Address review comments

cmake/GoogleCloudCppFeatures.cmake

@@ -401,9 +401,6 @@ function (google_cloud_cpp_enable_features)
             if (NOT ("storage" IN_LIST GOOGLE_CLOUD_CPP_ENABLE))
                 add_subdirectory(google/cloud/storage)
             endif ()
-        elseif ("${feature}" STREQUAL "storage")
-            add_subdirectory(protos/google/cloud/storage/tests)
-            add_subdirectory(google/cloud/storage)
         elseif ("${feature}" STREQUAL "experimental-bigquery_rest")
             if (NOT ("bigquery" IN_LIST GOOGLE_CLOUD_CPP_ENABLE))
                 add_subdirectory(google/cloud/bigquery)
@@ -431,6 +428,13 @@ function (google_cloud_cpp_enable_features)
                 )
                 continue()
             endif ()
+            if (IS_DIRECTORY
+                "${PROJECT_SOURCE_DIR}/protos/google/cloud/${feature}"
+                AND EXISTS
+                    "${PROJECT_SOURCE_DIR}/protos/google/cloud/${feature}/CMakeLists.txt"
+            )
+                add_subdirectory(protos/google/cloud/${feature})
+            endif ()
             add_subdirectory(google/cloud/${feature})
             if (GOOGLE_CLOUD_CPP_ENABLE_EXAMPLES
                 AND IS_DIRECTORY

protos/google/cloud/storage/CMakeLists.txt

@@ -0,0 +1,15 @@
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+add_subdirectory(tests)