From d6d344d8330a5975fc102e8f275d47044294f1d1 Mon Sep 17 00:00:00 2001 From: Eric Appelt Date: Mon, 17 Apr 2017 13:35:43 -0500 Subject: [PATCH] bpo-29514: Check magic number for bugfix release (#54) * bpo-29514: Check magic number for micro release Add a dict importlib.util.EXPECTED_MAGIC_NUMBERS which details the initial and expected pyc magic number for each minor release. This gives a mechanism for users to check if the magic number has changed within a release and for a test to ensure procedure is followed if a change is necessary. Add a test to check the current MAGIC_NUMBER against the expected number for the release if the current release is at candidate or final level. On test failure, describe to the developer the procedure for changing the magic number. * Simplify magic number release test Simplify the magic number release test by removing EXPECTED_MAGIC_NUMBERS table and making the expected magic number self-contained within the test. BPO: 29514 * Improve magic number test execution and message Improve the execution of the magic number test by using skipUnless for alpha and beta releases, and directly inheriting from unittest.TestCase rather than using the machinery for the other tests. Also improve the error message to explain the reason for caution in changing the magic number. BPO: 29514 --- Lib/test/test_importlib/test_util.py | 44 ++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/Lib/test/test_importlib/test_util.py b/Lib/test/test_importlib/test_util.py index d615375b342..ac18e5c34b8 100644 --- a/Lib/test/test_importlib/test_util.py +++ b/Lib/test/test_importlib/test_util.py @@ -4,6 +4,7 @@ init = util.import_importlib('importlib') machinery = util.import_importlib('importlib.machinery') importlib_util = util.import_importlib('importlib.util') +import importlib.util import os import pathlib import string @@ -757,5 +758,48 @@ class PEP3147Tests: ) = util.test_both(PEP3147Tests, util=importlib_util) +class MagicNumberTests(unittest.TestCase): + """ + Test release compatibility issues relating to importlib + """ + @unittest.skipUnless( + sys.version_info.releaselevel in ('final', 'release'), + 'only applies to candidate or final python release levels' + ) + def test_magic_number(self): + """ + Each python minor release should generally have a MAGIC_NUMBER + that does not change once the release reaches candidate status. + + Once a release reaches candidate status, the value of the constant + EXPECTED_MAGIC_NUMBER in this test should be changed. + This test will then check that the actual MAGIC_NUMBER matches + the expected value for the release. + + In exceptional cases, it may be required to change the MAGIC_NUMBER + for a maintenance release. In this case the change should be + discussed in python-dev. If a change is required, community + stakeholders such as OS package maintainers must be notified + in advance. Such exceptional releases will then require an + adjustment to this test case. + """ + EXPECTED_MAGIC_NUMBER = 3379 + actual = int.from_bytes(importlib.util.MAGIC_NUMBER[:2], 'little') + + msg = ( + "To avoid breaking backwards compatibility with cached bytecode " + "files that can't be automatically regenerated by the current " + "user, candidate and final releases require the current " + "importlib.util.MAGIC_NUMBER to match the expected " + "magic number in this test. Set the expected " + "magic number in this test to the current MAGIC_NUMBER to " + "continue with the release.\n\n" + "Changing the MAGIC_NUMBER for a maintenance release " + "requires discussion in python-dev and notification of " + "community stakeholders." + ) + self.assertEqual(EXPECTED_MAGIC_NUMBER, actual, msg) + + if __name__ == '__main__': unittest.main()