Added support for header-only libraries

cmake/Platform/Targets/ArduinoCMakeLibraryTarget.cmake

@@ -6,9 +6,20 @@
 #=============================================================================#
 function(_set_library_flags _library_target _board_id)
 
+    set(scope_options "PRIVATE" "PUBLIC" "INTERFACE")
+    cmake_parse_arguments(parsed_args "${scope_options}" "" "" ${ARGN})
+
+    if (parsed_args_PRIVATE)
+        set(scope PRIVATE)
+    elseif (parsed_args_INTERFACE)
+        set(scope INTERFACE)
+    else ()
+        set(scope PUBLIC)
+    endif ()
+
     # Set C++ compiler flags
     get_cmake_compliant_language_name(cpp flags_language)
-    set_compiler_target_flags(${_library_target} "${_board_id}" PUBLIC LANGUAGE ${flags_language})
+    set_compiler_target_flags(${_library_target} "${_board_id}" ${scope} LANGUAGE ${flags_language})
 
     # Set linker flags
     set_linker_flags(${_library_target} "${_board_id}")
@@ -22,37 +33,45 @@ endfunction()
 #       _target_name - Name of the library target to be created. Usually library's real name.
 #       _board_id - Board ID associated with the linked Core Lib.
 #       _sources - Source and header files to create library target from.
-#       [ARCH] - Optional library architecture (Such as 'avr', 'nrf52', etc.)
+#       [ARCH] - Optional library architecture (Such as 'avr', 'nrf52', etc.).
+#       [INTERFACE] - Whether the library should be created as an interface library (header-only).
 #=============================================================================#
 function(_add_arduino_cmake_library _target_name _board_id _sources)
 
-    cmake_parse_arguments(library "" "ARCH" "" ${ARGN})
+    cmake_parse_arguments(parsed_args "INTERFACE" "ARCH" "" ${ARGN})
 
-    if (library_ARCH) # Treat architecture-specific libraries differently
+    if (parsed_args_ARCH) # Treat architecture-specific libraries differently
         # Filter any sources that aren't supported by the platform's architecture
         list(LENGTH library_ARCH num_of_libs_archs)
         if (${num_of_libs_archs} GREATER 1)
             # Exclude all unsupported architectures, request filter in regex mode
-            _get_unsupported_architectures("${library_ARCH}" arch_filter REGEX)
+            _get_unsupported_architectures("${parsed_args_ARCH}" arch_filter REGEX)
             set(filter_type EXCLUDE)
         else ()
-            set(arch_filter "src\\/[^/]+\\.|${library_ARCH}")
+            set(arch_filter "src\\/[^/]+\\.|${parsed_args_ARCH}")
             set(filter_type INCLUDE)
         endif ()
         list(FILTER _sources ${filter_type} REGEX ${arch_filter})
     endif ()
 
-    add_library(${_target_name} STATIC "${_sources}")
+    if (parsed_args_INTERFACE)
+        add_library(${_target_name} INTERFACE)
+        set(scope INTERFACE)
+    else ()
+        add_library(${_target_name} STATIC "${_sources}")
+        set(scope PUBLIC)
+    endif ()
+
     # Treat headers' parent directories as include directories of the target
     get_headers_parent_directories("${_sources}" include_dirs)
-    target_include_directories(${_target_name} PUBLIC ${include_dirs})
+    target_include_directories(${_target_name} ${scope} ${include_dirs})
 
-    _set_library_flags(${_target_name} ${_board_id})
+    _set_library_flags(${_target_name} ${_board_id} ${scope})
 
-    if (library_ARCH)
-        string(TOUPPER ${library_ARCH} upper_arch)
+    if (parsed_args_ARCH)
+        string(TOUPPER ${parsed_args_ARCH} upper_arch)
         set(arch_definition "ARDUINO_ARCH_${upper_arch}")
-        target_compile_definitions(${_target_name} PUBLIC ${arch_definition})
+        target_compile_definitions(${_target_name} ${scope} ${arch_definition})
     endif ()
 
 endfunction()
@@ -76,6 +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})
@@ -84,17 +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} ${_library_name})
+    target_link_libraries(${_target_name} PRIVATE ${_library_name})
 
 endfunction()

cmake/Platform/Targets/ArduinoLibraryTarget.cmake

@@ -86,6 +86,15 @@ function(add_arduino_library _target_name _board_id _sources)
 
 endfunction()
 
+function(add_arduino_header_only_library _target_name _board_id)
+
+    cmake_parse_arguments(parsed_args "ARCH" "" "HEADERS" ${ARGN})
+
+    _add_arduino_cmake_library(${_target_name} ${_board_id} "${parsed_args_HEADERS}"
+            INTERFACE ${parsed_args_ARCH})
+
+endfunction()
+
 #=============================================================================#
 # Finds an Arduino library with the given library name and creates a library target from it
 # with the given target name.
@@ -95,12 +104,14 @@ endfunction()
 #       _library_name - Name of the Arduino library to find.
 #       _board_id - Board ID associated with the linked Core Lib.
 #       [3RD_PARTY] - Whether library should be treated as a 3rd Party library.
+#       [HEADER_ONLY] - Whether library is a header-only library, i.e has no source files
 #=============================================================================#
 function(find_arduino_library _target_name _library_name _board_id)
 
-    cmake_parse_arguments(find_lib "3RD_PARTY" "" "" ${ARGN})
+    set(argument_options "3RD_PARTY" "HEADER_ONLY")
+    cmake_parse_arguments(parsed_args "${argument_options}" "" "" ${ARGN})
 
-    if (NOT find_lib_3RD_PARTY)
+    if (NOT parsed_args_3RD_PARTY)
         convert_string_to_pascal_case(${_library_name} _library_name)
     endif ()
 
@@ -130,13 +141,23 @@ function(find_arduino_library _target_name _library_name _board_id)
             set(error_message "Couldn't find any header files for the ${_library_name} library")
             message(SEND_ERROR "${error_message}")
         else ()
-            find_library_source_files("${library_path}" library_sources)
-            if (NOT library_sources)
-                set(error_message "Couldn't find any source files for the ${_library_name} library")
-                message(SEND_ERROR "${error_message}")
+            if (parsed_args_HEADER_ONLY)
+                add_arduino_header_only_library(${_target_name} ${_board_id}
+                        ARCH ${lib_arch}
+                        HEADERS ${library_headers})
             else ()
-                set(sources ${library_headers} ${library_sources})
-                add_arduino_library(${_target_name} ${_board_id} "${sources}" ARCH ${lib_arch})
+                find_library_source_files("${library_path}" library_sources)
+                if (NOT library_sources)
+                    string(CONCAT error_message
+                            "Couldn't find any source files for the ${_library_name} library - "
+                            "Is it a header-only library?\n"
+                            "If so, please pass the HEADER_ONLY option as an argument to the function")
+                    message(SEND_ERROR "${error_message}")
+                else ()
+                    set(sources ${library_headers} ${library_sources})
+                    add_arduino_library(${_target_name} ${_board_id} "${sources}"
+                            ARCH ${lib_arch})
+                endif ()
             endif ()
         endif ()
     endif ()
@@ -151,9 +172,12 @@ 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})
@@ -164,8 +188,14 @@ 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/3rd_party.cpp

@@ -0,0 +1,14 @@
+#include <Arduino.h>
+#include "NeoPixelTest.hpp"
+#include "GFXTest.h"
+
+void setup()
+{
+    testNeoPixel();
+    testGFX();
+}
+
+void loop()
+{
+
+}

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

@@ -3,17 +3,23 @@ cmake_minimum_required(VERSION 3.8.2)
 project(3rd_Party_Arduino_Library)
 get_board_id(board_id nano atmega328)
 
-add_arduino_executable(3rd_Party_Arduino_Library ${board_id} NeoPixelTest.cpp GFXTest.cpp)
+# First, declare and create our executable - It'll use 4 sources
+add_arduino_executable(3rd_Party_Arduino_Library ${board_id} 3rd_party.cpp
+        NeoPixelTest.cpp GFXTest.cpp)
 target_include_directories(3rd_Party_Arduino_Library PRIVATE include)
 
+# Add the "NeoPixel" library manually using the library addition API
 add_arduino_library(Adafruit_NeoPixel ${board_id} libraries/Adafruit_NeoPixel/Adafruit_NeoPixel.cpp)
 target_include_directories(Adafruit_NeoPixel PUBLIC libraries/Adafruit_NeoPixel)
 
-# 'Trick' the framework to use current directory as Sketchbook, allowing us to use the 'find' API
+# Find the "GFX" library by 'tricking' the framework to use current directory as the Sketchbook path,
+# allowing us to use the 'find' API
 set(ARDUINO_CMAKE_SKETCHBOOK_PATH "${CMAKE_CURRENT_LIST_DIR}")
 find_arduino_library(Adafruit_GFX Adafruit-GFX-Library ${board_id} 3RD_PARTY)
-target_source_directories(Adafruit_GFX
-        DIRS libraries/Adafruit-GFX-Library/Fonts)
+# We can also explicitly add additional directories to the target,
+# as only root dir and 'src' sub-dir are added by default
+target_source_directories(Adafruit_GFX DIRS libraries/Adafruit-GFX-Library/Fonts)
 
+# 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})

examples/3rd-party-library/GFXTest.cpp

@@ -2,7 +2,7 @@
 
 static Adafruit_GFX_Button gfxButton;
 
-void doSomething()
+void testGFX()
 {
     gfxButton.isPressed();
 }

examples/3rd-party-library/NeoPixelTest.cpp

@@ -1,15 +1,11 @@
-#include <Adafruit_NeoPixel.h>
-#include "GFXTest.h"
+
+#include <NeoPixelTest.hpp>
+
+#include "include/NeoPixelTest.hpp"
 
 Adafruit_NeoPixel neoPixel;
 
-void setup()
+void testNeoPixel()
 {
     neoPixel.clear();
-    doSomething();
-}
-
-void loop()
-{
-
 }

examples/3rd-party-library/include/GFXTest.h

@@ -3,6 +3,6 @@
 
 #include <Adafruit_GFX.h>
 
-void doSomething();
+void testGFX();
 
 #endif //EXAMPLES_GFXTEST_HPP

examples/3rd-party-library/include/NeoPixelTest.hpp

@@ -0,0 +1,8 @@
+#ifndef EXAMPLES_NEOPIXELTEST_HPP
+#define EXAMPLES_NEOPIXELTEST_HPP
+
+#include <Adafruit_NeoPixel.h>
+
+void testNeoPixel();
+
+#endif //EXAMPLES_NEOPIXELTEST_HPP

examples/CMakeLists.txt

@@ -5,6 +5,7 @@ project(Examples LANGUAGES C CXX ASM)
 add_subdirectory(hello-world)
 add_subdirectory(arduino-library)
 add_subdirectory(3rd-party-library)
+add_subdirectory(header-only-library)
 add_subdirectory(blink-example)
 add_subdirectory(servo-knob-example)
 add_subdirectory(sketch)

examples/header-only-library/CMakeLists.txt

@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.8.2)
+
+project(Header_Only_Lib)
+get_board_id(board_id nano atmega328)
+
+add_arduino_executable(Header_Only_Lib ${board_id} headerOnlyTest.cpp)
+
+# Find the library by 'tricking' the framework to use current directory as the Sketchbook path,
+# allowing us to use the 'find' API
+set(ARDUINO_CMAKE_SKETCHBOOK_PATH "${CMAKE_CURRENT_LIST_DIR}")
+find_arduino_library(headerTest test-lib ${board_id} 3RD_PARTY HEADER_ONLY)
+
+link_arduino_library(Header_Only_Lib headerTest ${board_id} HEADER_ONLY)

examples/header-only-library/headerOnlyTest.cpp

@@ -0,0 +1,18 @@
+#include <Arduino.h>
+#include <TestLib.hpp>
+
+void setup()
+{
+    pinMode(BAR, OUTPUT);
+}
+
+void loop()
+{
+    foo();
+    delayMicroseconds(SOME_DELAY);
+}
+
+void foo()
+{
+    digitalWrite(BAR, HIGH);
+}

examples/header-only-library/libraries/test-lib/library.properties

@@ -0,0 +1,9 @@
+name=Test Library
+version=0.1
+author=Arduino-CMake-NG
+maintainer=Arduino-CMake-NG <https://github.com/arduino-cmake/Arduino-CMake-NG>
+sentence=Arduino library to test header-only feature support in the Arduino-CMake framework
+paragraph=Arduino library to test header-only feature support in the Arduino-CMake framework
+category=Display
+url=https://github.com/arduino-cmake/Arduino-CMake-NG
+architectures=*

examples/header-only-library/libraries/test-lib/src/TestLib.hpp

@@ -0,0 +1,11 @@
+#ifndef EXAMPLES_TESTLIB_HPP
+#define EXAMPLES_TESTLIB_HPP
+
+#include <Arduino.h>
+
+#define BAR 1
+#define SOME_DELAY 200
+
+void foo();
+
+#endif //EXAMPLES_TESTLIB_HPP