[perf] Widget classes lazy-loading follows a convention, rather than being implemented as a mapping

src/textual/widgets/__init__.py

@@ -2,44 +2,40 @@ from __future__ import annotations
 from importlib import import_module
 import typing
 
+from ..case import camel_to_snake
+
 if typing.TYPE_CHECKING:
     from ..widget import Widget
 
-# Let's decrease startup time by lazy loading our Widgets:
-# ⚠ For any new built-in Widget we create, not only we have to add them to the following dictionary, but also to the
+
+# ⚠️For any new built-in Widget we create, not only we have to add them to the following list, but also to the
 # `__init__.pyi` file in this same folder - otherwise text editors and type checkers won't be able to "see" them.
-_WIDGETS_LAZY_LOADING_MAPPING: dict[str, str] = {
-    "Footer": "._footer:Footer",
-    "Header": "._header:Header",
-    "Button": "._button:Button",
-    "Placeholder": "._placeholder:Placeholder",
-    "Static": "._static:Static",
-    "TreeControl": "._tree_control:TreeControl",
-    "TreeClick": "._tree_control:TreeClick",
-    "TreeNode": "._tree_control:TreeNode",
-    "NodeID": "._tree_control:NodeID",
-    "DirectoryTree": "._directory_tree:DirectoryTree",
-    "FileClick": "._directory_tree:FileClick",
-}
+__all__ = [
+    "Button",
+    "DirectoryTree",
+    "Footer",
+    "Header",
+    "Placeholder",
+    "Static",
+    "TreeControl",
+]
+
 
 _WIDGETS_LAZY_LOADING_CACHE: dict[str, type[Widget]] = {}
 
-
-def __getattr__(widget_name: str) -> type[Widget]:
+# Let's decrease startup time by lazy loading our Widgets:
+def __getattr__(widget_class: str) -> type[Widget]:
     try:
-        return _WIDGETS_LAZY_LOADING_CACHE[widget_name]
+        return _WIDGETS_LAZY_LOADING_CACHE[widget_class]
     except KeyError:
         pass
 
-    if widget_name not in _WIDGETS_LAZY_LOADING_MAPPING:
-        raise ImportError(f"Widget {widget_name} not found")
+    if widget_class not in __all__:
+        raise ImportError(f"Package 'textual.widgets' has no class '{widget_class}'")
 
-    module_name, class_name = _WIDGETS_LAZY_LOADING_MAPPING[widget_name].split(":")
-    module = import_module(module_name, package="textual.widgets")
-    class_ = getattr(module, class_name)
+    widget_module_path = f"._{camel_to_snake(widget_class)}"
+    module = import_module(widget_module_path, package="textual.widgets")
+    class_ = getattr(module, widget_class)
 
-    _WIDGETS_LAZY_LOADING_CACHE[widget_name] = class_
+    _WIDGETS_LAZY_LOADING_CACHE[widget_class] = class_
     return class_
-
-
-__all__ = tuple(_WIDGETS_LAZY_LOADING_MAPPING.keys())

src/textual/widgets/__init__.pyi

@@ -1,12 +1,8 @@
+# This stub file must re-export every classes exposed in the __init__.py's `__all__` list:
+from ._button import Button as Button
+from ._directory_tree import DirectoryTree as DirectoryTree
 from ._footer import Footer as Footer
 from ._header import Header as Header
-from ._button import Button as Button
 from ._placeholder import Placeholder as Placeholder
 from ._static import Static as Static
-from ._tree_control import (
-    TreeControl as TreeControl,
-    TreeClick as TreeClick,
-    TreeNode as TreeNode,
-    NodeID as NodeID,
-)
-from ._directory_tree import DirectoryTree as DirectoryTree, FileClick as FileClick
+from ._tree_control import TreeControl as TreeControl