regrtest computes statistics (#108793)

test_netrc, test_pep646_syntax and test_xml_etree now return results
in the test_main() function.

Changes:

* Rewrite TestResult as a dataclass with a new State class.
* Add test.support.TestStats class and Regrtest.stats_dict attribute.
* libregrtest.runtest functions now modify a TestResult instance
  in-place.
* libregrtest summary lists the number of run tests and skipped
  tests, and denied resources.
* Add TestResult.has_meaningful_duration() method.
* Compute TestResult duration in the upper function.
* Use time.perf_counter() instead of time.monotonic().
* Regrtest: rename 'resource_denieds' attribute to 'resource_denied'.
* Rename CHILD_ERROR to MULTIPROCESSING_ERROR.
* Use match/case syntadx to have different code depending on the
  test state.

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Lib/test/support/__init__.py

@@ -4,6 +4,7 @@ if __name__ != 'test.support':
     raise ImportError('support must be imported from the test package')
 
 import contextlib
+import dataclasses
 import functools
 import getpass
 import _opcode
@@ -118,18 +119,21 @@ class Error(Exception):
 
 class TestFailed(Error):
     """Test failed."""
-
-class TestFailedWithDetails(TestFailed):
-    """Test failed."""
-    def __init__(self, msg, errors, failures):
+    def __init__(self, msg, *args, stats=None):
         self.msg = msg
-        self.errors = errors
-        self.failures = failures
-        super().__init__(msg, errors, failures)
+        self.stats = stats
+        super().__init__(msg, *args)
 
     def __str__(self):
         return self.msg
 
+class TestFailedWithDetails(TestFailed):
+    """Test failed."""
+    def __init__(self, msg, errors, failures, stats):
+        self.errors = errors
+        self.failures = failures
+        super().__init__(msg, errors, failures, stats=stats)
+
 class TestDidNotRun(Error):
     """Test did not run any subtests."""
 
@@ -1105,6 +1109,30 @@ def _filter_suite(suite, pred):
                 newtests.append(test)
     suite._tests = newtests
 
+@dataclasses.dataclass(slots=True)
+class TestStats:
+    tests_run: int = 0
+    failures: int = 0
+    skipped: int = 0
+
+    @staticmethod
+    def from_unittest(result):
+        return TestStats(result.testsRun,
+                         len(result.failures),
+                         len(result.skipped))
+
+    @staticmethod
+    def from_doctest(results):
+        return TestStats(results.attempted,
+                         results.failed,
+                         results.skipped)
+
+    def accumulate(self, stats):
+        self.tests_run += stats.tests_run
+        self.failures += stats.failures
+        self.skipped += stats.skipped
+
+
 def _run_suite(suite):
     """Run tests from a unittest.TestSuite-derived class."""
     runner = get_test_runner(sys.stdout,
@@ -1119,6 +1147,7 @@ def _run_suite(suite):
     if not result.testsRun and not result.skipped and not result.errors:
         raise TestDidNotRun
     if not result.wasSuccessful():
+        stats = TestStats.from_unittest(result)
         if len(result.errors) == 1 and not result.failures:
             err = result.errors[0][1]
         elif len(result.failures) == 1 and not result.errors:
@@ -1128,7 +1157,8 @@ def _run_suite(suite):
             if not verbose: err += "; run in verbose mode for details"
         errors = [(str(tc), exc_str) for tc, exc_str in result.errors]
         failures = [(str(tc), exc_str) for tc, exc_str in result.failures]
-        raise TestFailedWithDetails(err, errors, failures)
+        raise TestFailedWithDetails(err, errors, failures, stats=stats)
+    return result
 
 
 # By default, don't filter tests
@@ -1237,7 +1267,7 @@ def run_unittest(*classes):
         else:
             suite.addTest(loader.loadTestsFromTestCase(cls))
     _filter_suite(suite, match_test)
-    _run_suite(suite)
+    return _run_suite(suite)
 
 #=======================================================================
 # Check for the presence of docstrings.
@@ -1277,13 +1307,18 @@ def run_doctest(module, verbosity=None, optionflags=0):
     else:
         verbosity = None
 
-    f, t = doctest.testmod(module, verbose=verbosity, optionflags=optionflags)
-    if f:
-        raise TestFailed("%d of %d doctests failed" % (f, t))
+    results = doctest.testmod(module,
+                             verbose=verbosity,
+                             optionflags=optionflags)
+    if results.failed:
+        stats = TestStats.from_doctest(results)
+        raise TestFailed(f"{results.failed} of {results.attempted} "
+                         f"doctests failed",
+                         stats=stats)
     if verbose:
         print('doctest (%s) ... %d tests with zero failures' %
-              (module.__name__, t))
-    return f, t
+              (module.__name__, results.attempted))
+    return results
 
 
 #=======================================================================