From 33a2154f8dbff1382d84d6e463e31a5ac9f3da18 Mon Sep 17 00:00:00 2001
From: Chuck Atkins <chuck.atkins@kitware.com>
Date: Mon, 9 Apr 2018 11:32:18 -0400
Subject: [PATCH] Enable target namespaces and build dir project config

CMake convention is to use a project namespace, i.e. Foo::, for imported
targets.  When multiple targets are imported from a project, this looks
like Foo::Bar1 Foo::Bar2, etc.  This adds the nlohmann_json:: namespace to
the exported target names.

This also allows the generated project config files to be used from the
build directory instead of just the install directory.
---
 CMakeLists.txt        | 11 +++++++++--
 cmake/config.cmake.in |  4 +++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9c8afbef..031a66f2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,9 +27,10 @@ set(NLOHMANN_JSON_CONFIG_INSTALL_DIR        "lib/cmake/${PROJECT_NAME}"
 set(NLOHMANN_JSON_INCLUDE_INSTALL_DIR       "include")
 set(NLOHMANN_JSON_TARGETS_EXPORT_NAME       "${PROJECT_NAME}Targets")
 set(NLOHMANN_JSON_CMAKE_CONFIG_TEMPLATE     "cmake/config.cmake.in")
-set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}/cmake_config")
+set(NLOHMANN_JSON_CMAKE_CONFIG_DIR          "${CMAKE_CURRENT_BINARY_DIR}")
 set(NLOHMANN_JSON_CMAKE_VERSION_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}ConfigVersion.cmake")
 set(NLOHMANN_JSON_CMAKE_PROJECT_CONFIG_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Config.cmake")
+set(NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE "${NLOHMANN_JSON_CMAKE_CONFIG_DIR}/${PROJECT_NAME}Targets.cmake")
 
 if (JSON_MultipleHeaders)
     set(NLOHMANN_JSON_INCLUDE_BUILD_DIR "${PROJECT_SOURCE_DIR}/include/")
@@ -44,7 +45,7 @@ endif()
 ## create target and add include path
 ##
 add_library(${NLOHMANN_JSON_TARGET_NAME} INTERFACE)
-
+add_library(${PROJECT_NAME}::${NLOHMANN_JSON_TARGET_NAME} ALIAS ${NLOHMANN_JSON_TARGET_NAME})
 target_compile_features(${NLOHMANN_JSON_TARGET_NAME} INTERFACE cxx_std_11)
 
 target_include_directories(
@@ -105,6 +106,11 @@ if (NLOHMANN_ADD_NATVIS)
         DESTINATION .
 )
 endif()
+export(
+    TARGETS ${NLOHMANN_JSON_TARGET_NAME}
+    NAMESPACE ${PROJECT_NAME}::
+    FILE ${NLOHMANN_JSON_CMAKE_PROJECT_TARGETS_FILE}
+)
 install(
     TARGETS ${NLOHMANN_JSON_TARGET_NAME}
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
@@ -112,5 +118,6 @@ install(
 )
 install(
     EXPORT ${NLOHMANN_JSON_TARGETS_EXPORT_NAME}
+    NAMESPACE ${PROJECT_NAME}::
     DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
 )
diff --git a/cmake/config.cmake.in b/cmake/config.cmake.in
index b4fd29d9..8baabf07 100644
--- a/cmake/config.cmake.in
+++ b/cmake/config.cmake.in
@@ -1,3 +1,5 @@
 @PACKAGE_INIT@
-include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
+if(NOT TARGET @PROJECT_NAME@::@NLOHMANN_JSON_TARGET_NAME@)
+    include("${CMAKE_CURRENT_LIST_DIR}/@NLOHMANN_JSON_TARGETS_EXPORT_NAME@.cmake")
+endif()
 check_required_components("@PROJECT_NAME@")