegister:      "true",
+		conf.SSODefaultPermission: "0",
+		conf.SSODefaultDir:        "/",
+	} {
+		op.Cache.SetSetting(key, &model.SettingItem{Key: key, Value: value})
+	}
+	t.Cleanup(op.Cache.ClearAll)
+}
+
+// Re-login after unbinding SSO: the username is still taken by the unbound
+// user, so registration must retry with the SSO ID suffix instead of failing.
+func TestAutoRegisterRetriesOnUsernameConflict(t *testing.T) {
+	setupAutoRegisterTest(t)
+	if err := db.CreateUser(&model.User{Username: "alice"}); err != nil {
+		t.Fatal(err)
+	}
+
+	user, err := autoRegister("alice", "sso-1", gorm.ErrRecordNotFound)
+	if err != nil {
+		t.Fatalf("expected retry to succeed, got: %v", err)
+	}
+	if user.Username != "alice_sso-1" || user.SsoID != "sso-1" {
+		t.Fatalf("unexpected user: username=%q sso_id=%q", user.Username, user.SsoID)
+	}
+}
+
+func TestAutoRegisterReturnsUnrelatedErrors(t *testing.T) {
+	setupAutoRegisterTest(t)
+	want := errors.New("unrelated")
+
+	user, err := autoRegister("alice", "sso-1", want)
+	if user != nil || !errors.Is(err, want) {
+		t.Fatalf("expected original error, got user=%v err=%v", user, err)
+	}
+}