Merge branch 'bugfix/override_cmake_python' into 'master'

cmake: Minor Python CMake build fixes

Closes IDFGH-4454

See merge request espressif/esp-idf!12975

tools/cmake/build.cmake

@@ -130,9 +130,11 @@ function(__build_init idf_path)
     # Must be global so as to be accessible from any subdirectory in custom projects.
     add_library(__idf_build_target STATIC IMPORTED GLOBAL)
 
-    set_default(python "python")
+    # Set the Python path (which may be passed in via -DPYTHON=) and store in a build property
+    set_default(PYTHON "python")
+    file(TO_CMAKE_PATH ${PYTHON} PYTHON)
+    idf_build_set_property(PYTHON ${PYTHON})
 
-    idf_build_set_property(PYTHON ${python})
     idf_build_set_property(IDF_PATH ${idf_path})
 
     idf_build_set_property(__PREFIX idf)
@@ -273,8 +275,12 @@ function(__build_check_python)
         message(STATUS "Checking Python dependencies...")
         execute_process(COMMAND "${python}" "${idf_path}/tools/check_python_dependencies.py"
             RESULT_VARIABLE result)
-        if(NOT result EQUAL 0)
+        if(result EQUAL 1)
+            # check_python_dependencies returns error code 1 on failure
             message(FATAL_ERROR "Some Python dependencies must be installed. Check above message for details.")
+        elseif(NOT result EQUAL 0)
+            # means check_python_dependencies.py failed to run at all, result should be an error message
+            message(FATAL_ERROR "Failed to run Python dependency check. Python: ${python}, Error: ${result}")
         endif()
     endif()
 endfunction()

tools/cmake/project.cmake

@@ -6,12 +6,15 @@ cmake_minimum_required(VERSION 3.5)
 # call.
 include(${CMAKE_CURRENT_LIST_DIR}/idf.cmake)
 
+# setting PYTHON variable here for compatibility only, new code should use
+# idf_build_get_property(variable PYTHON)
+idf_build_get_property(PYTHON PYTHON)
+if(NOT PYTHON)
+    message(FATAL_ERROR "Internal error, PYTHON build property not set correctly.")
+endif()
+
+# legacy variable for compatibility
 set(IDFTOOL ${PYTHON} "${IDF_PATH}/tools/idf.py")
-# Internally, the Python interpreter is already set to 'python'. Re-set here
-# to be absolutely sure.
-set_default(PYTHON "python")
-file(TO_CMAKE_PATH ${PYTHON} PYTHON)
-idf_build_set_property(PYTHON ${PYTHON})
 
 # On processing, checking Python required modules can be turned off if it was
 # already checked externally.