From 50aa86b28d5ed6ca0f70c9d769318208062b56c6 Mon Sep 17 00:00:00 2001
From: i2y <6240399+i2y@users.noreply.github.com>
Date: Tue, 22 Sep 2026 21:59:03 +0900
Subject: [PATCH] Give Codec type variables defaults

Generated *_connect.py files annotate their codecs/codec parameters with
a bare Codec, which mypy --strict reports as a missing type argument
([type-arg]) in every generated service file. Give T_contra and U a
PEP 696 default of Any via typing_extensions.TypeVar, so a bare Codec
means Codec[Any, Any] and generated code type-checks without changing
the generator or its output. typing_extensions was already in the
runtime dependency tree through protobuf-py and pyqwest; declare it
directly with the same >=4.13.0 floor protobuf-py uses. This mirrors
bufbuild/protobuf-py#79.

Fixes #341

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: i2y <6240399+i2y@users.noreply.github.com>
---
 pyproject.toml           | 1 +
 src/connectrpc/_codec.py | 7 ++++---
 uv.lock                  | 4 +++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 5d0ad1f7..bc03989c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,6 +31,7 @@ classifiers = [
 dependencies = [
   "protobuf-py>=0.3.0",
   "pyqwest>=0.5.1",
+  "typing_extensions>=4.13.0",
 ]
 
 [project.urls]
diff --git a/src/connectrpc/_codec.py b/src/connectrpc/_codec.py
index 73a3d928..f5df1690 100644
--- a/src/connectrpc/_codec.py
+++ b/src/connectrpc/_codec.py
@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Protocol, TypeVar
+from typing import Any, Protocol
 
 from protobuf import Message, Registry
 from protobuf.wkt import (
@@ -18,6 +18,7 @@
     type_pb,
     wrappers_pb,
 )
+from typing_extensions import TypeVar
 
 CODEC_NAME_PROTO = "proto"
 CODEC_NAME_JSON = "json"
@@ -40,8 +41,8 @@
 )
 
 
-T_contra = TypeVar("T_contra", contravariant=True)
-U = TypeVar("U")
+T_contra = TypeVar("T_contra", contravariant=True, default=Any)
+U = TypeVar("U", default=Any)
 V = TypeVar("V", bound=Message)
 
 
diff --git a/uv.lock b/uv.lock
index 25ac7e29..40993fa5 100644
--- a/uv.lock
+++ b/uv.lock
@@ -158,6 +158,7 @@ source = { editable = "." }
 dependencies = [
     { name = "protobuf-py" },
     { name = "pyqwest" },
+    { name = "typing-extensions" },
 ]
 
 [package.dev-dependencies]
@@ -203,6 +204,7 @@ docs = [
 requires-dist = [
     { name = "protobuf-py", specifier = ">=0.3.0" },
     { name = "pyqwest", specifier = ">=0.5.1" },
+    { name = "typing-extensions", specifier = ">=4.13.0" },
 ]
 
 [package.metadata.requires-dev]
@@ -439,7 +441,7 @@ name = "exceptiongroup"
 version = "1.3.1"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
-    { name = "typing-extensions" },
+    { name = "typing-extensions", marker = "python_full_version < '3.13'" },
 ]
 sdist = { url = "https://files.pythonhosted.org/packages/50/79/66800aadf48771f6b62f7eb014e352e5d06856655206165d775e675a02c9/exceptiongroup-1.3.1.tar.gz", hash = "sha256:8b412432c6055b0b7d14c310000ae93352ed6754f70fa8f7c34141f91c4e3219", size = 30371, upload-time = "2025-11-21T23:01:54.787Z" }
 wheels = [