CatchAddTests.cmake: Refactor into callable method

Move test discovery logic into new catch_discover_tests_impl method
and make CatchAddTests aware of whether it is being launched in
CMake's script mode.

When launched in script mode, catch_discover_tests_impl is called
passing arguments obtained from the definitions passed into the call
to cmake. This preserves the existing behavior assumed by Catch.cmake.

Looking ahead, it also allows CatchAddTests to be included in
generated files and call catch_discover_tests_impl to perform test
discovery at test runtime with the new PRE_TEST discovery mode
introduced later.

extras/CatchAddTests.cmake

@@ -1,28 +1,6 @@
 # Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
 # file Copyright.txt or https://cmake.org/licensing for details.
 
-set(prefix "${TEST_PREFIX}")
-set(suffix "${TEST_SUFFIX}")
-set(spec ${TEST_SPEC})
-set(extra_args ${TEST_EXTRA_ARGS})
-set(properties ${TEST_PROPERTIES})
-set(reporter ${TEST_REPORTER})
-set(output_dir ${TEST_OUTPUT_DIR})
-set(output_prefix ${TEST_OUTPUT_PREFIX})
-set(output_suffix ${TEST_OUTPUT_SUFFIX})
-set(dl_paths ${TEST_DL_PATHS})
-set(script)
-set(suite)
-set(tests)
-
-if(WIN32)
-  set(dl_paths_variable_name PATH)
-elseif(APPLE)
-  set(dl_paths_variable_name DYLD_LIBRARY_PATH)
-else()
-  set(dl_paths_variable_name LD_LIBRARY_PATH)
-endif()
-
 function(add_command NAME)
   set(_args "")
   # use ARGV* instead of ARGN, because ARGN splits arrays into multiple arguments
@@ -38,10 +16,42 @@ function(add_command NAME)
   set(script "${script}${NAME}(${_args})\n" PARENT_SCOPE)
 endfunction()
 
+function(catch_discover_tests_impl)
+
+  cmake_parse_arguments(
+    ""
+    ""
+    "TEST_EXECUTABLE;TEST_WORKING_DIR;TEST_DL_PATHS;TEST_OUTPUT_DIR;TEST_OUTPUT_PREFIX;TEST_OUTPUT_SUFFIX;TEST_PREFIX;TEST_REPORTER;TEST_SPEC;TEST_SUFFIX;TEST_LIST;CTEST_FILE"
+    "TEST_EXTRA_ARGS;TEST_PROPERTIES;TEST_EXECUTOR"
+    ${ARGN}
+  )
+
+  set(prefix "${_TEST_PREFIX}")
+  set(suffix "${_TEST_SUFFIX}")
+  set(spec ${_TEST_SPEC})
+  set(extra_args ${_TEST_EXTRA_ARGS})
+  set(properties ${_TEST_PROPERTIES})
+  set(reporter ${_TEST_REPORTER})
+  set(output_dir ${_TEST_OUTPUT_DIR})
+  set(output_prefix ${_TEST_OUTPUT_PREFIX})
+  set(output_suffix ${_TEST_OUTPUT_SUFFIX})
+  set(dl_paths ${_TEST_DL_PATHS})
+  set(script)
+  set(suite)
+  set(tests)
+
+  if(WIN32)
+    set(dl_paths_variable_name PATH)
+  elseif(APPLE)
+    set(dl_paths_variable_name DYLD_LIBRARY_PATH)
+  else()
+    set(dl_paths_variable_name LD_LIBRARY_PATH)
+  endif()
+
   # Run test executable to get list of available tests
-if(NOT EXISTS "${TEST_EXECUTABLE}")
+  if(NOT EXISTS "${_TEST_EXECUTABLE}")
     message(FATAL_ERROR
-    "Specified test executable '${TEST_EXECUTABLE}' does not exist"
+      "Specified test executable '${_TEST_EXECUTABLE}' does not exist"
     )
   endif()
 
@@ -51,14 +61,14 @@ if(dl_paths)
   endif()
 
   execute_process(
-  COMMAND ${TEST_EXECUTOR} "${TEST_EXECUTABLE}" ${spec} --list-tests --verbosity quiet
+    COMMAND ${_TEST_EXECUTOR} "${_TEST_EXECUTABLE}" ${spec} --list-tests --verbosity quiet
     OUTPUT_VARIABLE output
     RESULT_VARIABLE result
-  WORKING_DIRECTORY "${TEST_WORKING_DIR}"
+    WORKING_DIRECTORY "${_TEST_WORKING_DIR}"
   )
   if(NOT ${result} EQUAL 0)
     message(FATAL_ERROR
-    "Error running test executable '${TEST_EXECUTABLE}':\n"
+      "Error running test executable '${_TEST_EXECUTABLE}':\n"
       "  Result: ${result}\n"
       "  Output: ${output}\n"
     )
@@ -94,7 +104,7 @@ endif()
 
   # Prepare output dir
   if(output_dir AND NOT IS_ABSOLUTE ${output_dir})
-  set(output_dir "${TEST_WORKING_DIR}/${output_dir}")
+    set(output_dir "${_TEST_WORKING_DIR}/${output_dir}")
     if(NOT EXISTS ${output_dir})
       file(MAKE_DIRECTORY ${output_dir})
     endif()
@@ -124,8 +134,8 @@ foreach(line ${output})
     # ...and add to script
     add_command(add_test
       "${prefix}${test}${suffix}"
-    ${TEST_EXECUTOR}
+      ${_TEST_EXECUTOR}
-    "${TEST_EXECUTABLE}"
+      "${_TEST_EXECUTABLE}"
       "${test_name}"
       ${extra_args}
       "${reporter_arg}"
@@ -134,7 +144,7 @@ foreach(line ${output})
     add_command(set_tests_properties
       "${prefix}${test}${suffix}"
       PROPERTIES
-    WORKING_DIRECTORY "${TEST_WORKING_DIR}"
+      WORKING_DIRECTORY "${_TEST_WORKING_DIR}"
       ${properties}
     )
 
@@ -150,7 +160,28 @@ endforeach()
 
   # Create a list of all discovered tests, which users may use to e.g. set
   # properties on the tests
-add_command(set ${TEST_LIST} ${tests})
+  add_command(set ${_TEST_LIST} ${tests})
 
   # Write CTest script
-file(WRITE "${CTEST_FILE}" "${script}")
+  file(WRITE "${_CTEST_FILE}" "${script}")
+endfunction()
+
+if(CMAKE_SCRIPT_MODE_FILE)
+  catch_discover_tests_impl(
+    TEST_EXECUTABLE ${TEST_EXECUTABLE}
+    TEST_EXECUTOR ${TEST_EXECUTOR}
+    TEST_WORKING_DIR ${TEST_WORKING_DIR}
+    TEST_SPEC ${TEST_SPEC}
+    TEST_EXTRA_ARGS ${TEST_EXTRA_ARGS}
+    TEST_PROPERTIES ${TEST_PROPERTIES}
+    TEST_PREFIX ${TEST_PREFIX}
+    TEST_SUFFIX ${TEST_SUFFIX}
+    TEST_LIST ${TEST_LIST}
+    TEST_REPORTER ${TEST_REPORTER}
+    TEST_OUTPUT_DIR ${TEST_OUTPUT_DIR}
+    TEST_OUTPUT_PREFIX ${TEST_OUTPUT_PREFIX}
+    TEST_OUTPUT_SUFFIX ${TEST_OUTPUT_SUFFIX}
+    TEST_DL_PATHS ${TEST_DL_PATHS}
+    CTEST_FILE ${CTEST_FILE}
+  )
+endif()