From: Benjamin Barenblat <bbaren@google.com>
Subject: Support testing with a local googletest checkout
Forwarded: yes
Applied-Upstream: https://github.com/abseil/abseil-cpp/commit/bcefbdcdf6ad85046ccacee0aeffba5404d3e528

Debian likes doing dependency management manually, so add support for
testing against a local googletest checkout rather than one downloaded
from GitHub. Add an ABSL_LOCAL_GOOGLETEST_DIR variable that can be used
in conjunction with -DABSL_RUN_TESTS=ON -DABSL_USE_GOOGLETEST_HEAD=OFF
to specify the googletest location manually, and do a bit of related
cleanup.

This patch was originally submitted as
https://github.com/abseil/abseil-cpp/pull/628. Since the author works at
Google, upstream requested that he submit it internally. It was applied
as Piper revision 297677173 and exported to GitHub; the Applied-Upstream
URL above points to the exported commit.

--- a/CMake/Googletest/CMakeLists.txt.in
+++ b/CMake/Googletest/CMakeLists.txt.in
@@ -1,15 +1,26 @@
 cmake_minimum_required(VERSION 2.8.2)
 
-project(googletest-download NONE)
+project(googletest-external NONE)
 
 include(ExternalProject)
-ExternalProject_Add(googletest
-  GIT_REPOSITORY    https://github.com/google/googletest.git
-  GIT_TAG           master
-  SOURCE_DIR        "${CMAKE_BINARY_DIR}/googletest-src"
-  BINARY_DIR        "${CMAKE_BINARY_DIR}/googletest-build"
-  CONFIGURE_COMMAND ""
-  BUILD_COMMAND     ""
-  INSTALL_COMMAND   ""
-  TEST_COMMAND      ""
-)
\ No newline at end of file
+if(${ABSL_USE_GOOGLETEST_HEAD})
+  ExternalProject_Add(googletest
+    GIT_REPOSITORY    https://github.com/google/googletest.git
+    GIT_TAG           master
+    SOURCE_DIR        "${absl_gtest_src_dir}"
+    BINARY_DIR        "${absl_gtest_build_dir}"
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND     ""
+    INSTALL_COMMAND   ""
+    TEST_COMMAND      ""
+  )
+else()
+  ExternalProject_Add(googletest
+    SOURCE_DIR        "${absl_gtest_src_dir}"
+    BINARY_DIR        "${absl_gtest_build_dir}"
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND     ""
+    INSTALL_COMMAND   ""
+    TEST_COMMAND      ""
+  )
+endif()
\ No newline at end of file
--- a/CMake/Googletest/DownloadGTest.cmake
+++ b/CMake/Googletest/DownloadGTest.cmake
@@ -1,10 +1,11 @@
-# Downloads and unpacks googletest at configure time.  Based on the instructions
-# at https://github.com/google/googletest/tree/master/googletest#incorporating-into-an-existing-cmake-project
+# Integrates googletest at configure time.  Based on the instructions at
+# https://github.com/google/googletest/tree/master/googletest#incorporating-into-an-existing-cmake-project
 
-# Download the latest googletest from Github master
+# Set up the external googletest project, downloading the latest from Github
+# master if requested.
 configure_file(
   ${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt.in
-  ${CMAKE_BINARY_DIR}/googletest-download/CMakeLists.txt
+  ${CMAKE_BINARY_DIR}/googletest-external/CMakeLists.txt
 )
 
 set(ABSL_SAVE_CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
@@ -14,17 +15,17 @@ if (BUILD_SHARED_LIBS)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DGTEST_CREATE_SHARED_LIBRARY=1")
 endif()
 
-# Configure and build the downloaded googletest source
+# Configure and build the googletest source.
 execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
   RESULT_VARIABLE result
-  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-download )
+  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-external )
 if(result)
   message(FATAL_ERROR "CMake step for googletest failed: ${result}")
 endif()
 
 execute_process(COMMAND ${CMAKE_COMMAND} --build .
   RESULT_VARIABLE result
-  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-download)
+  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-external)
 if(result)
   message(FATAL_ERROR "Build step for googletest failed: ${result}")
 endif()
diff --git a/CMakeLists.txt b/CMakeLists.txt
index fdfb2cf..74b5cd9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -84,6 +84,10 @@
 option(ABSL_USE_GOOGLETEST_HEAD
   "If ON, abseil will download HEAD from googletest at config time." OFF)
 
+set(ABSL_LOCAL_GOOGLETEST_DIR "/usr/src/googletest" CACHE PATH
+  "If ABSL_USE_GOOGLETEST_HEAD is OFF, specifies the directory of a local googletest checkout."
+  )
+
 option(ABSL_RUN_TESTS "If ON, Abseil tests will be run." OFF)
 
 if(${ABSL_RUN_TESTS})
@@ -96,11 +100,13 @@
 ## check targets
 if(BUILD_TESTING)
 
+  set(absl_gtest_build_dir ${CMAKE_BINARY_DIR}/googletest-build)
   if(${ABSL_USE_GOOGLETEST_HEAD})
-    include(CMake/Googletest/DownloadGTest.cmake)
     set(absl_gtest_src_dir ${CMAKE_BINARY_DIR}/googletest-src)
-    set(absl_gtest_build_dir ${CMAKE_BINARY_DIR}/googletest-build)
+  else()
+    set(absl_gtest_src_dir ${ABSL_LOCAL_GOOGLETEST_DIR})
   endif()
+  include(CMake/Googletest/DownloadGTest.cmake)
 
   check_target(gtest)
   check_target(gtest_main)