https://github.com/python/cpython/commit/39ee468e092eed659bfc2a4e0ce02572e0d81de0
commit: 39ee468e092eed659bfc2a4e0ce02572e0d81de0
branch: main
author: Jelle Zijlstra <jelle.zijls...@gmail.com>
committer: JelleZijlstra <jelle.zijls...@gmail.com>
date: 2025-04-17T03:46:36Z
summary:
gh-118761: Add helper to ensure that lazy imports are actually lazy (#132614)
This ensures that if we jump through some hoops to make sure something is
imported
lazily, we don't regress on importing it.
I recently already accidentally made typing import warnings and annotationlib
eagerly.
Co-authored-by: Adam Turner <9087854+aa-tur...@users.noreply.github.com>
files:
M Lib/test/support/import_helper.py
M Lib/test/test_annotationlib.py
M Lib/test/test_typing.py
diff --git a/Lib/test/support/import_helper.py
b/Lib/test/support/import_helper.py
index 2b91bdcf9cd859..42cfe9cfa8cb72 100644
--- a/Lib/test/support/import_helper.py
+++ b/Lib/test/support/import_helper.py
@@ -5,6 +5,7 @@
import os
import shutil
import sys
+import textwrap
import unittest
import warnings
@@ -309,3 +310,25 @@ def ready_to_import(name=None, source=""):
sys.modules[name] = old_module
else:
sys.modules.pop(name, None)
+
+
+def ensure_lazy_imports(imported_module, modules_to_block):
+ """Test that when imported_module is imported, none of the modules in
+ modules_to_block are imported as a side effect."""
+ modules_to_block = frozenset(modules_to_block)
+ script = textwrap.dedent(
+ f"""
+ import sys
+ modules_to_block = {modules_to_block}
+ if unexpected := modules_to_block & sys.modules.keys():
+ startup = ", ".join(unexpected)
+ raise AssertionError(f'unexpectedly imported at startup:
{{startup}}')
+
+ import {imported_module}
+ if unexpected := modules_to_block & sys.modules.keys():
+ after = ", ".join(unexpected)
+ raise AssertionError(f'unexpectedly imported after importing
{imported_module}: {{after}}')
+ """
+ )
+ from .script_helper import assert_python_ok
+ assert_python_ok("-S", "-c", script)
diff --git a/Lib/test/test_annotationlib.py b/Lib/test/test_annotationlib.py
index 6f097c07295f3b..0890be529a7e52 100644
--- a/Lib/test/test_annotationlib.py
+++ b/Lib/test/test_annotationlib.py
@@ -24,6 +24,7 @@
)
from test import support
+from test.support import import_helper
from test.test_inspect import inspect_stock_annotations
from test.test_inspect import inspect_stringized_annotations
from test.test_inspect import inspect_stringized_annotations_2
@@ -1367,3 +1368,9 @@ def test_multiple_ways_to_create(self):
class TestAnnotationLib(unittest.TestCase):
def test__all__(self):
support.check__all__(self, annotationlib)
+
+ def test_lazy_imports(self):
+ import_helper.ensure_lazy_imports("annotationlib", {
+ "typing",
+ "warnings",
+ })
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 32f12a3f8b22f1..81474a81be645d 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -6317,6 +6317,15 @@ def test_collect_parameters(self):
typing._collect_parameters
self.assertEqual(cm.filename, __file__)
+ def test_lazy_import(self):
+ import_helper.ensure_lazy_imports("typing", {
+ "warnings",
+ "inspect",
+ "re",
+ "contextlib",
+ # "annotationlib", # TODO
+ })
+
@lru_cache()
def cached_func(x, y):
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