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})

159c159
<     "${infile}")
---
>     "${swig_source_file_fullname}")

diff --git a/Modules/UseSWIG.cmake b/Modules/UseSWIG.cmake
index 7423418..1862876 100644
--- a/Modules/UseSWIG.cmake
+++ b/Modules/UseSWIG.cmake
@@ -156,7 +156,7 @@ macro(SWIG_ADD_SOURCE_TO_MODULE name outfiles infile)
   SWIG_GET_EXTRA_OUTPUT_FILES(${SWIG_MODULE_${name}_LANGUAGE}
     swig_extra_generated_files
     "${swig_outdir}"
-    "${infile}")
+    "${swig_source_file_fullname}")
   set(swig_generated_file_fullname
     "${swig_outdir}/${swig_source_file_name_we}")
   # add the language into the name of the file (i.e. TCL_wrap)