CMake build: add a NLOHMANN_JSON_ORIGIN=auto/external/internal setting allowing to choose which nlohmann/json to use

Co-authored-by: Mike Taves <mwtoews@gmail.com>

11 files changed, 79 insertions, 6 deletions

diff --git a/.github/workflows/clang_linux/start.sh b/.github/workflows/clang_linux/start.sh
index a2b6c631..286fdb69 100755
--- a/.github/workflows/clang_linux/start.sh
+++ b/.github/workflows/clang_linux/start.sh
@@ -5,7 +5,7 @@ set -e
 apt-get update -y
 DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
     sudo autoconf automake libtool clang++-10 python3-clang-10 make cmake ccache pkg-config tar zip \
-    sqlite3 libsqlite3-dev libtiff-dev libcurl4-openssl-dev jq python3-pip
+    sqlite3 libsqlite3-dev libtiff-dev libcurl4-openssl-dev jq python3-pip nlohmann-json3-dev
 
 python3 -m pip install --user jsonschema
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 66c5027f..67a8d2e1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -122,8 +122,48 @@ include(ProjMac)
 include(policies)
 
 ################################################################################
+# Check for nlohmann_json
+################################################################################
+
+set(NLOHMANN_JSON_ORIGIN "auto" CACHE STRING
+"nlohmann/json origin. The default auto will try to use external \
+nlohmann/json if possible")
+set_property(CACHE NLOHMANN_JSON_ORIGIN PROPERTY STRINGS auto internal external)
+
+# Probably not the strictest minimum, but known to work with it
+set(MIN_NLOHMANN_JSON_VERSION 3.7.0)
+
+if(NLOHMANN_JSON_ORIGIN STREQUAL "external")
+  find_package(nlohmann_json REQUIRED)
+  set(NLOHMANN_JSON "external")
+elseif(NLOHMANN_JSON_ORIGIN STREQUAL "internal")
+  set(NLOHMANN_JSON "internal")
+else()
+  find_package(nlohmann_json QUIET)
+  if(nlohmann_json_FOUND)
+    set(NLOHMANN_JSON "external")
+  else()
+    set(NLOHMANN_JSON "internal")
+  endif()
+endif()
+
+if(NLOHMANN_JSON STREQUAL "external")
+  # Check minimum version
+  if(nlohmann_json_VERSION VERSION_LESS MIN_NLOHMANN_JSON_VERSION)
+    message(STATUS "external nlohmann/json version ${nlohmann_json_VERSION} "
+      "is older than minimum requirement ${MIN_NLOHMANN_JSON_VERSION}")
+    set(NLOHMANN_JSON "internal")
+  else()
+    message(STATUS "found nlohmann/json version ${nlohmann_json_VERSION}")
+  endif()
+endif()
+
+message(STATUS "nlohmann/json: ${NLOHMANN_JSON}")
+
+################################################################################
 # Check for sqlite3
 ################################################################################
+
 find_program(EXE_SQLITE3 sqlite3)
 if(NOT EXE_SQLITE3)
   message(SEND_ERROR "sqlite3 binary not found!")
diff --git a/configure.ac b/configure.ac
index 3e28bbf1..4ff2ad9f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -358,8 +358,10 @@ dnl ---------------------------------------------------------------------------
 dnl Generate files
 dnl ---------------------------------------------------------------------------
 
-AC_CONFIG_FILES([Makefile cmake/Makefile src/Makefile include/Makefile include/proj/Makefile include/proj/internal/Makefile
-                 include/proj/internal/nlohmann/Makefile
+AC_CONFIG_FILES([Makefile cmake/Makefile src/Makefile include/Makefile include/proj/Makefile
+                 include/proj/internal/Makefile
+                 include/proj/internal/vendor/Makefile
+                 include/proj/internal/vendor/nlohmann/Makefile
                  test/Makefile test/cli/Makefile test/gie/Makefile test/gigs/Makefile test/unit/Makefile
                  man/Makefile man/man1/Makefile data/Makefile])
 if ! test "x$with_external_gtest" = "xyes" ; then
diff --git a/include/proj/internal/Makefile.am b/include/proj/internal/Makefile.am
index 8e9edacf..b3fb57eb 100644
--- a/include/proj/internal/Makefile.am
+++ b/include/proj/internal/Makefile.am
@@ -1,4 +1,4 @@
-SUBDIRS = nlohmann
+SUBDIRS = vendor
 
 noinst_HEADERS = \
 	coordinatesystem_internal.hpp \
diff --git a/include/proj/internal/include_nlohmann_json.hpp b/include/proj/internal/include_nlohmann_json.hpp
index 68b6836d..6fa5cd2d 100644
--- a/include/proj/internal/include_nlohmann_json.hpp
+++ b/include/proj/internal/include_nlohmann_json.hpp
@@ -26,13 +26,26 @@
  * DEALINGS IN THE SOFTWARE.
  ****************************************************************************/
 
+#ifndef INCLUDE_NLOHMANN_JSON_HPP
+#define INCLUDE_NLOHMANN_JSON_HPP
+
 #if defined(__GNUC__)
 #pragma GCC system_header
 #endif
 
+#ifdef EXTERNAL_NLOHMANN_JSON
+
+#include <nlohmann/json.hpp>
+
+#else // !EXTERNAL_NLOHMANN_JSON
+
 // to avoid any clash if PROJ users have another version of nlohmann/json.hpp
 #define nlohmann proj_nlohmann
 
 #if !defined(DOXYGEN_ENABLED)
-#include "nlohmann/json.hpp"
+#include "vendor/nlohmann/json.hpp"
 #endif
+
+#endif // EXTERNAL_NLOHMANN_JSON
+
+#endif // INCLUDE_NLOHMANN_JSON_HPP
diff --git a/include/proj/internal/vendor/Makefile.am b/include/proj/internal/vendor/Makefile.am
new file mode 100644
index 00000000..7d8176b2
--- /dev/null
+++ b/include/proj/internal/vendor/Makefile.am
@@ -0,0 +1 @@
+SUBDIRS = nlohmann
diff --git a/include/proj/internal/nlohmann/Makefile.am b/include/proj/internal/vendor/nlohmann/Makefile.am
index eaf3200e..eaf3200e 100644
--- a/include/proj/internal/nlohmann/Makefile.am
+++ b/include/proj/internal/vendor/nlohmann/Makefile.am
diff --git a/include/proj/internal/nlohmann/json.hpp b/include/proj/internal/vendor/nlohmann/json.hpp
index a70aaf8c..a70aaf8c 100644
--- a/include/proj/internal/nlohmann/json.hpp
+++ b/include/proj/internal/vendor/nlohmann/json.hpp
diff --git a/src/bin_projsync.cmake b/src/bin_projsync.cmake
index e18eebd9..ea6bb09c 100644
--- a/src/bin_projsync.cmake
+++ b/src/bin_projsync.cmake
@@ -8,6 +8,11 @@ set_target_properties(bin_projsync
   OUTPUT_NAME projsync)
 target_link_libraries(bin_projsync PRIVATE ${PROJ_LIBRARIES})
 target_compile_options(bin_projsync PRIVATE ${PROJ_CXX_WARN_FLAGS})
+if(NLOHMANN_JSON STREQUAL "external")
+  target_compile_definitions(bin_projsync PRIVATE EXTERNAL_NLOHMANN_JSON)
+  target_link_libraries(bin_projsync PRIVATE nlohmann_json::nlohmann_json)
+endif()
+
 install(TARGETS bin_projsync
   RUNTIME DESTINATION ${BINDIR})
 
diff --git a/src/lib_proj.cmake b/src/lib_proj.cmake
index f4adb443..71468c87 100644
--- a/src/lib_proj.cmake
+++ b/src/lib_proj.cmake
@@ -293,7 +293,6 @@ include_directories(${PROJ_SOURCE_DIR}/include)
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 source_group("CMake Files" FILES CMakeLists.txt)
 
-
 # Embed PROJ_LIB data files location
 add_definitions(-DPROJ_LIB="${CMAKE_INSTALL_PREFIX}/${DATADIR}")
 
@@ -397,6 +396,11 @@ endif()
 target_include_directories(proj PRIVATE ${SQLITE3_INCLUDE_DIR})
 target_link_libraries(proj PRIVATE ${SQLITE3_LIBRARY})
 
+if(NLOHMANN_JSON STREQUAL "external")
+  target_compile_definitions(proj PRIVATE EXTERNAL_NLOHMANN_JSON)
+  target_link_libraries(proj PRIVATE nlohmann_json::nlohmann_json)
+endif()
+
 if(TIFF_ENABLED)
   target_compile_definitions(proj PRIVATE -DTIFF_ENABLED)
   target_include_directories(proj PRIVATE ${TIFF_INCLUDE_DIR})
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index 1a080ac5..53a14ced 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -166,6 +166,10 @@ add_executable(test_defmodel
 target_link_libraries(test_defmodel
   PRIVATE GTest::gtest
   PRIVATE ${PROJ_LIBRARIES})
+if(NLOHMANN_JSON STREQUAL "external")
+  target_compile_definitions(test_defmodel PRIVATE EXTERNAL_NLOHMANN_JSON)
+  target_link_libraries(test_defmodel PRIVATE nlohmann_json::nlohmann_json)
+endif()
 add_test(NAME test_defmodel COMMAND test_defmodel)
 set_property(TEST test_defmodel
   PROPERTY ENVIRONMENT ${PROJ_TEST_ENVIRONMENT})
@@ -176,6 +180,10 @@ add_executable(test_tinshift
 target_link_libraries(test_tinshift
   PRIVATE GTest::gtest
   PRIVATE ${PROJ_LIBRARIES})
+if(NLOHMANN_JSON STREQUAL "external")
+  target_compile_definitions(test_tinshift PRIVATE EXTERNAL_NLOHMANN_JSON)
+  target_link_libraries(test_tinshift PRIVATE nlohmann_json::nlohmann_json)
+endif()
 add_test(NAME test_tinshift COMMAND test_tinshift)
 set_property(TEST test_tinshift
   PROPERTY ENVIRONMENT ${PROJ_TEST_ENVIRONMENT})