From e73f5791bf0da2f5600bb644f8176618524563ea Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Fri, 8 Mar 2019 22:46:43 -0800
Subject: [PATCH] cmake: add option to use system rapidjson if exists

---
 CMakeLists.txt | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 993376d8..8277d394 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,7 @@ include(DefaultCMakeBuildType)
 # Required Clang version
 option(LLVM_ENABLE_RTTI "-fno-rtti if OFF. This should match LLVM libraries" OFF)
 option(USE_SHARED_LLVM "Link against libLLVM.so instead separate LLVM{Option,Support,...}" OFF)
+option(USE_SYSTEM_RAPIDJSON "Use system RapidJSON instead of the git submodule if exists" ON)
 
 # Sources for the executable are specified at end of CMakeLists.txt
 add_executable(ccls "")
@@ -95,9 +96,15 @@ target_compile_definitions(ccls PRIVATE
 ### Includes
 
 target_include_directories(ccls PRIVATE src)
-target_include_directories(ccls SYSTEM PRIVATE
-                           third_party
-                           third_party/rapidjson/include)
+target_include_directories(ccls SYSTEM PRIVATE third_party)
+
+if(USE_SYSTEM_RAPIDJSON)
+  find_package(RapidJSON QUIET)
+endif()
+if(NOT RapidJSON_FOUND)
+  set(RapidJSON_INCLUDE_DIRS third_party/rapidjson/include)
+endif()
+target_include_directories(ccls SYSTEM PRIVATE ${RapidJSON_INCLUDE_DIRS})
 
 ### Install