From 2969393afa32591123e710b10be043937a0af18c Mon Sep 17 00:00:00 2001
From: Patrick Boettcher <p@yai.se>
Date: Mon, 27 Jan 2020 11:06:24 +0100
Subject: [PATCH] fix / workaround for #79

---
 CMakeLists.txt | 75 +++++++++++++++++++++++++++++---------------------
 1 file changed, 43 insertions(+), 32 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 20ea426..5c809d7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,6 +29,10 @@ set_target_properties(nlohmann_json_schema_validator
                           VERSION ${PROJECT_VERSION}
                           SOVERSION 1)
 
+# if used as a sub-directory, do not create install-rules -
+# because of the dependency to nlohmann_json.
+set(JSON_VALIDATOR_INSTALL ON)
+
 # here we decice how nlohmann::json is found and used to build this project
 
 # first, check whether a nlohmann_json::nlohmann_json target exists already
@@ -39,11 +43,15 @@ if(TARGET nlohmann_json::nlohmann_json)
         nlohmann_json_schema_validator
         PUBLIC nlohmann_json::nlohmann_json)
 
+    set(JSON_VALIDATOR_INSTALL OFF)
+
 elseif(TARGET nlohmann_json) # or nlohmann_json, we are used a sub-project next to nlohmann-json's git repo
     message(STATUS "Found nlohmann_json-target - linking with it")
     target_link_libraries(
         nlohmann_json_schema_validator
         PUBLIC nlohmann_json)
+    set(JSON_VALIDATOR_INSTALL OFF)
+
 else()
     if (NOT IS_ABSOLUTE ${nlohmann_json_DIR}) # make nlohmann_json_DIR absolute
         get_filename_component(nlohmann_json_DIR
@@ -113,14 +121,16 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     endif()
 endif()
 
-install(TARGETS nlohmann_json_schema_validator
-        EXPORT ${PROJECT_NAME}Targets
-        LIBRARY DESTINATION lib
-        ARCHIVE DESTINATION lib
-        RUNTIME DESTINATION bin)
+if(JSON_VALIDATOR_INSTALL)
+    install(TARGETS nlohmann_json_schema_validator
+            EXPORT ${PROJECT_NAME}Targets
+            LIBRARY DESTINATION lib
+            ARCHIVE DESTINATION lib
+            RUNTIME DESTINATION bin)
 
-install(FILES src/nlohmann/json-schema.hpp
-        DESTINATION include/nlohmann)
+    install(FILES src/nlohmann/json-schema.hpp
+            DESTINATION include/nlohmann)
+endif()
 
 if (BUILD_EXAMPLES)
     # simple nlohmann_json_schema_validator-executable
@@ -139,35 +149,36 @@ if (BUILD_TESTS)
     enable_testing()
     add_subdirectory(test)
 endif()
-#---------------------------------------------------------------------------##
-# Set Up the Project Targets and Config Files for CMake
-#---------------------------------------------------------------------------##
 
-# Set the install path to the cmake config files
-set(INSTALL_CMAKE_DIR ${CMAKE_INSTALL_PREFIX}/lib/cmake/${PROJECT_NAME})
+if(JSON_VALIDATOR_INSTALL)
+    # Set Up the Project Targets and Config Files for CMake
 
-# Create the ConfigVersion file
-include(CMakePackageConfigHelpers) # write_basic_package_version_file
-write_basic_package_version_file( ${PROJECT_NAME}ConfigVersion.cmake
-                                  VERSION ${PACKAGE_VERSION}
-                                  COMPATIBILITY SameMajorVersion)
+    # Set the install path to the cmake config files
+    set(INSTALL_CMAKE_DIR ${CMAKE_INSTALL_PREFIX}/lib/cmake/${PROJECT_NAME})
 
-# Get the relative path from the INSTALL_CMAKE_DIR to the include directory
-file(RELATIVE_PATH REL_INCLUDE_DIR "${INSTALL_CMAKE_DIR}" "${CMAKE_INSTALL_PREFIX}/include")
+    # Create the ConfigVersion file
+    include(CMakePackageConfigHelpers) # write_basic_package_version_file
+    write_basic_package_version_file( ${PROJECT_NAME}ConfigVersion.cmake
+                                      VERSION ${PACKAGE_VERSION}
+                                      COMPATIBILITY SameMajorVersion)
+
+    # Get the relative path from the INSTALL_CMAKE_DIR to the include directory
+    file(RELATIVE_PATH REL_INCLUDE_DIR "${INSTALL_CMAKE_DIR}" "${CMAKE_INSTALL_PREFIX}/include")
 
 
-# Configure the Config.cmake file with the proper include directory
-set(CONF_INCLUDE_DIRS "\${JSON_SCHEMA_VALIDATOR_CMAKE_DIR}/${REL_INCLUDE_DIR}")
-configure_file(${PROJECT_NAME}Config.cmake.in
-               "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake" @ONLY)
+    # Configure the Config.cmake file with the proper include directory
+    set(CONF_INCLUDE_DIRS "\${JSON_SCHEMA_VALIDATOR_CMAKE_DIR}/${REL_INCLUDE_DIR}")
+    configure_file(${PROJECT_NAME}Config.cmake.in
+                   "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake" @ONLY)
 
-# Install the Config.cmake and ConfigVersion.cmake files
-install(FILES
-        "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
-        "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
-        DESTINATION "${INSTALL_CMAKE_DIR}")
+    # Install the Config.cmake and ConfigVersion.cmake files
+    install(FILES
+            "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+            "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+            DESTINATION "${INSTALL_CMAKE_DIR}")
 
-# Install Targets
-install(EXPORT ${PROJECT_NAME}Targets
-        FILE ${PROJECT_NAME}Targets.cmake
-        DESTINATION "${INSTALL_CMAKE_DIR}")
+    # Install Targets
+    install(EXPORT ${PROJECT_NAME}Targets
+            FILE ${PROJECT_NAME}Targets.cmake
+            DESTINATION "${INSTALL_CMAKE_DIR}")
+endif()