Make gtest optional.

[hpolloni]

Don't build s2testing if there's no GTEST.
Don't build examples if s2testing is not a target.

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[funchal]

Thanks for the patch! @hpolloni I guess you need to sign the CLA before this can be merged.

[figroc]

@hpolloni Would you kindly sign the CLA? I'm using your patch in my own build. But it would be great if it got merged in upstream. This is the patch I use:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5ecd280..c6b15ac 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -198,10 +198,6 @@ add_library(s2
             src/s2/util/math/exactfloat/exactfloat.cc
             src/s2/util/math/mathutil.cc
             src/s2/util/units/length-units.cc)
-add_library(s2testing STATIC
-            src/s2/s2builderutil_testing.cc
-            src/s2/s2shapeutil_testing.cc
-            src/s2/s2testing.cc)
 target_link_libraries(
     s2
     ${GFLAGS_LIBRARIES} ${GLOG_LIBRARIES} ${OPENSSL_LIBRARIES}
@@ -242,7 +238,6 @@ install(FILES src/s2/_fp_contract_off.h
               src/s2/s2builderutil_s2polyline_layer.h
               src/s2/s2builderutil_s2polyline_vector_layer.h
               src/s2/s2builderutil_snap_functions.h
-              src/s2/s2builderutil_testing.h
               src/s2/s2cap.h
               src/s2/s2cell.h
               src/s2/s2cell_id.h
@@ -319,9 +314,7 @@ install(FILES src/s2/_fp_contract_off.h
               src/s2/s2shapeutil_range_iterator.h
               src/s2/s2shapeutil_shape_edge.h
               src/s2/s2shapeutil_shape_edge_id.h
-              src/s2/s2shapeutil_testing.h
               src/s2/s2shapeutil_visit_crossing_edge_pairs.h
-              src/s2/s2testing.h
               src/s2/s2text_format.h
               src/s2/s2wedge_relations.h
               src/s2/sequence_lexicon.h
@@ -407,12 +400,21 @@ install(FILES src/s2/util/math/mathutil.h
 install(FILES src/s2/util/units/length-units.h
               src/s2/util/units/physical-units.h
         DESTINATION include/s2/util/units)
-install(TARGETS s2 s2testing DESTINATION lib)
+install(TARGETS s2 DESTINATION lib)
 
 message("GTEST_ROOT: ${GTEST_ROOT}")
 if (GTEST_ROOT)
+  add_library(s2testing STATIC
+              src/s2/s2builderutil_testing.cc
+              src/s2/s2shapeutil_testing.cc
+              src/s2/s2testing.cc)
   add_subdirectory(${GTEST_ROOT} build_gtest)
   include_directories(${GTEST_ROOT}/include)
+  install(FILES src/s2/s2builderutil_testing.h
+                src/s2/s2shapeutil_testing.h
+                src/s2/s2testing.h
+          DESTINATION include/s2)
+  install(TARGETS s2testing DESTINATION lib)
 
   set(S2TestFiles
       src/s2/encoded_s2cell_id_vector_test.cc
@@ -527,7 +529,7 @@ if (GTEST_ROOT)
   endforeach()
 endif()
 
-if (BUILD_EXAMPLES)
+if (BUILD_EXAMPLES AND TARGET s2testing)
   add_subdirectory("doc/examples" examples)
 endif()

[hpolloni]

Hi, I have signed the CLA two times.

Individual agreements we have on file for you:

Google Individual CLA	Herman Polloni	Aug 03, 2019 23:24 PDT	Edit Contact Information

Should I sign it again?

[figroc]

Maybe you have to @googlebot?

As in your commit, there are 3 testing header files unnecessarily installed when GTEST_ROOT is not set.

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[jmr]

Sorry I lost this. I'll merge this if it still works with against head.

[jmr]

There are additional _testing.cc files that include gunit now.

[jmr]

two space indent

[jmr]

Obsoleted by #236