fix(server): support unique method lookup when service name lookup fails (cloudwego#1873)

Author: jayantxie

server/service.go

@@ -276,13 +276,8 @@ func (s *services) SearchService(svcName, methodName string, strict bool, codecT
 			if svc := s.knownSvcMap[svcName]; svc != nil {
 				return svc.svcInfo
 			}
-			if svcName == serviceinfo.GenericService || svcName == serviceinfo.CombineServiceName {
-				// Maybe combine or generic service name,
-				// because Kitex client will write these two service name if the version is between v0.9.0-v0.9.1
-				// TODO: remove this logic if this version range is converged
-				if svcInfo := s.searchByMethodName(methodName); svcInfo != nil {
-					return svcInfo
-				}
+			if svcInfo := s.searchUniqueByMethodName(methodName); svcInfo != nil {
+				return svcInfo
 			}
 		}
 	}
@@ -292,6 +287,28 @@ func (s *services) SearchService(svcName, methodName string, strict bool, codecT
 	return nil
 }
 
+// SearchUniqueByMethodName searches for a unique service by method name.
+// It returns nil if there are multiple services with the same method name.
+func (s *services) searchUniqueByMethodName(methodName string) (unique *serviceinfo.ServiceInfo) {
+	if s.fallbackSvc != nil {
+		// check whether fallback service has the method
+		if mi := s.fallbackSvc.svcInfo.MethodInfo(notAllowBinaryGenericCtx, methodName); mi != nil {
+			unique = s.fallbackSvc.svcInfo
+		}
+	}
+	// match other services
+	for _, svc := range s.nonFallbackSvcs {
+		if mi := svc.svcInfo.MethodInfo(notAllowBinaryGenericCtx, methodName); mi != nil {
+			if unique == nil {
+				unique = svc.svcInfo
+			} else {
+				return nil
+			}
+		}
+	}
+	return unique
+}
+
 // getTargetSvcInfo returns the service info if there is only one service registered.
 func (s *services) getTargetSvcInfo() *serviceinfo.ServiceInfo {
 	if len(s.knownSvcMap) != 1 {

server/service_test.go

@@ -156,7 +156,7 @@ func TestSearchService(t *testing.T) {
 			},
 			serviceName:   serviceinfo.GenericService,
 			methodName:    mocks.MockMethod,
-			expectSvcInfo: mocks.ServiceInfo(),
+			expectSvcInfo: nil,
 		},
 		{
 			svcs: []svc{
@@ -170,7 +170,7 @@ func TestSearchService(t *testing.T) {
 			},
 			serviceName:   "xxxxxx",
 			methodName:    mocks.MockExceptionMethod,
-			expectSvcInfo: nil,
+			expectSvcInfo: mocks.ServiceInfo(),
 		},
 		{
 			svcs: []svc{