Add readline workaround for libedit

We had a very similar workaround before for pyreadline, which had a similar
issue:

- Introduced in pytest-dev#1281
- Removed in pytest-dev#8848 for pytest-dev#8733 and pytest-dev#8847

This technically will regress the issues above, but those issues just mean that
`import readline` is broken in general, so the user should fix it instead (by
e.g. uninstalling pyreadline).

Fixes pytest-dev#12888
Fixes pytest-dev#13170

changelog/12888.bugfix.rst

@@ -0,0 +1 @@
+Fixed broken input when using Python 3.13+ and a ``libedit`` build of Python, such as on macOS or with uv-managed Python binaries from the ``python-build-standalone`` project. This could manifest e.g. by a broken prompt when using ``Pdb``, or seeing empty inputs with manual usage of ``input()`` and suspended capturing.

src/_pytest/capture.py

@@ -80,6 +80,20 @@ def _colorama_workaround() -> None:
             pass
 
 
+def _readline_workaround() -> None:
+    """Ensure readline is imported early so it attaches to the correct stdio handles.
+
+    This isn't a problem with the default GNU readline implementation, but in
+    some configurations, Python uses libedit instead (on macOS, and for prebuilt
+    binaries such as used by uv).
+
+    In theory this is only needed if readline.backend == "libedit", but the
+    workaround consists of importing readline here, so we already worked around
+    the issue by the time we could check if we need to.
+    """
+    import readline  # noqa: F401
+
+
 def _windowsconsoleio_workaround(stream: TextIO) -> None:
     """Workaround for Windows Unicode console handling.
 
@@ -141,6 +155,7 @@ def pytest_load_initial_conftests(early_config: Config) -> Generator[None]:
     if ns.capture == "fd":
         _windowsconsoleio_workaround(sys.stdout)
     _colorama_workaround()
+    _readline_workaround()
     pluginmanager = early_config.pluginmanager
     capman = CaptureManager(ns.capture)
     pluginmanager.register(capman, "capturemanager")

testing/test_capture.py

@@ -3,6 +3,7 @@
 
 from collections.abc import Generator
 import contextlib
+import re
 import io
 from io import UnsupportedOperation
 import os
@@ -1666,3 +1667,32 @@ def test_logging():
     )
     result.stdout.no_fnmatch_line("*Captured stderr call*")
     result.stdout.no_fnmatch_line("*during collection*")
+
+
+def test_libedit_workaround(pytester: Pytester) -> None:
+    pytester.makeconftest("""
+    import pytest
+
+
+    def pytest_terminal_summary(config):
+        capture = config.pluginmanager.getplugin("capturemanager")
+        capture.suspend_global_capture(in_=True)
+
+        print("Enter 'hi'")
+        value = input()
+        print(f"value: {value!r}")
+
+        capture.resume_global_capture()
+    """)
+    import readline
+    backend = getattr(readline, "backend", readline.__doc__)  # added in Python 3.13
+    print(f"Readline backend: {backend}")
+
+    child = pytester.spawn_pytest("")
+    child.expect(r"Enter 'hi'")
+    child.sendline("hi")
+    rest = child.read().decode("utf8")
+    print(rest)
+    match = re.search(r"^value: '(.*)'\r?$", rest, re.MULTILINE)
+    assert match is not None
+    assert match.group(1) == "hi"