bpo-34945: Buffer output in test suite only when creating junit file (GH-10204)

pablogsal · web-flow · commit 02277482ea76 · 2018-10-29T16:09:41.000-04:00
After commit d0f49d2, the output of the test suite is always buffered as the test output needs to be included in the JUnit file in same cases (as when a test fails). This has the consequence that printing or using debuggers (like pdb) in the test suite does not result in a good user experience anymore. This commit modifies the test suite runner so it only captures the test output when the JUnit file is requested to fix the regression so prints and debuggers are usable again.
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
@@ -1921,10 +1921,9 @@ def _filter_suite(suite, pred):
 
 def _run_suite(suite):
     """Run tests from a unittest.TestSuite-derived class."""
-    runner = get_test_runner(sys.stdout, verbosity=verbose)
-
-    # TODO: Remove this before merging (here for easy comparison with old impl)
-    #runner = unittest.TextTestRunner(sys.stdout, verbosity=2, failfast=failfast)
+    runner = get_test_runner(sys.stdout,
+                             verbosity=verbose,
+                             capture_output=(junit_xml_list is not None))
 
     result = runner.run(suite)
 
diff --git a/Lib/test/support/testresult.py b/Lib/test/support/testresult.py
@@ -60,10 +60,12 @@ def _add_result(self, test, capture=False, **args):
             e.set('time', f'{time.perf_counter() - self.__start_time:0.6f}')
 
         if capture:
-            stdout = self._stdout_buffer.getvalue().rstrip()
-            ET.SubElement(e, 'system-out').text = stdout
-            stderr = self._stderr_buffer.getvalue().rstrip()
-            ET.SubElement(e, 'system-err').text = stderr
+            if self._stdout_buffer is not None:
+                stdout = self._stdout_buffer.getvalue().rstrip()
+                ET.SubElement(e, 'system-out').text = stdout
+            if self._stderr_buffer is not None:
+                stderr = self._stderr_buffer.getvalue().rstrip()
+                ET.SubElement(e, 'system-err').text = stderr
 
         for k, v in args.items():
             if not k or not v:
@@ -152,23 +154,24 @@ def get_xml_element(self):
         return e
 
 class QuietRegressionTestRunner:
-    def __init__(self, stream):
+    def __init__(self, stream, buffer=False):
         self.result = RegressionTestResult(stream, None, 0)
+        self.result.buffer = buffer
 
     def run(self, test):
         test(self.result)
         return self.result
 
-def get_test_runner_class(verbosity):
+def get_test_runner_class(verbosity, buffer=False):
     if verbosity:
         return functools.partial(unittest.TextTestRunner,
                                  resultclass=RegressionTestResult,
-                                 buffer=True,
+                                 buffer=buffer,
                                  verbosity=verbosity)
-    return QuietRegressionTestRunner
+    return functools.partial(QuietRegressionTestRunner, buffer=buffer)
 
-def get_test_runner(stream, verbosity):
-    return get_test_runner_class(verbosity)(stream)
+def get_test_runner(stream, verbosity, capture_output=False):
+    return get_test_runner_class(verbosity, capture_output)(stream)
 
 if __name__ == '__main__':
     class TestTests(unittest.TestCase):
