cmake: refactor quick check given component dirs

tools/cmake/build.cmake

@@ -147,9 +147,8 @@ function(__build_init idf_path)
     file(GLOB component_dirs ${idf_path}/components/*)
     foreach(component_dir ${component_dirs})
         get_filename_component(component_dir ${component_dir} ABSOLUTE)
-        get_filename_component(base_dir ${component_dir} NAME)
-        string(SUBSTRING "${base_dir}" 0 1 first_char)
-        if(NOT first_char STREQUAL ".")
+        __component_dir_quick_check(is_component ${component_dir})
+        if(is_component)
             __component_add(${component_dir} ${prefix})
         endif()
     endforeach()

tools/cmake/component.cmake

@@ -95,6 +95,36 @@ macro(__component_set_properties)
     __component_set_property(${component_target} REQUIRED_IDF_TARGETS "${__REQUIRED_IDF_TARGETS}")
 endmacro()
 
+#
+# Perform a quick check if given component dir satisfies basic requirements.
+#
+function(__component_dir_quick_check var component_dir)
+    set(res 1)
+    get_filename_component(abs_dir ${component_dir} ABSOLUTE)
+
+    # Check this is really a directory and that a CMakeLists.txt file for this component exists
+    # - warn and skip anything which isn't valid looking (probably cruft)
+    if(NOT IS_DIRECTORY "${abs_dir}")
+        message(STATUS "Unexpected file in components directory: ${abs_dir}")
+        set(res 0)
+    endif()
+
+    get_filename_component(base_dir ${abs_dir} NAME)
+    string(SUBSTRING "${base_dir}" 0 1 first_char)
+
+    if(NOT first_char STREQUAL ".")
+        if(NOT EXISTS "${abs_dir}/CMakeLists.txt")
+            message(STATUS "Component directory ${abs_dir} does not contain a CMakeLists.txt file. "
+                "No component will be added")
+            set(res 0)
+        endif()
+    else()
+        set(res 0) # quietly ignore dot-folders
+    endif()
+
+    set(${var} ${res} PARENT_SCOPE)
+endfunction()
+
 #
 # Add a component to process in the build. The components are keeped tracked of in property
 # __COMPONENT_TARGETS in component target form.
@@ -112,16 +142,8 @@ function(__component_add component_dir prefix)
     get_filename_component(abs_dir ${component_dir} ABSOLUTE)
     get_filename_component(base_dir ${abs_dir} NAME)
 
-    # Check this is really a directory and that a CMakeLists.txt file for this component exists
-    # - warn and skip anything which isn't valid looking (probably cruft)
-    if(NOT IS_DIRECTORY "${abs_dir}")
-        message(WARNING "Unexpected file in components directory: ${abs_dir}")
-        return()
-    endif()
     if(NOT EXISTS "${abs_dir}/CMakeLists.txt")
-        message(WARNING "Component directory ${abs_dir} does not contain a CMakeLists.txt file. "
-            "No component will be added")
-        return()
+        message(FATAL_ERROR "Directory '${component_dir}' does not contain a component.")
     endif()
 
     set(component_name ${base_dir})

tools/cmake/project.cmake

@@ -149,8 +149,8 @@ function(__project_init components_var test_components_var)
             foreach(component_dir ${component_dirs})
                 if(EXISTS ${component_dir}/CMakeLists.txt)
                     get_filename_component(base_dir ${component_dir} NAME)
-                    string(SUBSTRING "${base_dir}" 0 1 first_char)
-                    if(NOT first_char STREQUAL ".")
+                    __component_dir_quick_check(is_component ${component_dir})
+                    if(is_component)
                         idf_build_component(${component_dir})
                     endif()
                 endif()