getdeps: add an add_fb_python_unittest() function

Summary:
Add a function for defining Python unit tests.  This creates the test
executable, and also emits logic to perform test discovery for ctest.

Reviewed By: simpkins

Differential Revision: D17610034

fbshipit-source-id: cdf15b0b04acc1d3e906a1e2a95eb327951176ba

build/fbcode_builder/CMake/FBPythonTestAddTests.cmake

@@ -0,0 +1,59 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+# Add a command to be emitted to the CTest file
+set(ctest_script)
+function(add_command CMD)
+  set(escaped_args "")
+  foreach(arg ${ARGN})
+    # Escape all arguments using "Bracket Argument" syntax
+    # We could skip this for argument that don't contain any special
+    # characters if we wanted to make the output slightly more human-friendly.
+    set(escaped_args "${escaped_args} [==[${arg}]==]")
+  endforeach()
+  set(ctest_script "${ctest_script}${CMD}(${escaped_args})\n" PARENT_SCOPE)
+endfunction()
+
+if(NOT EXISTS "${TEST_EXECUTABLE}")
+  message(FATAL_ERROR "Test executable does not exist: ${TEST_EXECUTABLE}")
+endif()
+execute_process(
+  COMMAND ${CMAKE_COMMAND} -E env ${TEST_ENV} "${TEST_INTERPRETER}" "${TEST_EXECUTABLE}" --list-tests
+  WORKING_DIRECTORY "${TEST_WORKING_DIR}"
+  OUTPUT_VARIABLE output
+  RESULT_VARIABLE result
+)
+if(NOT "${result}" EQUAL 0)
+  string(REPLACE "\n" "\n  " output "${output}")
+  message(
+    FATAL_ERROR
+    "Error running test executable: ${TEST_EXECUTABLE}\n"
+    "Output:\n"
+    "  ${output}\n"
+  )
+endif()
+
+# Parse output
+string(REPLACE "\n" ";" tests_list "${output}")
+foreach(test_name ${tests_list})
+  add_command(
+    add_test
+    "${TEST_PREFIX}${test_name}"
+    ${CMAKE_COMMAND} -E env ${TEST_ENV}
+    "${TEST_INTERPRETER}" "${TEST_EXECUTABLE}" "${test_name}"
+  )
+  add_command(
+    set_tests_properties
+    "${TEST_PREFIX}${test_name}"
+    PROPERTIES
+    WORKING_DIRECTORY "${TEST_WORKING_DIR}"
+    ${TEST_PROPERTIES}
+  )
+endforeach()
+
+# Set a list of discovered tests in the parent scope, in case users
+# want access to this list as a CMake variable
+if(TEST_LIST)
+  add_command(set ${TEST_LIST} ${tests_list})
+endif()
+
+file(WRITE "${CTEST_FILE}" "${ctest_script}")