Mypy upgrade and refactoring

requirements/mypy.txt

@@ -1,3 +1,3 @@
-mypy==1.15.0
+mypy==1.16.1
 mypy-zope==1.0.12
 types-click==7.1.8

src/klein/_app.py

@@ -514,8 +514,7 @@ def error_handler(request, failure):
             f_or_exception, Exception
         ):
             # f_or_exception is a KleinErrorHandler
-            f = cast(KleinErrorHandler, f_or_exception)
-            return self.handle_errors(Exception)(f)
+            return self.handle_errors(Exception)(f_or_exception)
 
         # f_or_exception is an Exception class
         exceptions = [f_or_exception] + list(additional_exceptions)

src/klein/_resource.py

@@ -4,6 +4,7 @@
 from typing import TYPE_CHECKING, Any, Optional, Sequence, Tuple, Union, cast
 
 from werkzeug.exceptions import HTTPException
+from werkzeug.wrappers.response import Response as WerkResponse
 
 from twisted.internet import defer
 from twisted.internet.defer import Deferred, maybeDeferred, succeed
@@ -23,7 +24,6 @@
     from ._app import (
         ErrorMethods,
         Klein,
-        KleinRenderable,
         KleinRouteHandler,
         RouteMetadata,
     )
@@ -159,8 +159,27 @@ def __ne__(self, other: object) -> bool:
             return result
         return not result
 
-    def render(self, request: IRequest) -> KleinRenderable:
-        # Stuff we need to know for the mapper.
+    def render(self, request: IRequest) -> int | bytes:
+        """
+        Render the request based on the underlying L{Klein} application, in a
+        multi-step process:
+
+            1. convert twisted input request information into something legible
+               to werkzeug
+
+            2. bind that info (URL, method, query args, etc) into a request
+               mapper, and look up a werkzeug endpoint (i.e.: klein
+               C{@route}-decorated method) to invoke
+
+            3. invoke that endpoint, getting something renderable
+
+            4. render that thing
+
+            5. handle any errors in lookup or rendering with declared error
+               handlers
+
+            6. render the thing that the error handler returned
+        """
         try:
             (
                 url_scheme,
@@ -231,8 +250,9 @@ def _execute() -> Deferred:
         def process(r: object) -> Any:
             """
             Recursively go through r and any child Resources until something
-            returns an IRenderable, then render it and let the result of that
-            bubble back up.
+            returns something renderable (L{IResource}, L{IRenderable},
+            L{bytes}, L{str}, or L{Iterable} of same), then render it and let
+            the result of that bubble back up.
             """
             # isinstance() is faster than providedBy(), so this speeds up the
             # very common case of returning pre-rendered results, at the cost
@@ -279,14 +299,19 @@ def processing_failed(
                     he = failure.value
                     assert isinstance(he, HTTPException)
                     request.setResponseCode(he.code)
-                    resp = he.get_response({})
+
+                    # we need to call iter_encoded later so we need to include
+                    # an explicit workaround for
+                    # https://github.com/pallets/werkzeug/issues/3056
+                    resp: WerkResponse
+                    resp = he.get_response({})  # type:ignore[assignment]
 
                     for header, value in resp.headers:
                         request.setHeader(
                             ensure_utf8_bytes(header), ensure_utf8_bytes(value)
                         )
 
-                    encoded = resp.iter_encoded()  # type: ignore[attr-defined]
+                    encoded = resp.iter_encoded()
                     return succeed(ensure_utf8_bytes(b"".join(encoded)))
                 else:
                     request.processingFailed(  # type: ignore[attr-defined]
@@ -333,4 +358,4 @@ def write_response(
         d.addCallback(write_response)
         d.addErrback(log.err, _why="Unhandled Error writing response")
 
-        return server.NOT_DONE_YET  # type: ignore[return-value]
+        return server.NOT_DONE_YET