From 27c6da933ec1dd4028bb80e4adf2fa7309ef4a04 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 20 Jan 2015 10:31:13 -0500
Subject: Add option to build CMake against a system jsoncpp

Create a CMAKE_USE_SYSTEM_JSONCPP option.
---
 CMakeLists.txt                | 23 ++++++++++++++++++++---
 Source/CMakeLists.txt         |  2 +-
 Utilities/cmThirdParty.h.in   |  1 +
 Utilities/cm_jsoncpp_reader.h |  7 ++++++-
 Utilities/cm_jsoncpp_value.h  |  7 ++++++-
 Utilities/cm_jsoncpp_writer.h |  7 ++++++-
 6 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d3c424b..bdc160d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,7 +65,7 @@ macro(CMAKE_HANDLE_SYSTEM_LIBRARIES)
 
   # Allow the user to enable/disable all system utility library options by
   # defining CMAKE_USE_SYSTEM_LIBRARIES or CMAKE_USE_SYSTEM_LIBRARY_${util}.
-  set(UTILITIES BZIP2 CURL EXPAT FORM LIBARCHIVE LIBLZMA ZLIB)
+  set(UTILITIES BZIP2 CURL EXPAT FORM JSONCPP LIBARCHIVE LIBLZMA ZLIB)
   foreach(util ${UTILITIES})
     if(NOT DEFINED CMAKE_USE_SYSTEM_LIBRARY_${util}
         AND DEFINED CMAKE_USE_SYSTEM_LIBRARIES)
@@ -104,6 +104,7 @@ macro(CMAKE_HANDLE_SYSTEM_LIBRARIES)
   CMAKE_DEPENDENT_OPTION(CMAKE_USE_SYSTEM_LIBLZMA "Use system-installed liblzma"
     "${CMAKE_USE_SYSTEM_LIBRARY_LIBLZMA}" "NOT CMAKE_USE_SYSTEM_LIBARCHIVE" ON)
   option(CMAKE_USE_SYSTEM_FORM "Use system-installed libform" "${CMAKE_USE_SYSTEM_LIBRARY_FORM}")
+  option(CMAKE_USE_SYSTEM_JSONCPP "Use system-installed jsoncpp" "${CMAKE_USE_SYSTEM_LIBRARY_JSONCPP}")
 
   # Mention to the user what system libraries are being used.
   foreach(util ${UTILITIES})
@@ -373,8 +374,24 @@ macro (CMAKE_BUILD_UTILITIES)
 
   #---------------------------------------------------------------------
   # Build jsoncpp library.
-  add_subdirectory(Utilities/cmjsoncpp)
-  CMAKE_SET_TARGET_FOLDER(cmjsoncpp "Utilities/3rdParty")
+  if(CMAKE_USE_SYSTEM_JSONCPP)
+    if(EXISTS ${CMAKE_ROOT}/Modules/FindJsonCpp.cmake)
+      find_package(JsonCpp)
+    elseif(NOT CMAKE_VERSION VERSION_LESS 3.0)
+      include(${CMake_SOURCE_DIR}/Modules/FindJsonCpp.cmake)
+    else()
+      message(FATAL_ERROR "CMAKE_USE_SYSTEM_JSONCPP requires CMake >= 3.0")
+    endif()
+    if(NOT JsonCpp_FOUND)
+      message(FATAL_ERROR
+        "CMAKE_USE_SYSTEM_JSONCPP is ON but a JsonCpp is not found!")
+    endif()
+    set(CMAKE_JSONCPP_LIBRARIES JsonCpp::JsonCpp)
+  else()
+    set(CMAKE_JSONCPP_LIBRARIES cmjsoncpp)
+    add_subdirectory(Utilities/cmjsoncpp)
+    CMAKE_SET_TARGET_FOLDER(cmjsoncpp "Utilities/3rdParty")
+  endif()
 
   #---------------------------------------------------------------------
   # Build XMLRPC library for CMake and CTest.
diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 435b654..af4c7cf 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -503,7 +503,7 @@ target_link_libraries(CMakeLib cmsys
   ${CMAKE_EXPAT_LIBRARIES} ${CMAKE_ZLIB_LIBRARIES}
   ${CMAKE_TAR_LIBRARIES} ${CMAKE_COMPRESS_LIBRARIES}
   ${CMAKE_CURL_LIBRARIES}
-  cmjsoncpp
+  ${CMAKE_JSONCPP_LIBRARIES}
   )
 
 # On Apple we need CoreFoundation
diff --git a/Utilities/cmThirdParty.h.in b/Utilities/cmThirdParty.h.in
index b883284..0cb6809 100644
--- a/Utilities/cmThirdParty.h.in
+++ b/Utilities/cmThirdParty.h.in
@@ -20,6 +20,7 @@
 #cmakedefine CMAKE_USE_SYSTEM_LIBARCHIVE
 #cmakedefine CMAKE_USE_SYSTEM_LIBLZMA
 #cmakedefine CMAKE_USE_SYSTEM_FORM
+#cmakedefine CMAKE_USE_SYSTEM_JSONCPP
 #cmakedefine CTEST_USE_XMLRPC
 
 #endif
diff --git a/Utilities/cm_jsoncpp_reader.h b/Utilities/cm_jsoncpp_reader.h
index d7cb50e..22f2d81 100644
--- a/Utilities/cm_jsoncpp_reader.h
+++ b/Utilities/cm_jsoncpp_reader.h
@@ -13,6 +13,11 @@
 #define cm_jsoncpp_reader_h
 
 /* Use the jsoncpp library configured for CMake.  */
-#include <cmjsoncpp/include/json/reader.h>
+#include "cmThirdParty.h"
+#ifdef CMAKE_USE_SYSTEM_JSONCPP
+# include <json/reader.h>
+#else
+# include <cmjsoncpp/include/json/reader.h>
+#endif
 
 #endif
diff --git a/Utilities/cm_jsoncpp_value.h b/Utilities/cm_jsoncpp_value.h
index 15e1088..b4cf620 100644
--- a/Utilities/cm_jsoncpp_value.h
+++ b/Utilities/cm_jsoncpp_value.h
@@ -13,6 +13,11 @@
 #define cm_jsoncpp_value_h
 
 /* Use the jsoncpp library configured for CMake.  */
-#include <cmjsoncpp/include/json/value.h>
+#include "cmThirdParty.h"
+#ifdef CMAKE_USE_SYSTEM_JSONCPP
+# include <json/value.h>
+#else
+# include <cmjsoncpp/include/json/value.h>
+#endif
 
 #endif
diff --git a/Utilities/cm_jsoncpp_writer.h b/Utilities/cm_jsoncpp_writer.h
index c410369..c99a0d0 100644
--- a/Utilities/cm_jsoncpp_writer.h
+++ b/Utilities/cm_jsoncpp_writer.h
@@ -13,6 +13,11 @@
 #define cm_jsoncpp_writer_h
 
 /* Use the jsoncpp library configured for CMake.  */
-#include <cmjsoncpp/include/json/writer.h>
+#include "cmThirdParty.h"
+#ifdef CMAKE_USE_SYSTEM_JSONCPP
+# include <json/writer.h>
+#else
+# include <cmjsoncpp/include/json/writer.h>
+#endif
 
 #endif
-- 
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