Prefix filter search

questionary/constants.py

@@ -35,6 +35,7 @@
         ("qmark", "fg:#5f819d"),  # token in front of the question
         ("question", "bold"),  # question text
         ("answer", "fg:#FF9D00 bold"),  # submitted answer text behind the question
+        ("search", "noinherit fg:#FF6600 bold"),  # submitted answer text behind the question
         ("pointer", ""),  # pointer used in select and checkbox prompts
         ("selected", ""),  # style for a selected item of a checkbox
         ("separator", ""),  # separator in lists

questionary/prompts/common.py

@@ -1,14 +1,16 @@
 # -*- coding: utf-8 -*-
 import inspect
 from prompt_toolkit import PromptSession
-from prompt_toolkit.filters import IsDone, Always
+from prompt_toolkit.filters import Always, Condition, IsDone
+from prompt_toolkit.keys import Keys
 from prompt_toolkit.layout import (
     FormattedTextControl,
     Layout,
     HSplit,
     ConditionalContainer,
     Window,
 )
+from prompt_toolkit.layout.dimension import LayoutDimension as D
 from prompt_toolkit.validation import Validator, ValidationError
 from typing import Optional, Any, List, Text, Dict, Union, Callable, Tuple
 
@@ -155,6 +157,7 @@ def __init__(
         self.is_answered = False
         self.choices = []
         self.selected_options = []
+        self.prefix_search_filter = None
 
         self._init_choices(choices)
         self._assign_shortcut_keys()
@@ -208,9 +211,18 @@ def _init_choices(self, choices):
 
             self.choices.append(choice)
 
+    @property
+    def filtered_choices(self):
+        if not self.prefix_search_filter:
+            return self.choices
+        else:
+            return [
+                c for c in self.choices if c.title.startswith(self.prefix_search_filter)
+            ]
+
     @property
     def choice_count(self):
-        return len(self.choices)
+        return len(self.filtered_choices)
 
     def _get_choice_tokens(self):
         tokens = []
@@ -292,7 +304,7 @@ def append(index, choice):
             tokens.append(("", "\n"))
 
         # prepare the select choices
-        for i, c in enumerate(self.choices):
+        for i, c in enumerate(self.filtered_choices):
             append(i, c)
 
         if self.use_shortcuts:
@@ -323,7 +335,7 @@ def select_next(self):
         self.pointed_at = (self.pointed_at + 1) % self.choice_count
 
     def get_pointed_at(self):
-        return self.choices[self.pointed_at]
+        return self.filtered_choices[self.pointed_at]
 
     def get_selected_values(self):
         # get values not labels
@@ -333,6 +345,35 @@ def get_selected_values(self):
             if (not isinstance(c, Separator) and c.value in self.selected_options)
         ]
 
+    def add_search_character(self, char: Keys) -> None:
+        if char == Keys.Backspace:
+            self.remove_search_character()
+        else:
+            if self.prefix_search_filter is None:
+                self.prefix_search_filter = str(char)
+            else:
+                self.prefix_search_filter += str(char)
+
+        # Make sure that the selection is in the bounds of the filtered list
+        self.pointed_at = 0
+
+    def remove_search_character(self) -> None:
+        if self.prefix_search_filter and len(self.prefix_search_filter) > 1:
+            self.prefix_search_filter = self.prefix_search_filter[:-1]
+        else:
+            self.prefix_search_filter = None
+
+    def get_search_string_tokens(self):
+        if self.prefix_search_filter is None:
+            return None
+
+        return [
+            ('', '\n'),
+            ('class:question-mark', '/ '),
+            ('class:search', self.prefix_search_filter),
+            ('class:question-mark', '...'),
+        ]
+
 
 def build_validator(validate: Any) -> Optional[Validator]:
     if validate:
@@ -385,8 +426,22 @@ def create_inquirer_layout(
 
     _fix_unecessary_blank_lines(ps)
 
+    @Condition
+    def has_search_string():
+        return ic.get_search_string_tokens() is not None
+
     return Layout(
         HSplit(
-            [ps.layout.container, ConditionalContainer(Window(ic), filter=~IsDone())]
+            [
+                ps.layout.container,
+                ConditionalContainer(Window(ic), filter=~IsDone()),
+                ConditionalContainer(
+                    Window(
+                        height=D.exact(2),
+                        content=FormattedTextControl(ic.get_search_string_tokens)
+                    ),
+                    filter=has_search_string & ~IsDone()    # noqa  # pylint:disable=invalid-unary-operand-type
+                ),
+            ]
         )
     )

questionary/prompts/select.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-
+import string
 from typing import Any, Dict, List, Optional, Text, Union
 
 from prompt_toolkit.application import Application
@@ -22,6 +22,7 @@ def select(
     use_shortcuts: bool = False,
     use_indicator: bool = False,
     use_pointer: bool = True,
+    use_prefix_filter_search: bool = False,
     instruction: Text = None,
     **kwargs: Any
 ) -> Question:
@@ -59,6 +60,13 @@ def select(
 
         use_pointer: Flag to enable the pointer in front of the currently
                      highlighted element.
+
+        use_prefix_filter_search: Flag to enable prefix filter. Typing some prefix will
+                                  filter the choices to keep only the one that match
+                                  the prefix.
+                                  Note that activating this option disables "vi-like"
+                                  navigation as "j" and "k" can be part of a prefix and
+                                  therefore cannot be used for navigation
     Returns:
         Question: Question instance, ready to be prompted (using `.ask()`).
     """
@@ -138,19 +146,29 @@ def select_choice(event):
     else:
 
         @bindings.add(Keys.Down, eager=True)
-        @bindings.add("j", eager=True)
         def move_cursor_down(event):
             ic.select_next()
             while not ic.is_selection_valid():
                 ic.select_next()
 
         @bindings.add(Keys.Up, eager=True)
-        @bindings.add("k", eager=True)
         def move_cursor_up(event):
             ic.select_previous()
             while not ic.is_selection_valid():
                 ic.select_previous()
 
+        if use_prefix_filter_search:
+            def search_filter(event):
+                ic.add_search_character(event.key_sequence[0].key)
+
+            for character in string.printable:
+                bindings.add(character, eager=True)(search_filter)
+            bindings.add(Keys.Backspace, eager=True)(search_filter)
+        else:
+            # Enable vi-like navigation
+            bindings.add("j", eager=True)(move_cursor_down)
+            bindings.add("k", eager=True)(move_cursor_up)
+
     @bindings.add(Keys.ControlM, eager=True)
     def set_answer(event):
         ic.is_answered = True

tests/prompts/test_select.py

@@ -144,3 +144,60 @@ def test_select_empty_choices():
 
     with pytest.raises(ValueError):
         feed_cli_with_input("select", message, text, **kwargs)
+
+
+def test_filter_prefix_one_letter():
+    message = "Foo message"
+    kwargs = {"choices": ["abc", "def", "ghi", "jkl"]}
+    text = "g" + KeyInputs.ENTER + "\r"
+
+    result, cli = feed_cli_with_input(
+        "select", message, text, use_prefix_filter_search=True, **kwargs
+    )
+    assert result == "ghi"
+
+
+def test_filter_prefix_multiple_letters():
+    message = "Foo message"
+    kwargs = {"choices": ["abc", "def", "ghi", "jkl", "jag", "jja"]}
+    text = "j" + "j" + KeyInputs.ENTER + "\r"
+
+    result, cli = feed_cli_with_input(
+        "select", message, text, use_prefix_filter_search=True, **kwargs
+    )
+    assert result == "jja"
+
+
+def test_select_filter_handle_backspace():
+    message = "Foo message"
+    kwargs = {"choices": ["abc", "def", "ghi", "jkl", "jag", "jja"]}
+    text = "j" + "j" + KeyInputs.BACK + KeyInputs.ENTER + "\r"
+
+    result, cli = feed_cli_with_input(
+        "select", message, text, use_prefix_filter_search=True, **kwargs
+    )
+    assert result == "jkl"
+
+    message = "Foo message"
+    kwargs = {"choices": ["abc", "def", "ghi", "jkl", "jag", "jja"]}
+    text = (
+        "j" + "j" +
+        KeyInputs.BACK + KeyInputs.BACK + KeyInputs.BACK + KeyInputs.BACK +
+        KeyInputs.ENTER + "\r"
+    )
+
+    result, cli = feed_cli_with_input(
+        "select", message, text, use_prefix_filter_search=True, **kwargs
+    )
+    assert result == "abc"
+
+
+def test_select_goes_back_to_top_after_filtering():
+    message = "Foo message"
+    kwargs = {"choices": ["abc", "def", "ghi", "jkl", "jag", "jja"]}
+    text = KeyInputs.DOWN + KeyInputs.DOWN + "j" + KeyInputs.ENTER + "\r"
+
+    result, cli = feed_cli_with_input(
+        "select", message, text, use_prefix_filter_search=True, **kwargs
+    )
+    assert result == "jkl"

tests/utils.py

@@ -27,7 +27,7 @@ def feed_cli_with_input(_type, message, texts, sleep_time=1, **kwargs):
     Create a Prompt, feed it with the given user input and return the CLI
     object.
 
-    You an provide multiple texts, the feeder will async sleep for `sleep_time`
+    You can provide multiple texts, the feeder will async sleep for `sleep_time`
 
     This returns a (result, Application) tuple.
     """