Improve import time (#6591)

See
aio-libs/aiohttp-debugtoolbar#394 (comment)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Sviatoslav Sydorenko <sviat@redhat.com>

.coveragerc

@@ -0,0 +1,4 @@
+[run]
+branch = True
+source = aiohttp, tests
+omit = site-packages

CHANGES/6591.misc

@@ -0,0 +1 @@
+Changed importing Gunicorn to happen on-demand, decreasing import time by ~53% -- :user:`Dreamsorcerer`.

aiohttp/__init__.py

@@ -1,6 +1,6 @@
 __version__ = "4.0.0a2.dev0"
 
-from typing import Tuple
+from typing import TYPE_CHECKING, Tuple
 
 from . import hdrs as hdrs
 from .client import (
@@ -103,6 +103,13 @@
     TraceResponseChunkReceivedParams as TraceResponseChunkReceivedParams,
 )
 
+if TYPE_CHECKING:
+    # At runtime these are lazy-loaded at the bottom of the file.
+    from .worker import (
+        GunicornUVLoopWebWorker as GunicornUVLoopWebWorker,
+        GunicornWebWorker as GunicornWebWorker,
+    )
+
 __all__: Tuple[str, ...] = (
     "hdrs",
     # client
@@ -203,11 +210,28 @@
     "TraceRequestRedirectParams",
     "TraceRequestStartParams",
     "TraceResponseChunkReceivedParams",
+    # workers (imported lazily with __getattr__)
+    "GunicornUVLoopWebWorker",
+    "GunicornWebWorker",
 )
 
-try:
-    from .worker import GunicornUVLoopWebWorker, GunicornWebWorker
 
-    __all__ += ("GunicornWebWorker", "GunicornUVLoopWebWorker")
-except ImportError:  # pragma: no cover
-    pass
+def __dir__() -> Tuple[str, ...]:
+    return __all__ + ("__author__", "__doc__")
+
+
+def __getattr__(name: str) -> object:
+    global GunicornUVLoopWebWorker, GunicornWebWorker
+
+    # Importing gunicorn takes a long time (>100ms), so only import if actually needed.
+    if name in ("GunicornUVLoopWebWorker", "GunicornWebWorker"):
+        try:
+            from .worker import GunicornUVLoopWebWorker as guv, GunicornWebWorker as gw
+        except ImportError:
+            return None
+
+        GunicornUVLoopWebWorker = guv  # type: ignore[misc]
+        GunicornWebWorker = gw  # type: ignore[misc]
+        return guv if name == "GunicornUVLoopWebWorker" else gw
+
+    raise AttributeError(f"module {__name__} has no attribute {name}")

requirements/constraints.txt

@@ -151,7 +151,7 @@ pyjwt==2.3.0
     # via gidgethub
 pyparsing==2.4.7
     # via packaging
-pytest==7.1.3
+pytest==6.2.5
     # via
     #   -r requirements/lint.txt
     #   -r requirements/test.txt

requirements/lint.txt

@@ -2,5 +2,5 @@
 aioredis==2.0.1
 mypy==0.982; implementation_name=="cpython"
 pre-commit==2.17.0
-pytest==7.1.3
+pytest==6.2.5
 slotscheck==0.8.0

requirements/test.txt

@@ -6,7 +6,7 @@ freezegun==1.1.0
 mypy==0.982; implementation_name=="cpython"
 mypy-extensions==0.4.3; implementation_name=="cpython"
 proxy.py ~= 2.4.4rc3
-pytest==7.1.3
+pytest==6.2.5
 pytest-cov==3.0.0
 pytest-mock==3.6.1
 python-on-whales==0.36.1

setup.cfg

@@ -104,11 +104,6 @@ exclude_lines =
     @abc.abstractmethod
     @abstractmethod
 
-[coverage:run]
-branch = True
-source = aiohttp, tests
-omit = site-packages
-
 [tool:pytest]
 addopts =
     # show 10 slowest invocations:

tests/test_imports.py

@@ -0,0 +1,52 @@
+import os
+import platform
+import sys
+from pathlib import Path
+
+import pytest
+
+
+def test___all__(pytester: pytest.Pytester) -> None:
+    """See https://github.com/aio-libs/aiohttp/issues/6197"""
+    pytester.makepyfile(
+        test_a="""
+            from aiohttp import *
+            assert 'GunicornWebWorker' in globals()
+        """
+    )
+    result = pytester.runpytest("-vv")
+    result.assert_outcomes(passed=0, errors=0)
+
+
+def test_web___all__(pytester: pytest.Pytester) -> None:
+    pytester.makepyfile(
+        test_b="""
+            from aiohttp.web import *
+        """
+    )
+    result = pytester.runpytest("-vv")
+    result.assert_outcomes(passed=0, errors=0)
+
+
+@pytest.mark.skipif(
+    not sys.platform.startswith("linux") or platform.python_implementation() == "PyPy",
+    reason="Timing is more reliable on Linux",
+)
+def test_import_time(pytester: pytest.Pytester) -> None:
+    """Check that importing aiohttp doesn't take too long.
+
+    Obviously, the time may vary on different machines and may need to be adjusted
+    from time to time, but this should provide an early warning if something is
+    added that significantly increases import time.
+    """
+    root = Path(__file__).parent.parent
+    old_path = os.environ.get("PYTHONPATH")
+    os.environ["PYTHONPATH"] = os.pathsep.join([str(root)] + sys.path)
+    r = pytester.run(sys.executable, "-We", "-c", "import aiohttp", timeout=0.41)
+    if old_path is None:
+        os.environ.pop("PYTHONPATH")
+    else:
+        os.environ["PYTHONPATH"] = old_path
+
+    assert not r.stdout.str()
+    assert not r.stderr.str()