Improvements to external component/module support.

Based on feedback from @tomsci - thanks!

components/modules/project_include.cmake

@@ -0,0 +1,22 @@
+# Helper functions for external module registration.
+# - extmod_register_conditional() for modules with a Kconfig option
+# - extmod_register_unconditional() for always-enabled modules
+
+function(extmod_register_conditional confname)
+  if (${CONFIG_NODEMCU_CMODULE_${confname}})
+    # If the module is enabled in menuconfig, add the linker option
+    # "-u <confname>_module_selected1" to make the linker include this
+    # module. See components/core/include/module.h for further details
+    # on how this works.
+    message("Including external module ${confname}")
+    target_link_libraries(${COMPONENT_LIB} "-u ${confname}_module_selected1")
+  endif()
+endfunction()
+
+function(extmod_register_unconditional confname)
+  message("Including external module ${confname}")
+  # The module macros rely on the presence of a CONFIG_NODEMCU_CMODULE_XXX
+  # def, so we have to add it explicitly as it won't be coming from Kconfig
+  target_compile_options(${COMPONENT_LIB} PRIVATE "-DCONFIG_NODEMCU_CMODULE_${confname}")
+  target_link_libraries(${COMPONENT_LIB} "-u ${confname}_module_selected1")
+endfunction()

extcomp-template/CMakeLists.txt

@@ -1,37 +1,20 @@
-# Modify this list as necessary to include all your source files.
-set(extmod_srcs
-  "mymod.c"
-)
-
-# If necessary, add items to the PRIV_REQUIRES list below
+# Update source files and includes as necessary
 idf_component_register(
-  SRCS ${extmod_srcs}
-  INCLUDE_DIRS "." "${CMAKE_CURRENT_BINARY_DIR}"
+  SRCS
+    "mymod.c"
+  PRIV_INCLUDE_DIRS
+    "${CMAKE_CURRENT_BINARY_DIR}"
   PRIV_REQUIRES
     "base_nodemcu"
     "lua"
     "platform"
 )
 
-# The remainder is boiler-plate glue to get the linker to actually include
-# the modules enabled in Kconfig. No user-serviceable parts inside.
-
-# Match up all the extmod source files with their corresponding Kconfig
-# option in the form NODEMCU_CMODULE_<modname> and if enabled, add a
-# "-u <modname>_module_selected1" option to force the linker to include
-# the module. See components/core/include/module.h for further details on
-# how this works.
-set(extmods_enabled)
-foreach(extmod_src ${extmod_srcs})
-  string(REPLACE ".c" "" module_name ${extmod_src})
-  string(TOUPPER ${module_name} module_ucase)
-  set(mod_opt "CONFIG_NODEMCU_CMODULE_${module_ucase}")
-  if (${${mod_opt}})
-    list(APPEND extmods_enabled ${module_ucase})
-  endif()
-endforeach()
-message("Including the following modules: ${extmods_enabled}")
-
-foreach(mod ${extmods_enabled})
-  target_link_libraries(${COMPONENT_LIB} "-u ${mod}_module_selected1")
-endforeach()
+# To register the module with NodeMCU, use one of the below functions.
+# The name given MUST match the first argument to the NODEMCU_MODULE() in
+# the module's C file.
+#
+# For modules with a Kconfig option, use:
+extmod_register_conditional(MYMOD)
+# ...and for modules without a Kconfig option, instead use:
+#extmod_register_unconditional(MYMOD)

extcomp-template/Kconfig

@@ -1,13 +1,8 @@
-menu "External modules"
-
 config NODEMCU_CMODULE_MYMOD
-        bool "Mymod module"
+    bool "External NodeMCU module: mymod"
     default "y"
     help
         Includes the mymod module. This module is only an example for
         showing how to use external modules. Note that the config option
-            name has to be prefixed with NODEMCU_CMODULE_ and the suffix
-            has to match the first argument in the NODEMCU_MODULE() macro
-            in the .c file.
-
-endmenu
+        name has to be prefixed with NODEMCU_CMODULE_ and the module
+        registered with extmod_register_conditional(MYMOD) in CMakeLists.txt