It seems that we export too many targets. (#1385)

* It seems that we export too many targets.

* Adding missing word.

* Let us try this.

* Restoring dead line.

* Some fixes.

* Update src/CMakeLists.txt

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Update cmake/simdjson-config.nothread.cmake.in

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Update cmake/simdjson-config.cmake.in

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Update CMakeLists.txt

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Update CMakeLists.txt

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Removing useless file

* Simplifying the PR somewhat.

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

CMakeLists.txt

@@ -43,6 +43,14 @@ if(NOT(SIMDJSON_JUST_LIBRARY))
 endif()
 install(FILES singleheader/simdjson.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
+option(SIMDJSON_ENABLE_THREADS "Link with thread support" ON)
+include(CMakePackageConfigHelpers)
+configure_package_config_file("${PROJECT_SOURCE_DIR}/cmake/simdjson-config.cmake.in"
+      "${PROJECT_BINARY_DIR}/simdjson-config.cmake" 
+      INSTALL_DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/simdjson"
+      NO_SET_AND_CHECK_MACRO
+      NO_CHECK_REQUIRED_COMPONENTS_MACRO)
+
 #
 # Compile tools / tests / benchmarks
 #

cmake/simdjson-config.cmake.in

@@ -0,0 +1,9 @@
+@PACKAGE_INIT@
+
+include(CMakeFindDependencyMacro)
+if(@SIMDJSON_ENABLE_THREADS@)
+    set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+    find_dependency(Threads)
+endif()
+# Import targets.
+include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@-targets.cmake")

cmake/simdjson-flags.cmake

@@ -202,8 +202,6 @@ if(SIMDJSON_ENABLE_THREADS)
   set(THREADS_PREFER_PTHREAD_FLAG TRUE)
   find_package(Threads REQUIRED)
   target_link_libraries(simdjson-flags INTERFACE Threads::Threads)
-  target_link_libraries(simdjson-flags INTERFACE ${CMAKE_THREAD_LIBS_INIT})
-  target_compile_options(simdjson-flags INTERFACE ${CMAKE_THREAD_LIBS_INIT})
   target_compile_definitions(simdjson-flags INTERFACE SIMDJSON_THREADS_ENABLED=1) # This will be set in the code automatically.
 endif()
 
@@ -237,4 +235,6 @@ CHECK_SYMBOL_EXISTS(fork unistd.h HAVE_POSIX_FORK)
 CHECK_SYMBOL_EXISTS(wait sys/wait.h HAVE_POSIX_WAIT)
 
 install(TARGETS simdjson-flags EXPORT simdjson-config)
-install(TARGETS simdjson-internal-flags EXPORT simdjson-config)
+
+# I do not think we want to export our internal flags!
+# install(TARGETS simdjson-internal-flags EXPORT simdjson-config)

src/CMakeLists.txt

@@ -8,7 +8,12 @@
 add_library(simdjson-include-source INTERFACE)
 target_link_libraries(simdjson-include-source INTERFACE simdjson-headers)
 target_include_directories(simdjson-include-source INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
-install(TARGETS simdjson-include-source EXPORT simdjson-config)
+# If a CMake user installs simdjson and then does...
+#   find_package(simdjson CONFIG REQUIRED)
+#   find_package(Threads REQUIRED)
+#   target_link_libraries(test PRIVATE simdjson-include-source)
+# It is not clear what it should do? Does the user get access to the src files?
+# install(TARGETS simdjson-include-source EXPORT simdjson-config)
 
 #
 # For callers who intend to compile simdjson.cpp themselves.
@@ -19,7 +24,14 @@ install(TARGETS simdjson-include-source EXPORT simdjson-config)
 add_library(simdjson-source INTERFACE)
 target_sources(simdjson-source INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>/simdjson.cpp)
 target_link_libraries(simdjson-source INTERFACE simdjson-include-source)
-install(TARGETS simdjson-source EXPORT simdjson-config)
+# Note that simdjson.cpp is *not* installed so installing simdjson-include-source is not great.
+# If a CMake user installs simdjson and then does...
+#   find_package(simdjson CONFIG REQUIRED)
+#   find_package(Threads REQUIRED)
+#   target_link_libraries(test PRIVATE simdjson-source)
+# It might fail with  Cannot find source file: simdjson.cpp
+# See issue https://github.com/simdjson/simdjson/issues/1383
+# install(TARGETS simdjson-source EXPORT simdjson-config)
 
 #
 # simdjson is the distributed library compiled with flags.
@@ -31,7 +43,15 @@ install(TARGETS simdjson-source EXPORT simdjson-config)
 
 if(SIMDJSON_BUILD_STATIC)
   MESSAGE( STATUS "Building a static library." )
-  add_library(simdjson STATIC "")
+  ###
+  # In the case of a static library, if you do "target_link_libraries(simdjson PRIVATE simdjson-source simdjson-internal-flags)"
+  # without also calling "install(TARGETS simdjson-source EXPORT simdjson-config)" you get an error
+  # to the effect that you are trying to install 'simdjson' which depends on 'simdjson-source' while
+  # not installing 'simdjson-source', so it fails. So we bypass entirely simdjson-source since we do
+  # not want to install them.
+  ####
+  add_library(simdjson STATIC simdjson.cpp)
+  target_include_directories(simdjson PRIVATE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
 else()
   MESSAGE( STATUS "Building a dynamic library." )
   add_library(simdjson SHARED "")
@@ -40,10 +60,12 @@ else()
     MESSAGE( STATUS "Building a Windows DLL using Visual Studio, exporting all symbols automatically." )
     set_target_properties(simdjson PROPERTIES WINDOWS_EXPORT_ALL_SYMBOLS 1)
   endif()
+  ###
+  # Somehow, for a dynamic library, the next line is entirely fine (but not for a static one).
+  ###
+  target_link_libraries(simdjson PRIVATE simdjson-source simdjson-internal-flags)
 endif()
-
 target_link_libraries(simdjson PUBLIC simdjson-headers simdjson-flags) # Only expose the headers, not sources
-target_link_libraries(simdjson PRIVATE simdjson-source simdjson-internal-flags)
 
 ##
 ## In systems like R, libraries must not use stderr or abort to be acceptable.
@@ -119,7 +141,7 @@ install(TARGETS simdjson
 )
 
 install(EXPORT simdjson-config
-  FILE simdjson-config.cmake
+  FILE simdjson-targets.cmake
   NAMESPACE simdjson::
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/simdjson
 )