From ab84c73244fd3c599c2ac86c7eee58b6a9cdacea Mon Sep 17 00:00:00 2001
From: Renz Christian Bagaporo <renz@espressif.com>
Date: Mon, 13 Jan 2020 14:46:11 +0800
Subject: [PATCH] cmake: add subdirectory if exists utility

---
 tools/cmake/utilities.cmake | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/cmake/utilities.cmake b/tools/cmake/utilities.cmake
index 88a5b0912..fa0abc030 100644
--- a/tools/cmake/utilities.cmake
+++ b/tools/cmake/utilities.cmake
@@ -302,4 +302,17 @@ function(file_generate output)
 
     set_property(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
         APPEND PROPERTY ADDITIONAL_MAKE_CLEAN_FILES "${output}")
+endfunction()
+
+# add_subdirectory_if_exists
+#
+# Like add_subdirectory, but only proceeds if the given source directory exists.
+function(add_subdirectory_if_exists source_dir)
+    get_filename_component(abs_dir "${source_dir}"
+        ABSOLUTE BASE_DIR "${CMAKE_CURRENT_LIST_DIR}")
+    if(EXISTS "${abs_dir}")
+        add_subdirectory("${source_dir}" ${ARGN})
+    else()
+        message(STATUS "Subdirectory '${abs_dir}' does not exist, skipped.")
+    endif()
 endfunction()
\ No newline at end of file