Fix readline backspace/line-wrapping on linux

CHANGES.rst

@@ -29,6 +29,10 @@ Unreleased
     non-shadowed help option names, so ``Try '... -h'`` no longer points to a
     subcommand option that shadows ``-h``. All surviving names are shown
     (``-h/--help``). :issue:`2790` :pr:`3208`
+-   Fix readline functionality on non-Windows platforms. Prompt text is now
+    passed directly to readline instead of being printed separately, allowing
+    proper backspace, line editing, and line wrapping behavior. :issue:`2968`
+    :pr:`2969`
 
 Version 8.3.3
 -------------

src/click/termui.py

@@ -7,10 +7,12 @@
 import sys
 import typing as t
 from contextlib import AbstractContextManager
+from contextlib import redirect_stdout
 from gettext import gettext as _
 
 from ._compat import isatty
 from ._compat import strip_ansi
+from ._compat import WIN
 from .exceptions import Abort
 from .exceptions import UsageError
 from .globals import resolve_color_default
@@ -57,6 +59,26 @@ def hidden_prompt_func(prompt: str) -> str:
     return getpass.getpass(prompt)
 
 
+def _readline_prompt(func: t.Callable[[str], str], text: str, err: bool) -> str:
+    """Call a prompt function, passing the full prompt on non-Windows so
+    readline can handle line editing and cursor positioning correctly.
+
+    On Windows the prompt is written separately via :func:`echo` for
+    colorama support, with only the last character passed to *func*.
+    """
+    if WIN:
+        # Write the prompt separately so that we get nice coloring
+        # through colorama on Windows.
+        echo(text[:-1], nl=False, err=err)
+        # Echo the last character to stdout to work around an issue
+        # where readline causes backspace to clear the whole line.
+        return func(text[-1:])
+    if err:
+        with redirect_stdout(sys.stderr):
+            return func(text)
+    return func(text)
+
+
 def _build_prompt(
     text: str,
     suffix: str,
@@ -147,12 +169,7 @@ def prompt(
     def prompt_func(text: str) -> str:
         f = hidden_prompt_func if hide_input else visible_prompt_func
         try:
-            # Write the prompt separately so that we get nice
-            # coloring through colorama on Windows
-            echo(text[:-1], nl=False, err=err)
-            # Echo the last character to stdout to work around an issue where
-            # readline causes backspace to clear the whole line.
-            return f(text[-1:])
+            return _readline_prompt(f, text, err)
         except (KeyboardInterrupt, EOFError):
             # getpass doesn't print a newline if the user aborts input with ^C.
             # Allegedly this behavior is inherited from getpass(3).
@@ -243,12 +260,7 @@ def confirm(
 
     while True:
         try:
-            # Write the prompt separately so that we get nice
-            # coloring through colorama on Windows
-            echo(prompt[:-1], nl=False, err=err)
-            # Echo the last character to stdout to work around an issue where
-            # readline causes backspace to clear the whole line.
-            value = visible_prompt_func(prompt[-1:]).lower().strip()
+            value = _readline_prompt(visible_prompt_func, prompt, err).lower().strip()
         except (KeyboardInterrupt, EOFError):
             raise Abort() from None
         if value in ("y", "yes"):

tests/test_utils.py

@@ -225,7 +225,38 @@ def f(_):
         click.echo("interrupted")
 
     out, err = capsys.readouterr()
-    assert out == "Password:\ninterrupted\n"
+    # On non-Windows, prompt is passed directly to getpass, not echoed separately
+    assert out == "\ninterrupted\n"
+
+
+@pytest.mark.skipif(WIN, reason="Different behavior on windows.")
+@pytest.mark.parametrize(
+    ("call", "expected_prompt"),
+    [
+        (lambda: click.prompt("Name"), "Name: "),
+        (lambda: click.prompt("Pw", hide_input=True), "Pw: "),
+        (lambda: click.prompt("IP", prompt_suffix="."), "IP."),
+        (lambda: click.confirm("OK"), "OK [y/N]: "),
+    ],
+    ids=["prompt", "prompt-hidden", "prompt-custom-suffix", "confirm"],
+)
+def test_full_prompt_passed_to_readline(monkeypatch, call, expected_prompt):
+    """On non-Windows, prompt and confirm pass the full prompt text to the
+    underlying prompt function so readline handles editing correctly.
+
+    https://github.com/pallets/click/issues/2968
+    https://github.com/pallets/click/pull/2969
+    """
+    received = []
+
+    def capture(text):
+        received.append(text)
+        return "y"
+
+    monkeypatch.setattr("click.termui.visible_prompt_func", capture)
+    monkeypatch.setattr("click.termui.hidden_prompt_func", capture)
+    call()
+    assert received == [expected_prompt]
 
 
 def test_prompts_eof(runner):
@@ -484,17 +515,21 @@ def emulate_input(text):
     assert out == "Prompt to stdin with no suffix"
     assert err == ""
 
+    # On non-Windows the full prompt goes through redirect_stdout so
+    # nothing leaks to stdout when err=True.
+    # https://github.com/pallets/click/issues/2968
     emulate_input("asdlkj\n")
     click.prompt("Prompt to stderr", err=True)
     out, err = capfd.readouterr()
-    assert out == " "
-    assert err == "Prompt to stderr:"
+    assert out == ""
+    assert err == "Prompt to stderr: "
 
+    # https://github.com/pallets/click/issues/3019
     emulate_input("asdlkj\n")
     click.prompt("Prompt to stderr with no suffix", prompt_suffix="", err=True)
     out, err = capfd.readouterr()
-    assert out == "x"
-    assert err == "Prompt to stderr with no suffi"
+    assert out == ""
+    assert err == "Prompt to stderr with no suffix"
 
     emulate_input("y\n")
     click.confirm("Prompt to stdin")
@@ -508,17 +543,19 @@ def emulate_input(text):
     assert out == "Prompt to stdin with no suffix [y/N]"
     assert err == ""
 
+    # https://github.com/pallets/click/issues/2968
     emulate_input("y\n")
     click.confirm("Prompt to stderr", err=True)
     out, err = capfd.readouterr()
-    assert out == " "
-    assert err == "Prompt to stderr [y/N]:"
+    assert out == ""
+    assert err == "Prompt to stderr [y/N]: "
 
+    # https://github.com/pallets/click/issues/3019
     emulate_input("y\n")
     click.confirm("Prompt to stderr with no suffix", prompt_suffix="", err=True)
     out, err = capfd.readouterr()
-    assert out == "]"
-    assert err == "Prompt to stderr with no suffix [y/N"
+    assert out == ""
+    assert err == "Prompt to stderr with no suffix [y/N]"
 
     monkeypatch.setattr(click.termui, "isatty", lambda x: True)
     monkeypatch.setattr(click.termui, "getchar", lambda: " ")