Cmake: add defconfig preprocess capability in Cmake build environment(recursively expand #include)

Add:
    cmake/nuttx_process_config.cmake
    tools/process_config.py

    Update nuttx/CMakeLists.txt to call process_config defined ini
    nuttx_process_config.cmake to process defconfig before actually using it

CMakeLists.txt

@@ -158,6 +158,22 @@ if(NOT EXISTS "${NUTTX_DEFCONFIG}")
   message(FATAL_ERROR "No config file found at ${NUTTX_DEFCONFIG}")
 endif()
 
+# Process initial defconfig ###################################################
+# Process initial defconfig to recursively expand #include in it
+
+include(nuttx_process_config)
+get_filename_component(NUTTX_DEFCONFIG_DIR "${NUTTX_DEFCONFIG}" DIRECTORY)
+process_config(
+  ${CMAKE_BINARY_DIR}/.defconfig.processed
+  ${NUTTX_DEFCONFIG}
+  INCLUDE_PATHS
+  ${NUTTX_DEFCONFIG_DIR}/../../common/configs
+  ${NUTTX_DEFCONFIG_DIR}/../common
+  ${NUTTX_DEFCONFIG_DIR}
+  ${NUTTX_DIR}/../apps
+  ${NUTTX_DIR}/../nuttx-apps)
+set(NUTTX_DEFCONFIG ${CMAKE_BINARY_DIR}/.defconfig.processed)
+
 # Generate initial .config ###################################################
 # This is needed right before any other configure step so that we can source
 # Kconfig variables into CMake variables

cmake/nuttx_process_config.cmake

@@ -0,0 +1,48 @@
+# ##############################################################################
+# cmake/nuttx_process_config.cmake
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more contributor
+# license agreements.  See the NOTICE file distributed with this work for
+# additional information regarding copyright ownership.  The ASF licenses this
+# file to you under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+#
+# ##############################################################################
+
+function(process_config OUTPUT INPUT)
+  set(options)
+  set(oneValueArgs)
+  set(multiValueArgs INCLUDE_PATHS)
+  cmake_parse_arguments(PARSE_ARGV 2 PROCESS_INCLUDES "${options}"
+                        "${oneValueArgs}" "${multiValueArgs}")
+
+  find_package(Python3 REQUIRED COMPONENTS Interpreter)
+
+  set(include_args "")
+  foreach(path IN LISTS PROCESS_INCLUDES_INCLUDE_PATHS)
+    list(APPEND include_args "${path}")
+  endforeach()
+
+  message(STATUS "Processing includes: ${INPUT} → ${OUTPUT}")
+  execute_process(
+    COMMAND ${Python3_EXECUTABLE} ${CMAKE_SOURCE_DIR}/tools/process_config.py
+            ${OUTPUT} ${INPUT} ${include_args}
+    RESULT_VARIABLE result
+    OUTPUT_VARIABLE out
+    ERROR_VARIABLE err)
+
+  if(NOT result EQUAL 0)
+    message(FATAL_ERROR "Failed to process includes:\n${err}")
+  endif()
+endfunction()

tools/process_config.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+# tools/process_config.py
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+
+import re
+import sys
+from pathlib import Path
+
+
+def expand_file(input_path, include_paths, processed=None):
+    """
+    Recursively expand the file, returning its contents in order as a list of lines.
+    """
+    if processed is None:
+        processed = set()
+
+    input_path = Path(input_path).resolve()
+    if input_path in processed:
+        return []  # Already processed, avoid duplicate includes
+    processed.add(input_path)
+
+    expanded_lines = []
+
+    with input_path.open("r", encoding="utf-8") as f:
+        lines = f.readlines()
+
+    for line in lines:
+        line_strip = line.strip()
+        match = re.match(r'#include\s*[<"]([^">]+)[">]', line_strip)
+        if match:
+            include_file = match.group(1)
+            found = False
+
+            # Check the current directory first
+
+            direct_path = input_path.parent / include_file
+            if direct_path.exists():
+                expanded_lines.extend(
+                    expand_file(direct_path, include_paths, processed)
+                )
+                found = True
+            else:
+                # Then check in the include paths
+
+                for path in include_paths:
+                    candidate = Path(path) / include_file
+                    if candidate.exists():
+                        expanded_lines.extend(
+                            expand_file(candidate, include_paths, processed)
+                        )
+                        found = True
+                        break
+
+            if not found:
+                print(
+                    f'ERROR: Cannot find "{include_file}" from {input_path}',
+                    file=sys.stderr,
+                )
+                sys.exit(1)
+        else:
+            expanded_lines.append(line)
+
+    expanded_lines.append("\n")  # Keep separation between files
+    return expanded_lines
+
+
+def process_file(output_path, input_path, include_paths):
+    lines = expand_file(input_path, include_paths)
+    with open(output_path, "w", encoding="utf-8") as out:
+        out.writelines(lines)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 3:
+        print(
+            "Usage: process_includes.py <output_file> <input_file> [include_paths...]",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+    output_file = Path(sys.argv[1])
+    input_file = sys.argv[2]
+    include_dirs = sys.argv[3:]
+
+    if output_file.exists():
+        output_file.unlink()
+
+    process_file(output_file, input_file, include_dirs)