Fixed click.prompt not working with readline module

CHANGES.rst

@@ -201,6 +201,8 @@ Unreleased
     applications to translate Click's built-in strings. :issue:`303`
 -   Writing invalid characters  to ``stderr`` when using the test runner
     does not raise a ``UnicodeEncodeError``. :issue:`848`
+-   Fix an issue where ``readline`` would clear the entire ``prompt()``
+    line instead of only the input when pressing backspace. :issue:`665`
 
 
 Version 7.1.2

src/click/termui.py

@@ -127,8 +127,10 @@ def prompt_func(text):
         try:
             # Write the prompt separately so that we get nice
             # coloring through colorama on Windows
-            echo(text, nl=False, err=err)
-            return f("")
+            echo(text.rstrip(" "), nl=False, err=err)
+            # Echo a space to stdout to work around an issue where
+            # readline causes backspace to clear the whole line.
+            return f(" ")
         except (KeyboardInterrupt, EOFError):
             # getpass doesn't print a newline if the user aborts input with ^C.
             # Allegedly this behavior is inherited from getpass(3).

tests/test_utils.py

@@ -154,10 +154,10 @@ def f(_):
     try:
         click.prompt("Password", hide_input=True)
     except click.Abort:
-        click.echo("Screw you.")
+        click.echo("interrupted")
 
     out, err = capsys.readouterr()
-    assert out == "Password: \nScrew you.\n"
+    assert out == "Password:\ninterrupted\n"
 
 
 def _test_gen_func():
@@ -255,8 +255,8 @@ def emulate_input(text):
     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:"
 
     emulate_input("y\n")
     click.confirm("Prompt to stdin")