cleanup(cmake): re-support transition libraries (#12753)

dbolduc · web-flow · commit e3c2d5907ea5 · 2023-09-28T22:26:37.000-04:00
diff --git a/cmake/GoogleCloudCppLibrary.cmake b/cmake/GoogleCloudCppLibrary.cmake
@@ -153,16 +153,24 @@ endfunction ()
 function (google_cloud_cpp_add_ga_grpc_library library display_name)
     cmake_parse_arguments(
         _opt
-        "EXPERIMENTAL"
+        "EXPERIMENTAL;TRANSITION"
         ""
         "ADDITIONAL_PROTO_LISTS;BACKWARDS_COMPAT_PROTO_TARGETS;CROSS_LIB_DEPS;SHARED_PROTO_DEPS"
         ${ARGN})
+    if (_opt_EXPERIMENTAL AND _opt_TRANSITION)
+        message(
+            FATAL_ERROR
+                "EXPERIMENTAL and TRANSITION keywords are mutually exclusive. Only supply one."
+        )
+    endif ()
+
     set(library_target "google_cloud_cpp_${library}")
     set(mocks_target "google_cloud_cpp_${library}_mocks")
     set(protos_target "google_cloud_cpp_${library}_protos")
     set(library_alias "google-cloud-cpp::${library}")
+    set(experimental_alias "google-cloud-cpp::experimental-${library}")
     if (_opt_EXPERIMENTAL)
-        set(library_alias "google-cloud-cpp::experimental-${library}")
+        set(library_alias "${experimental_alias}")
     endif ()
 
     include(GoogleapisConfig)
@@ -323,6 +331,14 @@ function (google_cloud_cpp_add_ga_grpc_library library display_name)
     endforeach ()
     string(JOIN "\n" GOOGLE_CLOUD_CPP_ADDITIONAL_FIND_DEPENDENCIES
            ${find_dependencies})
+    if (_opt_TRANSITION)
+        set(cmake_config_transition_lines
+            "if (NOT TARGET ${experimental_alias})"
+            "    add_library(${experimental_alias} ALIAS ${library_alias})"
+            "endif ()")
+        string(JOIN "\n" GOOGLE_CLOUD_CPP_CONFIG_TRANSITION_TARGETS
+               ${cmake_config_transition_lines})
+    endif ()
     configure_file("${PROJECT_SOURCE_DIR}/cmake/templates/config.cmake.in"
                    "${library_target}-config.cmake" @ONLY)
     write_basic_package_version_file(
diff --git a/cmake/templates/config.cmake.in b/cmake/templates/config.cmake.in
@@ -21,3 +21,5 @@ find_dependency(absl)
 @GOOGLE_CLOUD_CPP_ADDITIONAL_FIND_DEPENDENCIES@
 
 include("${CMAKE_CURRENT_LIST_DIR}/@GOOGLE_CLOUD_CPP_CONFIG_LIBRARY@-targets.cmake")
+
+@GOOGLE_CLOUD_CPP_CONFIG_TRANSITION_TARGETS@
diff --git a/doc/contributor/howto-guide-declare-a-library-ga.md b/doc/contributor/howto-guide-declare-a-library-ga.md
@@ -86,21 +86,10 @@ for lib in "${ga[@]}"; do sed -i 's/^Please note that the Google Cloud C/While t
 
 ### `google/cloud/${library}/CMakeLists.txt`:
 
-Remove the EXPERIMENTAL keyword from the library definition.
+Update the CMake library targets.
 
 ```shell
-for lib in "${ga[@]}"; do sed -i 's/EXPERIMENTAL//' google/cloud/${lib}/CMakeLists.txt; done
-```
-
-### `google/cloud/${library}/config.cmake.in`:
-
-Add an alias to help transition from `google-cloud-cpp::experimental-${library}`
-to `google-cloud-cpp::${library}`:
-
-```shell
-for lib in "${ga[@]}"; do
-  printf "\nif (NOT TARGET google-cloud-cpp::experimental-%s)\n    add_library(google-cloud-cpp::experimental-%s ALIAS google-cloud-cpp::%s)\nendif ()\n" "${lib}" "${lib}" "${lib}" >>google/cloud/${lib}/config.cmake.in
-done
+for lib in "${ga[@]}"; do sed -i 's/EXPERIMENTAL/TRANSITION/' google/cloud/${lib}/CMakeLists.txt; done
 ```
 
 ## Reference the GA targets in the quickstarts
@@ -128,5 +117,5 @@ In the following release, move the libraries from
 Then remove the CMake aliases.
 
 ```shell
-for lib in "${ga[@]}"; do sed -i '1,/-targets.cmake")/!d' google/cloud/${lib}/config.cmake.in; done
+for lib in "${ga[@]}"; do sed -i 's/TRANSITION//' google/cloud/${lib}/CMakeLists.txt; done
 ```
