absltest: do not fail tests on Python 3.12+ when no tests ran AND:

- Either test filtering is used
- Sharding is used and the shard index > 0, i.e. only the first shard will fail when no tests ran on Python 3.12+.

Context: Python 3.12 unittest will now fail when no tests ran after the change from python/cpython#102051. Since `absltest` is built on top of `unittest`, it will follow this behavior change in Python 3.12.

However, when test filtering is used in `absltest`, often used via `bazel test --test_filter=<my_filter>`, the current user expectation is the `bazel test` command should NOT fail is at least one test ran. Since the test runner here has no visibility of the overall `bazel` invocation, we'll make the test not fail when test filtering is used via bazel's environment variable. This is the existing behavior before Python 3.12.

Also test absl-py on Python 3.12.

PiperOrigin-RevId: 565190992

.github/workflows/test.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
         os: [ubuntu-latest, macOS-latest, windows-latest]
 
     steps:
@@ -30,6 +30,7 @@ jobs:
         id: setup_python
         with:
           python-version: ${{ matrix.python-version }}
+          allow-prereleases: true
 
       - name: Install virtualenv
         run: |

CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com).
 
 *   `absl-py` no longer supports Python 3.6. It has reached end-of-life for more
     than a year now.
+*   Support Python 3.12.
 *   (logging) `logging.exception` can now take `exc_info` as argument, with
     default value `True`. Prior to this change setting `exc_info` would raise
     `KeyError`, this change fixes this behaviour.

absl/testing/BUILD

@@ -163,12 +163,16 @@ py_test(
     name = "tests/absltest_sharding_test",
     size = "small",
     srcs = ["tests/absltest_sharding_test.py"],
-    data = [":tests/absltest_sharding_test_helper"],
+    data = [
+        ":tests/absltest_sharding_test_helper",
+        ":tests/absltest_sharding_test_helper_no_tests",
+    ],
     python_version = "PY3",
     srcs_version = "PY3",
     deps = [
         ":_bazelize_command",
         ":absltest",
+        ":parameterized",
         ":tests/absltest_env",
     ],
 )
@@ -182,6 +186,13 @@ py_binary(
     deps = [":absltest"],
 )
 
+py_binary(
+    name = "tests/absltest_sharding_test_helper_no_tests",
+    testonly = 1,
+    srcs = ["tests/absltest_sharding_test_helper_no_tests.py"],
+    deps = [":absltest"],
+)
+
 py_test(
     name = "tests/absltest_test",
     size = "small",

absl/testing/absltest.py

@@ -2317,8 +2317,7 @@ def get_default_xml_output_filename():
         os.path.splitext(os.path.basename(sys.argv[0]))[0] + '.xml')
 
 
-def _setup_filtering(argv):
-  # type: (MutableSequence[Text]) -> None
+def _setup_filtering(argv: MutableSequence[str]) -> bool:
   """Implements the bazel test filtering protocol.
 
   The following environment variable is used in this method:
@@ -2333,16 +2332,20 @@ def _setup_filtering(argv):
 
   Args:
     argv: the argv to mutate in-place.
+
+  Returns:
+    Whether test filtering is requested.
   """
   test_filter = os.environ.get('TESTBRIDGE_TEST_ONLY')
   if argv is None or not test_filter:
-    return
+    return False
 
   filters = shlex.split(test_filter)
   if sys.version_info[:2] >= (3, 7):
     filters = ['-k=' + test_filter for test_filter in filters]
 
   argv[1:1] = filters
+  return True
 
 
 def _setup_test_runner_fail_fast(argv):
@@ -2369,8 +2372,9 @@ def _setup_test_runner_fail_fast(argv):
   argv[1:1] = ['--failfast']
 
 
-def _setup_sharding(custom_loader=None):
-  # type: (Optional[unittest.TestLoader]) -> unittest.TestLoader
+def _setup_sharding(
+    custom_loader: Optional[unittest.TestLoader] = None,
+) -> Tuple[unittest.TestLoader, Optional[int]]:
   """Implements the bazel sharding protocol.
 
   The following environment variables are used in this method:
@@ -2389,8 +2393,10 @@ def _setup_sharding(custom_loader=None):
     custom_loader: A TestLoader to be made sharded.
 
   Returns:
-    The test loader for shard-filtering or the standard test loader, depending
-    on the sharding environment variables.
+    A tuple of ``(test_loader, shard_index)``. ``test_loader`` is for
+    shard-filtering or the standard test loader depending on the sharding
+    environment variables. ``shard_index`` is the shard index, or ``None`` when
+    sharding is not used.
   """
 
   # It may be useful to write the shard file even if the other sharding
@@ -2408,7 +2414,7 @@ def _setup_sharding(custom_loader=None):
   base_loader = custom_loader or TestLoader()
   if 'TEST_TOTAL_SHARDS' not in os.environ:
     # Not using sharding, use the expected test loader.
-    return base_loader
+    return base_loader, None
 
   total_shards = int(os.environ['TEST_TOTAL_SHARDS'])
   shard_index = int(os.environ['TEST_SHARD_INDEX'])
@@ -2437,25 +2443,70 @@ def getShardedTestCaseNames(testCaseClass):
     return [x for x in ordered_names if x in filtered_names]
 
   base_loader.getTestCaseNames = getShardedTestCaseNames
-  return base_loader
+  return base_loader, shard_index
+
+
+def _run_and_get_tests_result(
+    argv: MutableSequence[str],
+    args: Sequence[Any],
+    kwargs: MutableMapping[str, Any],
+    xml_test_runner_class: Type[unittest.TextTestRunner],
+) -> Tuple[unittest.TestResult, bool]:
+  """Same as run_tests, but it doesn't exit.
 
+  Args:
+    argv: sys.argv with the command-line flags removed from the front, i.e. the
+      argv with which :func:`app.run()<absl.app.run>` has called
+      ``__main__.main``. It is passed to
+      ``unittest.TestProgram.__init__(argv=)``, which does its own flag parsing.
+      It is ignored if kwargs contains an argv entry.
+    args: Positional arguments passed through to
+      ``unittest.TestProgram.__init__``.
+    kwargs: Keyword arguments passed through to
+      ``unittest.TestProgram.__init__``.
+    xml_test_runner_class: The type of the test runner class.
 
-# pylint: disable=line-too-long
-def _run_and_get_tests_result(argv, args, kwargs, xml_test_runner_class):
-  # type: (MutableSequence[Text], Sequence[Any], MutableMapping[Text, Any], Type) -> unittest.TestResult
-  # pylint: enable=line-too-long
-  """Same as run_tests, except it returns the result instead of exiting."""
+  Returns:
+    A tuple of ``(test_result, fail_when_no_tests_ran)``.
+    ``fail_when_no_tests_ran`` indicates whether the test should fail when
+    no tests ran.
+  """
 
   # The entry from kwargs overrides argv.
   argv = kwargs.pop('argv', argv)
 
+  if sys.version_info[:2] >= (3, 12):
+    # Python 3.12 unittest changed the behavior from PASS to FAIL in
+    # https://github.com/python/cpython/pull/102051. absltest follows this.
+    fail_when_no_tests_ran = True
+  else:
+    # Historically, absltest and unittest before Python 3.12 passes if no tests
+    # ran.
+    fail_when_no_tests_ran = False
+
   # Set up test filtering if requested in environment.
-  _setup_filtering(argv)
+  if _setup_filtering(argv):
+    # When test filtering is requested, ideally we also want to fail when no
+    # tests ran. However, the test filters are usually done when running bazel.
+    # When you run multiple targets, e.g. `bazel test //my_dir/...
+    # --test_filter=MyTest`, you don't necessarily want individual tests to fail
+    # because no tests match in that particular target.
+    # Due to this use case, we don't fail when test filtering is requested via
+    # the environment variable from bazel.
+    fail_when_no_tests_ran = False
+
   # Set up --failfast as requested in environment
   _setup_test_runner_fail_fast(argv)
 
   # Shard the (default or custom) loader if sharding is turned on.
-  kwargs['testLoader'] = _setup_sharding(kwargs.get('testLoader', None))
+  kwargs['testLoader'], shard_index = _setup_sharding(
+      kwargs.get('testLoader', None)
+  )
+  if shard_index is not None and shard_index > 0:
+    # When sharding is requested, all the shards except the first one shall not
+    # fail when no tests ran. This happens when the shard count is greater than
+    # the test case count.
+    fail_when_no_tests_ran = False
 
   # XML file name is based upon (sorted by priority):
   # --xml_output_file flag, XML_OUTPUT_FILE variable,
@@ -2533,9 +2584,13 @@ def _run_and_get_tests_result(argv, args, kwargs, xml_test_runner_class):
   # on argv, which is sys.argv without the command-line flags.
   kwargs['argv'] = argv
 
+  # Request unittest.TestProgram to not exit. The exit will be handled by
+  # `absltest.run_tests`.
+  kwargs['exit'] = False
+
   try:
     test_program = unittest.TestProgram(*args, **kwargs)
-    return test_program.result
+    return test_program.result, fail_when_no_tests_ran
   finally:
     if xml_buffer:
       try:
@@ -2545,9 +2600,11 @@ def _run_and_get_tests_result(argv, args, kwargs, xml_test_runner_class):
         xml_buffer.close()
 
 
-def run_tests(argv, args, kwargs):  # pylint: disable=line-too-long
-  # type: (MutableSequence[Text], Sequence[Any], MutableMapping[Text, Any]) -> None
-  # pylint: enable=line-too-long
+def run_tests(
+    argv: MutableSequence[Text],
+    args: Sequence[Any],
+    kwargs: MutableMapping[Text, Any],
+) -> None:
   """Executes a set of Python unit tests.
 
   Most users should call absltest.main() instead of run_tests.
@@ -2568,8 +2625,11 @@ def run_tests(argv, args, kwargs):  # pylint: disable=line-too-long
     kwargs: Keyword arguments passed through to
       ``unittest.TestProgram.__init__``.
   """
-  result = _run_and_get_tests_result(
-      argv, args, kwargs, xml_reporter.TextAndXMLTestRunner)
+  result, fail_when_no_tests_ran = _run_and_get_tests_result(
+      argv, args, kwargs, xml_reporter.TextAndXMLTestRunner
+  )
+  if fail_when_no_tests_ran and result.testsRun == 0:
+    sys.exit(5)
   sys.exit(not result.wasSuccessful())
 
 

absl/testing/tests/absltest_filtering_test.py

@@ -156,7 +156,12 @@ def test_not_found_filters_py36(self, use_env_variable, use_app_run):
   def test_not_found_filters_py37(self, use_env_variable, use_app_run):
     out, exit_code = self._run_filtered('NotExistedClass.not_existed_method',
                                         use_env_variable, use_app_run)
-    self.assertEqual(0, exit_code)
+    if not use_env_variable and sys.version_info[:2] >= (3, 12):
+      # When test filter is requested with the unittest `-k` flag, absltest
+      # respect unittest to fail when no tests run on Python 3.12+.
+      self.assertEqual(5, exit_code)
+    else:
+      self.assertEqual(0, exit_code)
     self.assertIn('Ran 0 tests', out)
 
   @absltest.skipIf(

absl/testing/tests/absltest_sharding_test.py

@@ -16,45 +16,50 @@
 
 import os
 import subprocess
+import sys
 
 from absl.testing import _bazelize_command
 from absl.testing import absltest
+from absl.testing import parameterized
 from absl.testing.tests import absltest_env
 
 
 NUM_TEST_METHODS = 8  # Hard-coded, based on absltest_sharding_test_helper.py
 
 
-class TestShardingTest(absltest.TestCase):
+class TestShardingTest(parameterized.TestCase):
   """Integration tests: Runs a test binary with sharding.
 
   This is done by setting the sharding environment variables.
   """
 
   def setUp(self):
     super().setUp()
-    self._test_name = 'absl/testing/tests/absltest_sharding_test_helper'
     self._shard_file = None
 
   def tearDown(self):
     super().tearDown()
     if self._shard_file is not None and os.path.exists(self._shard_file):
       os.unlink(self._shard_file)
 
-  def _run_sharded(self,
-                   total_shards,
-                   shard_index,
-                   shard_file=None,
-                   additional_env=None):
+  def _run_sharded(
+      self,
+      total_shards,
+      shard_index,
+      shard_file=None,
+      additional_env=None,
+      helper_name='absltest_sharding_test_helper',
+  ):
     """Runs the py_test binary in a subprocess.
 
     Args:
       total_shards: int, the total number of shards.
       shard_index: int, the shard index.
-      shard_file: string, if not 'None', the path to the shard file.
-        This method asserts it is properly created.
+      shard_file: string, if not 'None', the path to the shard file. This method
+        asserts it is properly created.
       additional_env: Additional environment variables to be set for the py_test
         binary.
+      helper_name: The name of the helper binary.
 
     Returns:
       (stdout, exit_code) tuple of (string, int).
@@ -72,12 +77,14 @@ def _run_sharded(self,
       if os.path.exists(shard_file):
         os.unlink(shard_file)
 
+    helper = 'absl/testing/tests/' + helper_name
     proc = subprocess.Popen(
-        args=[_bazelize_command.get_executable_path(self._test_name)],
+        args=[_bazelize_command.get_executable_path(helper)],
         env=env,
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
-        universal_newlines=True)
+        universal_newlines=True,
+    )
     stdout = proc.communicate()[0]
 
     if shard_file:
@@ -140,7 +147,11 @@ def test_with_one_shard(self):
     self._assert_sharding_correctness(1)
 
   def test_with_ten_shards(self):
-    self._assert_sharding_correctness(10)
+    shards = 10
+    # This test relies on the shard count to be greater than the number of
+    # tests.
+    self.assertGreater(NUM_TEST_METHODS, shards)
+    self._assert_sharding_correctness(shards)
 
   def test_sharding_with_randomization(self):
     # If we're both sharding *and* randomizing, we need to confirm that we
@@ -156,6 +167,32 @@ def test_sharding_with_randomization(self):
     self.assertEqual(set(first_tests), set(second_tests))
     self.assertNotEqual(first_tests, second_tests)
 
+  @parameterized.named_parameters(
+      ('total_1_index_0', 1, 0, None),
+      ('total_2_index_0', 2, 0, None),
+      # The 2nd shard (index=1) should not fail.
+      ('total_2_index_1', 2, 1, 0),
+  )
+  def test_no_tests_ran(
+      self, total_shards, shard_index, override_expected_exit_code
+  ):
+    if override_expected_exit_code is not None:
+      expected_exit_code = override_expected_exit_code
+    elif sys.version_info[:2] >= (3, 12):
+      expected_exit_code = 5
+    else:
+      expected_exit_code = 0
+    out, exit_code = self._run_sharded(
+        total_shards,
+        shard_index,
+        helper_name='absltest_sharding_test_helper_no_tests',
+    )
+    self.assertEqual(
+        expected_exit_code,
+        exit_code,
+        'Unexpected exit code, output:\n{}'.format(out),
+    )
+
 
 if __name__ == '__main__':
   absltest.main()