CMAKE_MINIMUM_REQUIRED(VERSION 3.2)
PROJECT(Example)

INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})

FIND_PACKAGE(PythonLibs REQUIRED)
INCLUDE_DIRECTORIES(${PYTHON_INCLUDE_DIRS})

FIND_PACKAGE(SWIG REQUIRED)
INCLUDE(${SWIG_USE_FILE})

# Should pull it from the file, but doesn't
SET(I_FILE example.i)
# With a full path, the module name is successfully pulled from the file
#SET(I_FILE "${CMAKE_CURRENT_SOURCE_DIR}/example.i")
# Setting the property works too
#SET_PROPERTY(SOURCE ${I_FILE} PROPERTY SWIG_MODULE_NAME example_swig)

SWIG_ADD_MODULE(Example_wrap python ${I_FILE})