address some review comments

ci/cloudbuild/builds/cmake-install.sh

@@ -110,7 +110,6 @@ expected_dirs+=(
   ./lib64/cmake/google_cloud_cpp_googleapis
   ./lib64/cmake/google_cloud_cpp_grafeas
   ./lib64/cmake/google_cloud_cpp_grpc_utils
-  ./lib64/cmake/google_cloud_cpp_pubsub
   ./lib64/cmake/google_cloud_cpp_pubsub_mocks
   ./lib64/cmake/google_cloud_cpp_rest_internal
   ./lib64/cmake/google_cloud_cpp_rest_protobuf_internal

ci/verify_current_targets/CMakeLists.txt

@@ -30,6 +30,7 @@ set(ga_libraries
     iam
     logging
     pubsub
+    pubsub_mocks
     spanner
     storage)
 

cmake/AddPkgConfig.cmake

@@ -35,16 +35,16 @@ macro (google_cloud_cpp_set_pkgconfig_paths)
 endmacro ()
 
 #
-# Create the pkgconfig configuration file (aka *.pc file) and the rules to
-# install it.
+# Implementation to create the pkgconfig configuration file (aka *.pc file) and
+# the rules to install it.
 #
 # * library: the name of the library, such as `storage`, or `spanner`
 # * ARGN: the names of any pkgconfig modules the generated module depends on
 #
-function (google_cloud_cpp_add_pkgconfig library name description)
+function (google_cloud_cpp_add_pkgconfig_impl library name description pc_libs)
     set(GOOGLE_CLOUD_CPP_PC_NAME "${name}")
     set(GOOGLE_CLOUD_CPP_PC_DESCRIPTION "${description}")
-    set(GOOGLE_CLOUD_CPP_PC_LIBS "-lgoogle_cloud_cpp_${library}")
+    set(GOOGLE_CLOUD_CPP_PC_LIBS "${pc_libs}")
     string(CONCAT GOOGLE_CLOUD_CPP_PC_REQUIRES ${ARGN})
     google_cloud_cpp_set_pkgconfig_paths()
 
@@ -56,3 +56,28 @@ function (google_cloud_cpp_add_pkgconfig library name description)
         DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig"
         COMPONENT google_cloud_cpp_development)
 endfunction ()
+
+#
+# Create the pkgconfig configuration file (aka *.pc file) and the rules to
+# install it.
+#
+# * library: the name of the library, such as `storage`, or `spanner`
+# * ARGN: the names of any pkgconfig modules the generated module depends on
+#
+function (google_cloud_cpp_add_pkgconfig library name description)
+    google_cloud_cpp_add_pkgconfig_impl("${library}" "${name}" "${description}"
+                                        "-lgoogle_cloud_cpp_${library}" ${ARGN})
+endfunction ()
+
+#
+# Create the pkgconfig configuration file (aka *.pc file) and the rules to
+# install it for an interface library. These libraries only contain headers, so
+# they do not generate lib files to link against with `-l`.
+#
+# * library: the name of the library, such as `storage`, or `spanner`
+# * ARGN: the names of any pkgconfig modules the generated module depends on
+#
+function (google_cloud_cpp_add_pkgconfig_interface library name description)
+    google_cloud_cpp_add_pkgconfig_impl("${library}" "${name}" "${description}"
+                                        "" ${ARGN})
+endfunction ()

google/cloud/pubsub/CMakeLists.txt

@@ -426,14 +426,13 @@ install(
     DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/google_cloud_cpp_pubsub"
     COMPONENT google_cloud_cpp_development)
 
-google_cloud_cpp_add_pkgconfig(
-    pubsub_mocks "Mocks for the Google Cloud Pub/Sub C++ Client Library"
-    "Provides mock classes for the Google Cloud Pub/Sub C++ APIs."
-    "google_cloud_cpp_pubsub" " gtest")
+google_cloud_cpp_add_pkgconfig_interface(
+    pubsub_mocks "Google Cloud C++ Pub/Sub Mocks"
+    "Mocks for the Google Cloud Pub/Sub C++ Client Library"
+    "google_cloud_cpp_pubsub" " gmock_main")
 
 # Create and install the CMake configuration files.
-include(CMakePackageConfigHelpers)
-configure_file("config-mocks.cmake.in"
+configure_file("mocks-config.cmake.in"
                "google_cloud_cpp_pubsub_mocks-config.cmake" @ONLY)
 write_basic_package_version_file(
     "google_cloud_cpp_pubsub_mocks-config-version.cmake"

google/cloud/pubsub/config-mocks.cmake.in → google/cloud/pubsub/mocks-config.cmake.in

@@ -1,4 +1,4 @@
-# Copyright 2020 Google LLC
+# Copyright 2022 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,6 +14,6 @@
 
 include(CMakeFindDependencyMacro)
 find_dependency(google_cloud_cpp_pubsub)
-find_dependency(gtest)
+find_dependency(GTest)
 
 include("${CMAKE_CURRENT_LIST_DIR}/pubsub_mocks-targets.cmake")