add httpx to optional deps and only ship tests in sdist

README.md

@@ -313,6 +313,8 @@ The default HTTP client uses `requests` for making synchronous requests but
 you to explicitly initialize your own http client and pass it to StripeClient
 or set it as the global default.
 
+If you don't already have a dependency on an async-compatible HTTP library, `pip install stripe[async]` will install one for you (new in `v13.0.1`).
+
 ```python
 # By default, an explicitly initialized HTTPXClient will raise an exception if you
 # attempt to call a sync method. If you intend to only use async, this is useful to

pyproject.toml

@@ -7,13 +7,6 @@ authors = [{ name = "Stripe", email = "support@stripe.com" }]
 license-files = ["LICENSE"]
 keywords = ["stripe", "api", "payments"]
 requires-python = ">=3.7"
-dependencies = [
-  "typing_extensions <= 4.2.0, > 3.7.2; python_version < '3.7'",
-  # The best typing support comes from 4.5.0+ but we can support down to
-  # 3.7.2 without throwing exceptions.
-  "typing_extensions >= 4.5.0; python_version >= '3.7'",
-  "requests >= 2.20; python_version >= '3.0'",
-]
 classifiers = [
   "Development Status :: 5 - Production/Stable",
   "Intended Audience :: Developers",
@@ -33,6 +26,18 @@ classifiers = [
   "Topic :: Software Development :: Libraries :: Python Modules",
 ]
 
+dependencies = [
+  "typing_extensions <= 4.2.0, > 3.7.2; python_version < '3.7'",
+  # The best typing support comes from 4.5.0+ but we can support down to
+  # 3.7.2 without throwing exceptions.
+  "typing_extensions >= 4.5.0; python_version >= '3.7'",
+  "requests >= 2.20; python_version >= '3.0'",
+]
+
+[project.optional-dependencies]
+# `pip install stripe[async]` gets you everything + `httpx`, so our async stuff works out of the box
+async = ["httpx"]
+
 [project.urls]
 homepage = "https://stripe.com/"
 source = "https://github.com/stripe/stripe-python"
@@ -45,7 +50,8 @@ requires = ["flit_core >=3.11, <4"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.sdist]
-include = ["tests/", "justfile", "examples/", "CHANGELOG.md", "deps/"]
+# see: https://github.com/stripe/stripe-python/issues/1616
+include = ["tests/"]
 
 [tool.ruff]
 # same as our black config