FindGTest: Add target for gmock library

`googlemock` has been absorbed into the
[googletest](https://github.com/google/googletest) project and is built
and installed from the same source tree.

As GTest may be built with or without GMock, skip GMock if it is not
present.

Do not provide result variables for GMock.  They are not provided by
upstream GTest's CMake Package Configuration File.

Also update the test case to cover linking to `GTest::gmock`.

Help/release/dev/FindGTest-target-for-gmock.rst

@@ -0,0 +1,4 @@
+FindGTest-target-for-gmock
+--------------------------
+
+* The :module:`FindGTest` module now provides a target for GMock, if found.

Modules/FindGTest.cmake

@@ -22,6 +22,14 @@ Imported targets
 ``GTest::gtest_main``
   The Google Test ``gtest_main`` library, if found
 
+.. versionadded:: 3.23
+
+``GTest::gmock``
+  The Google Mock ``gmock`` library, if found; adds Thread::Thread
+  automatically
+``GTest::gmock_main``
+  The Google Mock ``gmock_main`` library, if found
+
 .. deprecated:: 3.20
   For backwards compatibility, this module defines additionally the
   following deprecated :prop_tgt:`IMPORTED` targets (available since 3.5):
@@ -32,7 +40,6 @@ Imported targets
 ``GTest::Main``
   The Google Test ``gtest_main`` library, if found
 
-
 Result variables
 ^^^^^^^^^^^^^^^^
 
@@ -245,15 +252,29 @@ if(MSVC AND GTEST_MSVC_SEARCH STREQUAL "MD")
     __gtest_find_library(GTEST_LIBRARY_DEBUG      gtest-mdd gtestd)
     __gtest_find_library(GTEST_MAIN_LIBRARY       gtest_main-md  gtest_main)
     __gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtest_main-mdd gtest_maind)
+    __gtest_find_library(GMOCK_LIBRARY            gmock-md  gmock)
+    __gtest_find_library(GMOCK_LIBRARY_DEBUG      gmock-mdd gmockd)
+    __gtest_find_library(GMOCK_MAIN_LIBRARY       gmock_main-md  gmock_main)
+    __gtest_find_library(GMOCK_MAIN_LIBRARY_DEBUG gmock_main-mdd gmock_maind)
 else()
     __gtest_find_library(GTEST_LIBRARY            gtest)
     __gtest_find_library(GTEST_LIBRARY_DEBUG      gtestd)
     __gtest_find_library(GTEST_MAIN_LIBRARY       gtest_main)
     __gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtest_maind)
+    __gtest_find_library(GMOCK_LIBRARY            gmock)
+    __gtest_find_library(GMOCK_LIBRARY_DEBUG      gmockd)
+    __gtest_find_library(GMOCK_MAIN_LIBRARY       gmock_main)
+    __gtest_find_library(GMOCK_MAIN_LIBRARY_DEBUG gmock_maind)
 endif()
 
 FIND_PACKAGE_HANDLE_STANDARD_ARGS(GTest DEFAULT_MSG GTEST_LIBRARY GTEST_INCLUDE_DIR GTEST_MAIN_LIBRARY)
 
+if(GMOCK_LIBRARY AND GMOCK_MAIN_LIBRARY)
+    set(GMock_FOUND True)
+else()
+    set(GMock_FOUND False)
+endif()
+
 if(GTest_FOUND)
     set(GTEST_INCLUDE_DIRS ${GTEST_INCLUDE_DIR})
     __gtest_append_debugs(GTEST_LIBRARIES      GTEST_LIBRARY)
@@ -292,3 +313,36 @@ if(GTest_FOUND)
 
     __gtest_define_backwards_compatible_library_targets()
 endif()
+
+if(GMock_FOUND)
+    if(NOT TARGET GTest::gmock)
+        __gtest_determine_library_type(GMOCK_LIBRARY)
+        add_library(GTest::gmock ${GMOCK_LIBRARY_TYPE} IMPORTED)
+        set(_gmock_link_libraries "GTest::gtest")
+        if(TARGET Threads::Threads)
+            list(APPEND _gmock_link_libraries Threads::Threads)
+        endif()
+        set_target_properties(GTest::gmock PROPERTIES
+            INTERFACE_LINK_LIBRARIES "${_gmock_link_libraries}")
+        if(GMOCK_LIBRARY_TYPE STREQUAL "SHARED")
+            set_target_properties(GTest::gmock PROPERTIES
+                INTERFACE_COMPILE_DEFINITIONS "GMOCK_LINKED_AS_SHARED_LIBRARY=1")
+        endif()
+        if(GTEST_INCLUDE_DIRS)
+            set_target_properties(GTest::gmock PROPERTIES
+                INTERFACE_INCLUDE_DIRECTORIES "${GTEST_INCLUDE_DIRS}")
+        endif()
+        __gtest_import_library(GTest::gmock GMOCK_LIBRARY "")
+        __gtest_import_library(GTest::gmock GMOCK_LIBRARY "RELEASE")
+        __gtest_import_library(GTest::gmock GMOCK_LIBRARY "DEBUG")
+    endif()
+    if(NOT TARGET GTest::gmock_main)
+        __gtest_determine_library_type(GMOCK_MAIN_LIBRARY)
+        add_library(GTest::gmock_main ${GMOCK_MAIN_LIBRARY_TYPE} IMPORTED)
+        set_target_properties(GTest::gmock_main PROPERTIES
+            INTERFACE_LINK_LIBRARIES "GTest::gmock")
+        __gtest_import_library(GTest::gmock_main GMOCK_MAIN_LIBRARY "")
+        __gtest_import_library(GTest::gmock_main GMOCK_MAIN_LIBRARY "RELEASE")
+        __gtest_import_library(GTest::gmock_main GMOCK_MAIN_LIBRARY "DEBUG")
+    endif()
+endif()

Tests/FindGTest/Test/CMakeLists.txt

@@ -16,3 +16,7 @@ add_executable(test_gtest_var main.cxx)
 target_include_directories(test_gtest_var PRIVATE ${GTEST_INCLUDE_DIRS})
 target_link_libraries(test_gtest_var PRIVATE ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
 add_test(NAME test_gtest_var COMMAND test_gtest_var)
+
+add_executable(test_gmock_tgt main.cxx)
+target_link_libraries(test_gmock_tgt GTest::gmock_main)
+add_test(NAME test_gmock_tgt COMMAND test_gmock_tgt)