Add type hints

Author: Daverball

HISTORY.rst

@@ -4,6 +4,10 @@ Changelog
 0.5.2 (unreleased)
 ~~~~~~~~~~~~~~~~~~~
 
+- Minor robustness improvements
+
+- Add type hints
+
 - Switch to PEP-420 namespace package
 
 - Drop support for Python below 3.10

more/webassets/__init__.py

@@ -1 +1,3 @@
-from more.webassets.core import WebassetsApp  # noqa
+from more.webassets.core import WebassetsApp
+
+__all__ = ("WebassetsApp",)

more/webassets/core.py

@@ -1,13 +1,32 @@
-from more.webassets.tweens import InjectorTween, PublisherTween
-from morepath.request import Request
-from morepath.app import App
-from dectate import directive
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
 from ordered_set import OrderedSet
+
+from dectate import directive
+from morepath.app import App
 from morepath.core import excview_tween_factory
+from morepath.request import Request
+
 from . import directives
+from .tweens import InjectorTween, PublisherTween
+
+if TYPE_CHECKING:
+    from typing_extensions import TypeVar
+
+    from morepath.types import Tween
 
+    _AppT = TypeVar(
+        "_AppT", bound="WebassetsApp", default="WebassetsApp", covariant=True
+    )
+else:
+    from typing import TypeVar
 
-class IncludeRequest(Request):
+    _AppT = TypeVar("_AppT", bound="WebassetsApp", covariant=True)
+
+
+class IncludeRequest(Request[_AppT]):
     """Adds the ability to include webassets bundles on the request.
 
     If the bundle does not exist, a KeyError will be raised during the
@@ -27,11 +46,16 @@ def view(self, request):
 
     """
 
-    def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self.included_assets = OrderedSet()
+    included_assets: OrderedSet[str]
+
+    # NOTE: Preserve the signature of the super-class, without duplicating it
+    if not TYPE_CHECKING:
+
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            self.included_assets = OrderedSet()
 
-    def include(self, resource):
+    def include(self, resource: str) -> None:
         self.included_assets.add(resource)
 
 
@@ -54,7 +78,7 @@ class WebassetsApp(App):
 
 
 @WebassetsApp.tween_factory(over=excview_tween_factory)
-def webassets_injector_tween(app, handler):
+def webassets_injector_tween(app: WebassetsApp, handler: Tween) -> Tween:
     """Wraps the response with the injector and the publisher tween.
 
     See :class:`webassets.tweens.InjectorTween` and