Make Choice.shortcut_key property with setter

Ensures that `Choice.auto_shortcut` is set to `False`
whenever `Choice.shortcut_key` is set to a `str` value
and vice versa. Add tests for fix.

Closes #340

questionary/prompts/common.py

@@ -116,12 +116,12 @@ def build(c: Union[str, "Choice", Dict[str, Any]]) -> "Choice":
             )
 
     @property
-    def shortcut_key() -> Optional[str]:
+    def shortcut_key(self) -> Optional[str]:
         """A shortcut key for the choice"""
         return self.__shortcut_key
 
     @shortcut_key.setter
-    def shortcut_key(key: Optional[Union[str, bool]]):
+    def shortcut_key(self, key: Optional[Union[str, bool]]):
         if key is not None:
             if isinstance(key, bool):
                 self.auto_shortcut = key
@@ -134,7 +134,7 @@ def shortcut_key(key: Optional[Union[str, bool]]):
             self.auto_shortcut = True
 
     @shortcut_key.deleter
-    def shortcut_key():
+    def shortcut_key(self):
         self.__shortcut_key = None
         self.auto_shortcut = True
 

tests/prompts/test_select.py

@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+from copy import copy
+
 import pytest
 
 from questionary import Choice
@@ -199,6 +201,29 @@ def test_allow_shortcut_key_with_True():
     assert result == "bazz"
 
 
+def test_auto_shortcut_key_stable_in_loop():
+    message = "Foo message"
+    choices = [
+        Choice("foo"),
+        Choice("bar"),
+    ]
+    kwargs = {
+        "choices": choices,
+        "use_shortcuts": True,
+    }
+    text = "\r"
+
+    result, cli = feed_cli_with_input("select", message, text, **kwargs)
+    assert result == "foo"
+    result_shortcut_keys = [copy(c.shortcut_key) for c in choices]
+    result2, cli = feed_cli_with_input("select", message, text, **kwargs)
+    assert result2 == "foo"
+    result2_shortcut_keys = [copy(c.shortcut_key) for c in choices]
+    assert (
+        result_shortcut_keys == result2_shortcut_keys
+    ), "Shortcut keys changed across two runs of 'select'"
+
+
 def test_select_initial_choice_with_value():
     message = "Foo message"
     choice = Choice(title="bazz", value="bar")