bpo-38991: Remove test.support.strip_python_stderr() (GH-17490)

test.support: run_python_until_end(), assert_python_ok() and
assert_python_failure() functions no longer strip whitespaces from
stderr.

Author: vstinner

Doc/library/test.rst

@@ -686,13 +686,6 @@ The :mod:`test.support` module defines the following functions:
    ``sys.stdout`` if it's not set.
 
 
-.. function:: strip_python_strerr(stderr)
-
-   Strip the *stderr* of a Python process from potential debug output
-   emitted by the interpreter.  This will typically be run on the result of
-   :meth:`subprocess.Popen.communicate`.
-
-
 .. function:: args_from_interpreter_flags()
 
    Return a list of command line arguments reproducing the current settings
@@ -1499,6 +1492,9 @@ script execution tests.
    in a subprocess.  The values can include ``__isolated``, ``__cleanenv``,
    ``__cwd``, and ``TERM``.
 
+   .. versionchanged:: 3.9
+      The function no longer strips whitespaces from *stderr*.
+
 
 .. function:: assert_python_ok(*args, **env_vars)
 
@@ -1512,6 +1508,9 @@ script execution tests.
    Python is started in isolated mode (command line option ``-I``),
    except if the ``__isolated`` keyword is set to ``False``.
 
+   .. versionchanged:: 3.9
+      The function no longer strips whitespaces from *stderr*.
+
 
 .. function:: assert_python_failure(*args, **env_vars)
 
@@ -1521,6 +1520,9 @@ script execution tests.
 
    See :func:`assert_python_ok` for more options.
 
+   .. versionchanged:: 3.9
+      The function no longer strips whitespaces from *stderr*.
+
 
 .. function:: spawn_python(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw)
 

Lib/test/support/__init__.py

@@ -2512,16 +2512,6 @@ def swap_item(obj, item, new_val):
             if item in obj:
                 del obj[item]
 
-def strip_python_stderr(stderr):
-    """Strip the stderr of a Python process from potential debug output
-    emitted by the interpreter.
-
-    This will typically be run on the result of the communicate() method
-    of a subprocess.Popen object.
-    """
-    stderr = re.sub(br"\[\d+ refs, \d+ blocks\]\r?\n?", b"", stderr).strip()
-    return stderr
-
 requires_type_collecting = unittest.skipIf(hasattr(sys, 'getcounts'),
                         'types are immortal if COUNT_ALLOCS is defined')
 

Lib/test/support/script_helper.py

@@ -11,7 +11,7 @@
 import zipfile
 
 from importlib.util import source_from_cache
-from test.support import make_legacy_pyc, strip_python_stderr
+from test.support import make_legacy_pyc
 
 
 # Cached result of the expensive test performed in the function below.
@@ -134,7 +134,6 @@ def run_python_until_end(*args, **env_vars):
             proc.kill()
             subprocess._cleanup()
     rc = proc.returncode
-    err = strip_python_stderr(err)
     return _PythonRunResult(rc, out, err), cmd_line
 
 def _assert_python(expected_success, /, *args, **env_vars):

Lib/test/test_cmd_line.py

@@ -332,10 +332,10 @@ def test_output_newline(self):
 
         if sys.platform == 'win32':
             self.assertEqual(b'1\r\n2\r\n', out)
-            self.assertEqual(b'3\r\n4', err)
+            self.assertEqual(b'3\r\n4\r\n', err)
         else:
             self.assertEqual(b'1\n2\n', out)
-            self.assertEqual(b'3\n4', err)
+            self.assertEqual(b'3\n4\n', err)
 
     def test_unmached_quote(self):
         # Issue #10206: python program starting with unmatched quote
@@ -391,7 +391,7 @@ def preexec():
             stderr=subprocess.PIPE,
             preexec_fn=preexec)
         out, err = p.communicate()
-        self.assertEqual(support.strip_python_stderr(err), b'')
+        self.assertEqual(err, b'')
         self.assertEqual(p.returncode, 42)
 
     def test_no_stdin(self):

Lib/test/test_cmd_line_script.py

@@ -535,7 +535,7 @@ def test_pep_409_verbiage(self):
             script_name = _make_test_script(script_dir, 'script', script)
             exitcode, stdout, stderr = assert_python_failure(script_name)
             text = stderr.decode('ascii').split('\n')
-            self.assertEqual(len(text), 4)
+            self.assertEqual(len(text), 5)
             self.assertTrue(text[0].startswith('Traceback'))
             self.assertTrue(text[1].startswith('  File '))
             self.assertTrue(text[3].startswith('NameError'))
@@ -579,7 +579,7 @@ def test_issue20500_exit_with_exception_value(self):
             script_name = _make_test_script(script_dir, 'script', script)
             exitcode, stdout, stderr = assert_python_failure(script_name)
             text = stderr.decode('ascii')
-            self.assertEqual(text, "some text")
+            self.assertEqual(text.rstrip(), "some text")
 
     def test_syntaxerror_unindented_caret_position(self):
         script = "1 + 1 = 2\n"

Lib/test/test_faulthandler.py

@@ -71,9 +71,8 @@ def get_output(self, code, filename=None, fd=None):
         with support.SuppressCrashReport():
             process = script_helper.spawn_python('-c', code, pass_fds=pass_fds)
             with process:
-                stdout, stderr = process.communicate()
+                output, stderr = process.communicate()
                 exitcode = process.wait()
-        output = support.strip_python_stderr(stdout)
         output = output.decode('ascii', 'backslashreplace')
         if filename:
             self.assertEqual(output, '')

Lib/test/test_gc.py

@@ -1,7 +1,7 @@
 import unittest
 import unittest.mock
 from test.support import (verbose, refcount_test, run_unittest,
-                          strip_python_stderr, cpython_only, start_threads,
+                          cpython_only, start_threads,
                           temp_dir, requires_type_collecting, TESTFN, unlink,
                           import_module)
 from test.support.script_helper import assert_python_ok, make_script
@@ -671,8 +671,8 @@ def run_command(code):
             p.stdout.close()
             p.stderr.close()
             self.assertEqual(p.returncode, 0)
-            self.assertEqual(stdout.strip(), b"")
-            return strip_python_stderr(stderr)
+            self.assertEqual(stdout, b"")
+            return stderr
 
         stderr = run_command(code % "0")
         self.assertIn(b"ResourceWarning: gc: 2 uncollectable objects at "

Lib/test/test_subprocess.py

@@ -85,15 +85,6 @@ def tearDown(self):
         self.doCleanups()
         support.reap_children()
 
-    def assertStderrEqual(self, stderr, expected, msg=None):
-        # In a debug build, stuff like "[6580 refs]" is printed to stderr at
-        # shutdown time.  That frustrates tests trying to check stderr produced
-        # from a spawned Python process.
-        actual = support.strip_python_stderr(stderr)
-        # strip_python_stderr also strips whitespace, so we do too.
-        expected = expected.strip()
-        self.assertEqual(actual, expected, msg)
-
 
 class PopenTestException(Exception):
     pass
@@ -547,7 +538,7 @@ def test_stderr_pipe(self):
                           'import sys; sys.stderr.write("strawberry")'],
                          stderr=subprocess.PIPE)
         with p:
-            self.assertStderrEqual(p.stderr.read(), b"strawberry")
+            self.assertEqual(p.stderr.read(), b"strawberry")
 
     def test_stderr_filedes(self):
         # stderr is set to open file descriptor
@@ -559,7 +550,7 @@ def test_stderr_filedes(self):
                          stderr=d)
         p.wait()
         os.lseek(d, 0, 0)
-        self.assertStderrEqual(os.read(d, 1024), b"strawberry")
+        self.assertEqual(os.read(d, 1024), b"strawberry")
 
     def test_stderr_fileobj(self):
         # stderr is set to open file object
@@ -570,7 +561,7 @@ def test_stderr_fileobj(self):
                          stderr=tf)
         p.wait()
         tf.seek(0)
-        self.assertStderrEqual(tf.read(), b"strawberry")
+        self.assertEqual(tf.read(), b"strawberry")
 
     def test_stderr_redirect_with_no_stdout_redirect(self):
         # test stderr=STDOUT while stdout=None (not set)
@@ -589,8 +580,8 @@ def test_stderr_redirect_with_no_stdout_redirect(self):
                              stderr=subprocess.PIPE)
         stdout, stderr = p.communicate()
         #NOTE: stdout should get stderr from grandchild
-        self.assertStderrEqual(stdout, b'42')
-        self.assertStderrEqual(stderr, b'') # should be empty
+        self.assertEqual(stdout, b'42')
+        self.assertEqual(stderr, b'') # should be empty
         self.assertEqual(p.returncode, 0)
 
     def test_stdout_stderr_pipe(self):
@@ -603,7 +594,7 @@ def test_stdout_stderr_pipe(self):
                              stdout=subprocess.PIPE,
                              stderr=subprocess.STDOUT)
         with p:
-            self.assertStderrEqual(p.stdout.read(), b"appleorange")
+            self.assertEqual(p.stdout.read(), b"appleorange")
 
     def test_stdout_stderr_file(self):
         # capture stdout and stderr to the same open file
@@ -618,7 +609,7 @@ def test_stdout_stderr_file(self):
                              stderr=tf)
         p.wait()
         tf.seek(0)
-        self.assertStderrEqual(tf.read(), b"appleorange")
+        self.assertEqual(tf.read(), b"appleorange")
 
     def test_stdout_filedes_of_stdout(self):
         # stdout is set to 1 (#1531862).
@@ -767,7 +758,7 @@ def test_communicate_stderr(self):
                              stderr=subprocess.PIPE)
         (stdout, stderr) = p.communicate()
         self.assertEqual(stdout, None)
-        self.assertStderrEqual(stderr, b"pineapple")
+        self.assertEqual(stderr, b"pineapple")
 
     def test_communicate(self):
         p = subprocess.Popen([sys.executable, "-c",
@@ -782,7 +773,7 @@ def test_communicate(self):
         self.addCleanup(p.stdin.close)
         (stdout, stderr) = p.communicate(b"banana")
         self.assertEqual(stdout, b"banana")
-        self.assertStderrEqual(stderr, b"pineapple")
+        self.assertEqual(stderr, b"pineapple")
 
     def test_communicate_timeout(self):
         p = subprocess.Popen([sys.executable, "-c",
@@ -801,7 +792,7 @@ def test_communicate_timeout(self):
         # after it completes.
         (stdout, stderr) = p.communicate()
         self.assertEqual(stdout, "banana")
-        self.assertStderrEqual(stderr.encode(), b"pineapple\npear\n")
+        self.assertEqual(stderr.encode(), b"pineapple\npear\n")
 
     def test_communicate_timeout_large_output(self):
         # Test an expiring timeout while the child is outputting lots of data.
@@ -887,7 +878,7 @@ def test_writes_before_communicate(self):
         p.stdin.write(b"banana")
         (stdout, stderr) = p.communicate(b"split")
         self.assertEqual(stdout, b"bananasplit")
-        self.assertStderrEqual(stderr, b"")
+        self.assertEqual(stderr, b"")
 
     def test_universal_newlines_and_text(self):
         args = [
@@ -1005,7 +996,6 @@ def test_universal_newlines_communicate_stdin_stdout_stderr(self):
         self.assertEqual("line1\nline2\nline3\nline4\nline5\n", stdout)
         # Python debug build push something like "[42442 refs]\n"
         # to stderr at exit of subprocess.
-        # Don't use assertStderrEqual because it strips CR and LF from output.
         self.assertTrue(stderr.startswith("eline2\neline6\neline7\n"))
 
     def test_universal_newlines_communicate_encodings(self):
@@ -2240,13 +2230,13 @@ def test_send_signal(self):
     def test_kill(self):
         p = self._kill_process('kill')
         _, stderr = p.communicate()
-        self.assertStderrEqual(stderr, b'')
+        self.assertEqual(stderr, b'')
         self.assertEqual(p.wait(), -signal.SIGKILL)
 
     def test_terminate(self):
         p = self._kill_process('terminate')
         _, stderr = p.communicate()
-        self.assertStderrEqual(stderr, b'')
+        self.assertEqual(stderr, b'')
         self.assertEqual(p.wait(), -signal.SIGTERM)
 
     def test_send_signal_dead(self):
@@ -2294,8 +2284,8 @@ def check_close_std_fds(self, fds):
                        stdin=stdin,
                        stdout=subprocess.PIPE,
                        stderr=subprocess.PIPE).communicate()
-            err = support.strip_python_stderr(err)
-            self.assertEqual((out, err), (b'apple', b'orange'))
+            self.assertEqual(out, b'apple')
+            self.assertEqual(err, b'orange')
         finally:
             self._restore_fds(saved_fds)
 
@@ -2380,7 +2370,7 @@ def test_remapping_std_fds(self):
                 os.lseek(fd, 0, 0)
 
             out = os.read(temp_fds[2], 1024)
-            err = support.strip_python_stderr(os.read(temp_fds[0], 1024))
+            err = os.read(temp_fds[0], 1024).strip()
             self.assertEqual(out, b"got STDIN")
             self.assertEqual(err, b"err")
 
@@ -2422,7 +2412,7 @@ def check_swap_fds(self, stdin_no, stdout_no, stderr_no):
                     os.lseek(fd, 0, 0)
 
                 out = os.read(stdout_no, 1024)
-                err = support.strip_python_stderr(os.read(stderr_no, 1024))
+                err = os.read(stderr_no, 1024).strip()
             finally:
                 self._restore_fds(saved_fds)
 
@@ -3338,7 +3328,7 @@ def _kill_process(self, method, *args):
             p.stdout.read(1)
             getattr(p, method)(*args)
             _, stderr = p.communicate()
-            self.assertStderrEqual(stderr, b'')
+            self.assertEqual(stderr, b'')
             returncode = p.wait()
         self.assertNotEqual(returncode, 0)
 
@@ -3361,7 +3351,7 @@ def _kill_dead_process(self, method, *args):
             # This shouldn't raise even though the child is now dead
             getattr(p, method)(*args)
             _, stderr = p.communicate()
-            self.assertStderrEqual(stderr, b'')
+            self.assertEqual(stderr, b'')
             rc = p.wait()
         self.assertEqual(rc, 42)
 
@@ -3550,7 +3540,7 @@ def test_pipe(self):
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE) as proc:
             self.assertEqual(proc.stdout.read(), b"stdout")
-            self.assertStderrEqual(proc.stderr.read(), b"stderr")
+            self.assertEqual(proc.stderr.read(), b"stderr")
 
         self.assertTrue(proc.stdout.closed)
         self.assertTrue(proc.stderr.closed)

Lib/test/test_support.py

@@ -653,7 +653,6 @@ def test_fd_count(self):
     # run_doctest
     # threading_cleanup
     # reap_threads
-    # strip_python_stderr
     # can_symlink
     # skip_unless_symlink
     # SuppressCrashReport

Lib/test/test_warnings/__init__.py

@@ -1219,7 +1219,8 @@ def __del__(self):
 a=A()
         """
         rc, out, err = assert_python_ok("-c", code)
-        self.assertEqual(err.decode(), '<string>:7: UserWarning: test')
+        self.assertEqual(err.decode().rstrip(),
+                         '<string>:7: UserWarning: test')
 
     def test_late_resource_warning(self):
         # Issue #21925: Emitting a ResourceWarning late during the Python

Misc/NEWS.d/next/Tests/2019-12-07-00-52-09.bpo-38991.JE3_o-.rst

@@ -0,0 +1,5 @@
+:mod:`test.support`: :func:`~test.support.run_python_until_end`,
+:func:`~test.support.assert_python_ok` and
+:func:`~test.support.assert_python_failure` functions no longer strip
+whitespaces from stderr. Remove ``test.support.strip_python_stderr()``
+function.