Error when blt_add_code_checks calls blt_add_yapf_target

[chapman39]

Having this issue in LiDO where when I call blt_add_code_checks I get the following error:

CMake Error at cmake/blt/cmake/SetupCodeChecks.cmake:873 (message):
  blt_add_yapf_target requires a SRC_FILES parameter
Call Stack (most recent call first):
  cmake/blt/cmake/SetupCodeChecks.cmake:246 (blt_add_yapf_target)
  CMakeLists.txt:187 (blt_add_code_checks)

The SRC_FILES variable is set to _py_sources (retrieved from blt_split_source_list_by_language, see https://github.com/LLNL/blt/blob/develop/cmake/SetupCodeChecks.cmake#L156).

I guess when blt_split_source_list_by_language is called, Python_LIST is empty, which means _py_sources is empty, which means SRC_FILES is "" when it gets down to blt_add_yapf_target.

When I commented out the fatal error I was able to make by LiDO build without issues. Maybe this check is not required?

[white238]

I see two solutions:

1. Have the user required to not provide a YAPF config file if you don't provide Python files to add code checks for (this seems less than robust).

2. Check on each of these if blocks that you are actually providing source files to run checks for:
   

   blt/cmake/SetupCodeChecks.cmake

   Lines 238 to 255 in 92450b0

   	if (YAPF_FOUND AND DEFINED arg_YAPF_CFG_FILE)
   	set(_check_target_name ${arg_PREFIX}_yapf_check)
   	blt_error_if_target_exists(${_check_target_name} ${_error_msg})
   	set(_style_target_name ${arg_PREFIX}_yapf_style)
   	blt_error_if_target_exists(${_style_target_name} ${_error_msg})
   	blt_add_yapf_target( NAME ${_check_target_name}
   	MODIFY_FILES FALSE
   	CFG_FILE ${arg_YAPF_CFG_FILE}
   	WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
   	SRC_FILES ${_py_sources} )
   	blt_add_yapf_target( NAME ${_style_target_name}
   	MODIFY_FILES TRUE
   	CFG_FILE ${arg_YAPF_CFG_FILE}
   	WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
   	SRC_FILES ${_py_sources} )
   	endif()

I would lean towards the second option.