Completed missing linkage support for header-only libraries.

However, the feature isn't ready yet since it doesn't compile.

Author: MrPointer

cmake/Platform/Targets/ArduinoCMakeLibraryTarget.cmake

@@ -95,6 +95,15 @@ function(_link_arduino_cmake_library _target_name _library_name)
     set(scope_options "PRIVATE" "PUBLIC" "INTERFACE")
     cmake_parse_arguments(link_library "${scope_options}" "BOARD_CORE_TARGET" "" ${ARGN})
 
+    # Now, link library to executable
+    if (link_library_PUBLIC)
+        set(scope PUBLIC)
+    elseif (link_library_INTERFACE)
+        set(scope INTERFACE)
+    else ()
+        set(scope PRIVATE)
+    endif ()
+
     # First, include core lib's directories in library as well
     if (link_library_BOARD_CORE_TARGET)
         set(core_target ${link_library_BOARD_CORE_TARGET})
@@ -103,17 +112,9 @@ function(_link_arduino_cmake_library _target_name _library_name)
     endif ()
 
     get_target_property(core_lib_includes ${core_target} INCLUDE_DIRECTORIES)
-    target_include_directories(${_library_name} PUBLIC "${core_lib_includes}")
-    target_link_libraries(${_library_name} PUBLIC ${core_target})
+    target_include_directories(${_library_name} ${scope} "${core_lib_includes}")
+    target_link_libraries(${_library_name} ${scope} ${core_target})
 
-    # Now, link library to executable
-    if (link_library_PUBLIC)
-        set(scope PUBLIC)
-    elseif (link_library_INTERFACE)
-        set(scope INTERFACE)
-    else ()
-        set(scope PRIVATE)
-    endif ()
     target_link_libraries(${_target_name} ${scope} ${_library_name})
 
 endfunction()

cmake/Platform/Targets/ArduinoLibraryTarget.cmake

@@ -167,9 +167,12 @@ endfunction()
 #       _target_name - Name of the "executable" target.
 #       _library_target_name - Name of the library target.
 #       _board_id - Board ID associated with the linked Core Lib.
+#       [HEADER_ONLY] - Whether library is a header-only library, i.e has no source files
 #=============================================================================#
 function(link_arduino_library _target_name _library_target_name _board_id)
 
+    cmake_parse_arguments(parsed_args "HEADER_ONLY" "" "" ${ARGN})
+
     get_core_lib_target_name(${_board_id} core_lib_target)
 
     if (NOT TARGET ${_target_name})
@@ -180,8 +183,14 @@ function(link_arduino_library _target_name _library_target_name _board_id)
         message(FATAL_ERROR "Core Library target doesn't exist. This is bad and should be reported")
     endif ()
 
-    _link_arduino_cmake_library(${_target_name} ${_library_target_name}
-            PUBLIC
-            BOARD_CORE_TARGET ${core_lib_target})
+    if (parsed_args_HEADER_ONLY)
+        _link_arduino_cmake_library(${_target_name} ${_library_target_name}
+                INTERFACE
+                BOARD_CORE_TARGET ${core_lib_target})
+    else ()
+        _link_arduino_cmake_library(${_target_name} ${_library_target_name}
+                PUBLIC
+                BOARD_CORE_TARGET ${core_lib_target})
+    endif ()
 
 endfunction()

examples/3rd-party-library/CMakeLists.txt

@@ -26,4 +26,4 @@ find_arduino_library(EnableInterrupt EnableInterrupt ${board_id} 3RD_PARTY HEADE
 # Link all libraries to our previously created target
 link_arduino_library(3rd_Party_Arduino_Library Adafruit_NeoPixel ${board_id})
 link_arduino_library(3rd_Party_Arduino_Library Adafruit_GFX ${board_id})
-link_arduino_library(3rd_Party_Arduino_Library EnableInterrupt ${board_id})
+link_arduino_library(3rd_Party_Arduino_Library EnableInterrupt ${board_id} HEADER_ONLY)