refactor: move async dependencies from optional to direct (GoogleCloudPlatform#386)

## Summary
This PR moves starlette, uvicorn, and uvicorn-worker from optional dependencies to direct dependencies, simplifying the installation process for users who need async functionality.

## Impact Analysis
- **Installation size increase: < 1MB** (specifically 816KB, ~3.5% increase)
- Base installation: 23MB → With async deps: 24MB
- Removes the need for `pip install functions-framework[async]`
- Maintains Python 3.8+ requirement for these dependencies

## Changes
- Move async dependencies to direct dependencies in `pyproject.toml`
- Remove `[async]` extra dependency configuration
- Update imports to be direct instead of conditional
- Remove "Starlette is not installed" error messages
- Update tests to reflect direct dependency availability

## Test Plan
All existing tests pass with 100% coverage. The async functionality remains unchanged, just the installation method is simplified.

Author: taeold

.github/workflows/conformance-asgi.yml

@@ -39,8 +39,8 @@ jobs:
       with:
         python-version: ${{ matrix.python }}
 
-    - name: Install the framework with async extras
-      run: python -m pip install -e .[async]
+    - name: Install the framework
+      run: python -m pip install -e .
 
     - name: Setup Go
       uses: actions/setup-go@d35c59abb061a4a6fb18e82ac0862c26744d6ab5 # v5.5.0

pyproject.toml

@@ -30,18 +30,14 @@ dependencies = [
   "cloudevents>=1.2.0,<=1.11.0",                  # Must support python 3.7
   "Werkzeug>=0.14,<4.0.0",
   "httpx>=0.24.1",
+  "starlette>=0.37.0,<1.0.0; python_version>='3.8'",
+  "uvicorn>=0.18.0,<1.0.0; python_version>='3.8'",
+  "uvicorn-worker>=0.2.0,<1.0.0; python_version>='3.8'",
 ]
 
 [project.urls]
 Homepage = "https://github.com/googlecloudplatform/functions-framework-python"
 
-[project.optional-dependencies]
-async = [
-    "starlette>=0.37.0,<1.0.0; python_version>='3.8'",
-    "uvicorn>=0.18.0,<1.0.0; python_version>='3.8'",
-    "uvicorn-worker>=0.2.0,<1.0.0; python_version>='3.8'"
-]
-
 [project.scripts]
 ff = "functions_framework._cli:_cli"
 functions-framework = "functions_framework._cli:_cli"

src/functions_framework/aio/__init__.py

@@ -25,6 +25,12 @@
 
 from cloudevents.http import from_http
 from cloudevents.http.event import CloudEvent
+from starlette.applications import Starlette
+from starlette.exceptions import HTTPException
+from starlette.middleware import Middleware
+from starlette.requests import Request
+from starlette.responses import JSONResponse, Response
+from starlette.routing import Route
 
 from functions_framework import (
     _enable_execution_id_logging,
@@ -36,19 +42,6 @@
     MissingSourceException,
 )
 
-try:
-    from starlette.applications import Starlette
-    from starlette.exceptions import HTTPException
-    from starlette.middleware import Middleware
-    from starlette.requests import Request
-    from starlette.responses import JSONResponse, Response
-    from starlette.routing import Route
-except ImportError:
-    raise FunctionsFrameworkException(
-        "Starlette is not installed. Install the framework with the 'async' extra: "
-        "pip install functions-framework[async]"
-    )
-
 HTTPResponse = Union[
     Response,  # Functions can return a full Starlette Response object
     str,  # Str returns are wrapped in Response(result)

tests/test_aio.py

@@ -35,29 +35,6 @@
 TEST_FUNCTIONS_DIR = pathlib.Path(__file__).resolve().parent / "test_functions"
 
 
-def test_import_error_without_starlette(monkeypatch):
-    import builtins
-
-    original_import = builtins.__import__
-
-    def mock_import(name, *args, **kwargs):
-        if name.startswith("starlette"):
-            raise ImportError(f"No module named '{name}'")
-        return original_import(name, *args, **kwargs)
-
-    monkeypatch.setattr(builtins, "__import__", mock_import)
-
-    # Remove the module from sys.modules to force re-import
-    if "functions_framework.aio" in sys.modules:
-        del sys.modules["functions_framework.aio"]
-
-    with pytest.raises(exceptions.FunctionsFrameworkException) as excinfo:
-        import functions_framework.aio
-
-    assert "Starlette is not installed" in str(excinfo.value)
-    assert "pip install functions-framework[async]" in str(excinfo.value)
-
-
 def test_invalid_function_definition_missing_function_file():
     source = TEST_FUNCTIONS_DIR / "missing_function_file" / "main.py"
     target = "function"

tests/test_asgi.py

@@ -18,12 +18,9 @@
 import pretend
 import pytest
 
-import functions_framework._http
+from starlette.applications import Starlette
 
-try:
-    from starlette.applications import Starlette
-except ImportError:
-    pass
+import functions_framework._http
 
 
 def test_httpserver_detects_asgi_app():

tox.ini

@@ -29,8 +29,6 @@ deps =
     pytest-cov
     pytest-integration
     pretend
-extras =
-    async
 setenv =
     PYTESTARGS = --cov=functions_framework --cov-branch --cov-report term-missing --cov-fail-under=100
     # Python 3.7: Use .coveragerc-py37 to exclude aio module from coverage since it requires Python 3.8+ (Starlette dependency)
@@ -48,8 +46,6 @@ deps =
     isort
     mypy
     build
-extras =
-    async
 commands =
     black --check src tests conftest.py --exclude tests/test_functions/background_load_error/main.py
     isort -c src tests conftest.py