Update suggester implementation.

src/textual/suggester.py

@@ -4,7 +4,7 @@ from abc import ABC, abstractmethod
 from dataclasses import dataclass
 from typing import Iterable
 
-from ._cache import FIFOCache
+from ._cache import LRUCache
 from .dom import DOMNode
 from .message import Message
 
@@ -13,7 +13,7 @@ from .message import Message
 class SuggestionReady(Message):
     """Sent when a completion suggestion is ready."""
 
-    initial_value: str
+    value: str
     """The value to which the suggestion is for."""
     suggestion: str
     """The string suggestion."""
@@ -27,16 +27,20 @@ class Suggester(ABC):
     See [`SuggestFromList`][textual.suggester.SuggestFromList] for an example.
     """
 
-    cache: FIFOCache[str, str | None] | None
+    cache: LRUCache[str, str | None] | None
     """Suggestion cache, if used."""
 
-    def __init__(self, use_cache: bool = True) -> None:
+    def __init__(self, *, use_cache: bool = True, case_sensitive: bool = True) -> None:
         """Create a suggester object.
 
         Args:
             use_cache: Whether to cache suggestion results.
+            case_sensitive: Whether suggestions are case sensitive or not.
+                If they are not, incoming values are casefolded before generating
+                the suggestion.
         """
-        self.cache = FIFOCache(1024) if use_cache else None
+        self.cache = LRUCache(1024) if use_cache else None
+        self.case_sensitive = case_sensitive
 
     async def _get_suggestion(self, requester: DOMNode, value: str) -> None:
         """Used by widgets to get completion suggestions.
@@ -47,15 +51,16 @@ class Suggester(ABC):
 
         Args:
             requester: The message target that requested a suggestion.
-            value: The current input value to complete.
+            value: The current value to complete.
         """
 
-        if self.cache is None or value not in self.cache:
+        normalized_value = value if self.case_sensitive else value.casefold()
-            suggestion = await self.get_suggestion(value)
+        if self.cache is None or normalized_value not in self.cache:
+            suggestion = await self.get_suggestion(normalized_value)
             if self.cache is not None:
-                self.cache[value] = suggestion
+                self.cache[normalized_value] = suggestion
         else:
-            suggestion = self.cache[value]
+            suggestion = self.cache[normalized_value]
 
         if suggestion is None:
             return
@@ -67,6 +72,9 @@ class Suggester(ABC):
 
         Custom suggesters should implement this method.
 
+        Note:
+            The value argument will be casefolded if `self.case_sensitive` is `False`.
+
         Note:
             If your implementation is not deterministic, you may need to disable caching.
 
@@ -88,18 +96,32 @@ class SuggestFromList(Suggester):
 
         class MyApp(App[None]):
             def compose(self) -> ComposeResult:
-                yield Input(suggester=SuggestFromList(countries))
+                yield Input(suggester=SuggestFromList(countries, case_sensitive=False))
         ```
+
+        If the user types ++p++ inside the input widget, a completion suggestion
+        for `"Portugal"` appears.
     """
 
-    def __init__(self, suggestions: Iterable[str]) -> None:
+    def __init__(
+        self, suggestions: Iterable[str], *, case_sensitive: bool = True
+    ) -> None:
         """Creates a suggester based off of a given iterable of possibilities.
 
         Args:
             suggestions: Valid suggestions sorted by decreasing priority.
+            case_sensitive: Whether suggestions are computed in a case sensitive manner
+                or not. The values provided in the argument `suggestions` represent the
+                canonical representation of the completions and they will be suggested
+                with that same casing.
         """
-        super().__init__()
+        super().__init__(case_sensitive=case_sensitive)
         self._suggestions = list(suggestions)
+        self._for_comparison = (
+            self._suggestions
+            if self.case_sensitive
+            else [suggestion.casefold() for suggestion in self._suggestions]
+        )
 
     async def get_suggestion(self, value: str) -> str | None:
         """Gets a completion from the given possibilities.
@@ -110,7 +132,7 @@ class SuggestFromList(Suggester):
         Returns:
             A valid completion suggestion or `None`.
         """
-        for suggestion in self._suggestions:
+        for idx, suggestion in enumerate(self._for_comparison):
             if suggestion.startswith(value):
-                return suggestion
+                return self._suggestions[idx]
         return None

src/textual/widgets/_input.py

@@ -38,9 +38,7 @@ class _InputRenderable:
         value = input.value
         value_length = len(value)
         suggestion = input._suggestion
-        show_suggestion = suggestion.startswith(value) and (
+        show_suggestion = len(suggestion) > value_length
-            len(suggestion) > value_length
-        )
         if show_suggestion:
             result += Text(
                 suggestion[value_length:],
@@ -388,7 +386,7 @@ class Input(Widget, can_focus=True):
 
     async def _on_suggestion_ready(self, event: SuggestionReady) -> None:
         """Handle suggestion messages and set the suggestion when relevant."""
-        if event.initial_value == self.value:
+        if event.value == self.value:
             self._suggestion = event.suggestion
 
     def insert_text_at_cursor(self, text: str) -> None: