gh-128067: Fix pyrepl overriding printed output without newlines

[JanEricNitschke]

I tried a bit to debug this and narrowed it down to these two lines for windows and unix terminals respectively:

• https://github.com/python/cpython/blob/main/Lib/_pyrepl/windows_console.py#L186-L187
• https://github.com/python/cpython/blob/main/Lib/_pyrepl/unix_console.py#L238-L239

Because while properly running the repl in unix doesnt cause the issue, running the test i added also fails there before these changes.

I am not 100% sure if this is the base and 100% correct way, but it causes the test to pass on unix and fixes the issue on windows for me.

I also attempted to try to be able to run these tests for windows (because thats where we actually saw the issue) but didnt manage unfortunately.

With the fix in the unix console:

 python -m coverage run --pylib --branch --source=pyrepl Lib/test/regrtest.py  test_pyrepl -m test_no_newline
Using random seed: 4126788206
0:00:00 load avg: 0.17 Run 1 test sequentially in a single process
0:00:00 load avg: 0.17 [1/1] test_pyrepl
0:00:04 load avg: 0.17 [1/1] test_pyrepl passed

== Tests result: SUCCESS ==

1 test OK.

Total duration: 4.7 sec
Total tests: run=1 (filtered)
Total test files: run=1/1 (filtered)
Result: SUCCESS

Without:

 python -m coverage run --pylib --branch --source=pyrepl Lib/test/regrtest.py  test_pyrepl -m test_no_newline
Using random seed: 3832564122
0:00:00 load avg: 0.30 Run 1 test sequentially in a single process
0:00:00 load avg: 0.30 [1/1] test_pyrepl
test test_pyrepl failed -- Traceback (most recent call last):
  File "/mnt/d/Programming/Projects/cpython/Lib/test/support/__init__.py", line 2923, in wrapper
    return func(*args, **kwargs)
  File "/mnt/d/Programming/Projects/cpython/Lib/test/test_pyrepl/test_pyrepl.py", line 1819, in test_no_newline
    self.assertIn(expected_output_sequence, cleaned_output)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'Something pretty long>>> exit()' not found in 'print(\'Something pretty long\', end=\'\')\r\nexit()\r\nPython 3.15.0a0 (heads/main:c919d02ede, Sep  6 2025, 15:55:27) [GCC 13.3.0] on linux\r\nType "help", "copyright", "credits" or "license" for more information.\r\n\x1b[1A\n>>> print(\'Something pretty long\', end=\'\')\x1b[42D\n\rSomething pretty long\x1b[1A\n>>> exit()\x1b[10D\n\r'

0:00:02 load avg: 0.30 [1/1/1] test_pyrepl failed (1 failure)

== Tests result: FAILURE ==

1 test failed:
    test_pyrepl

Total duration: 2.0 sec
Total tests: run=1 (filtered) failures=1
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

• Issue: [Windows] Python 3.13 New REPL prompt swallows characters with print(..., end=" ") #128067

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.