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"""Tests for PEP 810 lazy imports."""
import io
import dis
import subprocess
import sys
import textwrap
import threading
import types
import unittest
import tempfile
import os
try:
import _testcapi
except ImportError:
_testcapi = None
class LazyImportTests(unittest.TestCase):
"""Tests for basic lazy import functionality."""
def tearDown(self):
"""Clean up any test modules from sys.modules."""
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
sys.lazy_modules.clear()
def test_basic_unused(self):
"""Lazy imported module should not be loaded if never accessed."""
import test.test_import.data.lazy_imports.basic_unused
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
self.assertIn("test.test_import.data.lazy_imports", sys.lazy_modules)
self.assertEqual(sys.lazy_modules["test.test_import.data.lazy_imports"], {"basic2"})
def test_sys_lazy_modules(self):
try:
import test.test_import.data.lazy_imports.basic_from_unused
except ImportError as e:
self.fail('lazy import failed')
self.assertFalse("test.test_import.data.lazy_imports.basic2" in sys.modules)
self.assertIn("test.test_import.data.lazy_imports", sys.lazy_modules)
self.assertEqual(sys.lazy_modules["test.test_import.data.lazy_imports"], {"basic2"})
test.test_import.data.lazy_imports.basic_from_unused.basic2
self.assertNotIn("test.test_import.data", sys.lazy_modules)
def test_basic_unused_use_externally(self):
"""Lazy import should load module when accessed from outside."""
from test.test_import.data.lazy_imports import basic_unused
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
x = basic_unused.test.test_import.data.lazy_imports.basic2
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_basic_from_unused_use_externally(self):
"""Lazy 'from' import should load when accessed from outside."""
from test.test_import.data.lazy_imports import basic_from_unused
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
x = basic_from_unused.basic2
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_basic_unused_dir(self):
"""dir() on module should not trigger lazy import reification."""
import test.test_import.data.lazy_imports.basic_unused
x = dir(test.test_import.data.lazy_imports.basic_unused)
self.assertIn("test", x)
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_basic_dir(self):
"""dir() at module scope should not trigger lazy import reification."""
from test.test_import.data.lazy_imports import basic_dir
self.assertIn("test", basic_dir.x)
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_basic_used(self):
"""Lazy import should load when accessed within the module."""
import test.test_import.data.lazy_imports.basic_used
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
class GlobalLazyImportModeTests(unittest.TestCase):
"""Tests for sys.set_lazy_imports() global mode control."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_global_off(self):
"""Mode 'none' should disable lazy imports entirely."""
import test.test_import.data.lazy_imports.global_off
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_global_on(self):
"""Mode 'all' should make regular imports lazy."""
import test.test_import.data.lazy_imports.global_on
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_global_filter(self):
"""Filter returning False should prevent lazy loading."""
import test.test_import.data.lazy_imports.global_filter
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_global_filter_true(self):
"""Filter returning True should allow lazy loading."""
import test.test_import.data.lazy_imports.global_filter_true
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_global_filter_from(self):
"""Filter should work with 'from' imports."""
import test.test_import.data.lazy_imports.global_filter
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_global_filter_from_true(self):
"""Filter returning True should allow lazy 'from' imports."""
import test.test_import.data.lazy_imports.global_filter_true
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
class CompatibilityModeTests(unittest.TestCase):
"""Tests for __lazy_modules__ compatibility mode."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_compatibility_mode(self):
"""__lazy_modules__ should enable lazy imports for listed modules."""
import test.test_import.data.lazy_imports.basic_compatibility_mode
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_compatibility_mode_used(self):
"""Using a lazy import from __lazy_modules__ should load the module."""
import test.test_import.data.lazy_imports.basic_compatibility_mode_used
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_compatibility_mode_func(self):
"""Imports inside functions should be eager even in compatibility mode."""
import test.test_import.data.lazy_imports.compatibility_mode_func
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_compatibility_mode_try_except(self):
"""Imports in try/except should be eager even in compatibility mode."""
import test.test_import.data.lazy_imports.compatibility_mode_try_except
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_compatibility_mode_relative(self):
"""__lazy_modules__ should work with relative imports."""
import test.test_import.data.lazy_imports.basic_compatibility_mode_relative
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
class ModuleIntrospectionTests(unittest.TestCase):
"""Tests for module dict and getattr behavior with lazy imports."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_modules_dict(self):
"""Accessing module.__dict__ should not trigger reification."""
import test.test_import.data.lazy_imports.modules_dict
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_modules_getattr(self):
"""Module __getattr__ for lazy import name should trigger reification."""
import test.test_import.data.lazy_imports.modules_getattr
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_modules_getattr_other(self):
"""Module __getattr__ for other names should not trigger reification."""
import test.test_import.data.lazy_imports.modules_getattr_other
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
class LazyImportTypeTests(unittest.TestCase):
"""Tests for the LazyImportType and its resolve() method."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_lazy_value_resolve(self):
"""resolve() method should force the lazy import to load."""
import test.test_import.data.lazy_imports.lazy_get_value
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_lazy_import_type_exposed(self):
"""LazyImportType should be exposed in types module."""
self.assertHasAttr(types, 'LazyImportType')
self.assertEqual(types.LazyImportType.__name__, 'lazy_import')
def test_lazy_import_type_cant_construct(self):
"""LazyImportType should not be directly constructible."""
self.assertRaises(TypeError, types.LazyImportType, {}, "module")
class SyntaxRestrictionTests(unittest.TestCase):
"""Tests for syntax restrictions on lazy imports."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_lazy_try_except(self):
"""lazy import inside try/except should raise SyntaxError."""
with self.assertRaises(SyntaxError):
import test.test_import.data.lazy_imports.lazy_try_except
def test_lazy_try_except_from(self):
"""lazy from import inside try/except should raise SyntaxError."""
with self.assertRaises(SyntaxError):
import test.test_import.data.lazy_imports.lazy_try_except_from
def test_lazy_try_except_from_star(self):
"""lazy from import * should raise SyntaxError."""
with self.assertRaises(SyntaxError):
import test.test_import.data.lazy_imports.lazy_try_except_from_star
def test_lazy_future_import(self):
"""lazy from __future__ import should raise SyntaxError."""
with self.assertRaises(SyntaxError) as cm:
import test.test_import.data.lazy_imports.lazy_future_import
# Check we highlight 'lazy' (column offset 0, end offset 4)
self.assertEqual(cm.exception.offset, 1)
self.assertEqual(cm.exception.end_offset, 5)
def test_lazy_import_func(self):
"""lazy import inside function should raise SyntaxError."""
with self.assertRaises(SyntaxError):
import test.test_import.data.lazy_imports.lazy_import_func
def test_lazy_import_exec_in_function(self):
"""lazy import via exec() inside a function should raise SyntaxError."""
# exec() inside a function creates a non-module-level context
# where lazy imports are not allowed
def f():
exec("lazy import json")
with self.assertRaises(SyntaxError) as cm:
f()
self.assertIn("only allowed at module level", str(cm.exception))
def test_lazy_import_exec_at_module_level(self):
"""lazy import via exec() at module level should work."""
# exec() at module level (globals == locals) should allow lazy imports
code = textwrap.dedent("""
import sys
exec("lazy import json")
# Should be lazy - not loaded yet
assert 'json' not in sys.modules
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
class EagerImportInLazyModeTests(unittest.TestCase):
"""Tests for imports that should remain eager even in lazy mode."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_try_except_eager(self):
"""Imports in try/except should be eager even with mode='all'."""
sys.set_lazy_imports("all")
import test.test_import.data.lazy_imports.try_except_eager
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_try_except_eager_from(self):
"""From imports in try/except should be eager even with mode='all'."""
sys.set_lazy_imports("all")
import test.test_import.data.lazy_imports.try_except_eager_from
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_eager_import_func(self):
"""Imports inside functions should return modules, not proxies."""
sys.set_lazy_imports("all")
import test.test_import.data.lazy_imports.eager_import_func
f = test.test_import.data.lazy_imports.eager_import_func.f
self.assertEqual(type(f()), type(sys))
class WithStatementTests(unittest.TestCase):
"""Tests for lazy imports in with statement context."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_lazy_with(self):
"""lazy import with 'with' statement should work."""
import test.test_import.data.lazy_imports.lazy_with
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_lazy_with_from(self):
"""lazy from import with 'with' statement should work."""
import test.test_import.data.lazy_imports.lazy_with_from
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
class PackageTests(unittest.TestCase):
"""Tests for lazy imports with packages."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_lazy_import_pkg(self):
"""lazy import of package submodule should load the package."""
import test.test_import.data.lazy_imports.lazy_import_pkg
self.assertIn("test.test_import.data.lazy_imports.pkg", sys.modules)
self.assertIn("test.test_import.data.lazy_imports.pkg.bar", sys.modules)
def test_lazy_import_pkg_cross_import(self):
"""Cross-imports within package should preserve lazy imports."""
import test.test_import.data.lazy_imports.pkg.c
self.assertIn("test.test_import.data.lazy_imports.pkg", sys.modules)
self.assertIn("test.test_import.data.lazy_imports.pkg.c", sys.modules)
self.assertNotIn("test.test_import.data.lazy_imports.pkg.b", sys.modules)
g = test.test_import.data.lazy_imports.pkg.c.get_globals()
self.assertEqual(type(g["x"]), int)
self.assertEqual(type(g["b"]), types.LazyImportType)
class DunderLazyImportTests(unittest.TestCase):
"""Tests for __lazy_import__ builtin function."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_dunder_lazy_import(self):
"""__lazy_import__ should create lazy import proxy."""
import test.test_import.data.lazy_imports.dunder_lazy_import
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_dunder_lazy_import_used(self):
"""Using __lazy_import__ result should trigger module load."""
import test.test_import.data.lazy_imports.dunder_lazy_import_used
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_dunder_lazy_import_builtins(self):
"""__lazy_import__ should use module's __builtins__ for __import__."""
from test.test_import.data.lazy_imports import dunder_lazy_import_builtins
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
self.assertEqual(dunder_lazy_import_builtins.basic.basic2, 42)
class SysLazyImportsAPITests(unittest.TestCase):
"""Tests for sys lazy imports API functions."""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_set_lazy_imports_requires_string(self):
"""set_lazy_imports should reject non-string arguments."""
with self.assertRaises(TypeError):
sys.set_lazy_imports(True)
with self.assertRaises(TypeError):
sys.set_lazy_imports(None)
with self.assertRaises(TypeError):
sys.set_lazy_imports(1)
def test_set_lazy_imports_rejects_invalid_mode(self):
"""set_lazy_imports should reject invalid mode strings."""
with self.assertRaises(ValueError):
sys.set_lazy_imports("invalid")
with self.assertRaises(ValueError):
sys.set_lazy_imports("on")
with self.assertRaises(ValueError):
sys.set_lazy_imports("off")
def test_get_lazy_imports_returns_string(self):
"""get_lazy_imports should return string modes."""
sys.set_lazy_imports("normal")
self.assertEqual(sys.get_lazy_imports(), "normal")
sys.set_lazy_imports("all")
self.assertEqual(sys.get_lazy_imports(), "all")
sys.set_lazy_imports("none")
self.assertEqual(sys.get_lazy_imports(), "none")
def test_get_lazy_imports_filter_default(self):
"""get_lazy_imports_filter should return None by default."""
sys.set_lazy_imports_filter(None)
self.assertIsNone(sys.get_lazy_imports_filter())
def test_set_and_get_lazy_imports_filter(self):
"""set/get_lazy_imports_filter should round-trip filter function."""
def my_filter(name):
return name.startswith("test.")
sys.set_lazy_imports_filter(my_filter)
self.assertIs(sys.get_lazy_imports_filter(), my_filter)
def test_lazy_modules_attribute_is_set(self):
"""sys.lazy_modules should be a set per PEP 810."""
self.assertIsInstance(sys.lazy_modules, dict)
def test_lazy_modules_tracks_lazy_imports(self):
"""sys.lazy_modules should track lazily imported module names."""
code = textwrap.dedent("""
import sys
initial_count = len(sys.lazy_modules)
import test.test_import.data.lazy_imports.basic_unused
assert "test.test_import.data.lazy_imports" in sys.lazy_modules
assert sys.lazy_modules["test.test_import.data.lazy_imports"] == {"basic2"}
assert len(sys.lazy_modules) > initial_count
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
class ErrorHandlingTests(unittest.TestCase):
"""Tests for error handling during lazy import reification.
PEP 810: Errors during reification should show exception chaining with
both the lazy import definition location and the access location.
"""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_import_error_shows_chained_traceback(self):
"""ImportError during reification should chain to show both definition and access."""
# Errors at reification must show where the lazy import was defined
# AND where the access happened, per PEP 810 "Reification" section
code = textwrap.dedent("""
import sys
lazy import test.test_import.data.lazy_imports.nonexistent_module
try:
x = test.test_import.data.lazy_imports.nonexistent_module
except ImportError as e:
# Should have __cause__ showing the original error
# The exception chain shows both where import was defined and where access happened
assert e.__cause__ is not None, "Expected chained exception"
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_attribute_error_on_from_import_shows_chained_traceback(self):
"""Accessing missing attribute from lazy from-import should chain errors."""
# Tests 'lazy from module import nonexistent' behavior
code = textwrap.dedent("""
import sys
lazy from test.test_import.data.lazy_imports.basic2 import nonexistent_name
try:
x = nonexistent_name
except ImportError as e:
# PEP 810: Enhanced error reporting through exception chaining
assert e.__cause__ is not None, "Expected chained exception"
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_reification_retries_on_failure(self):
"""Failed reification should allow retry on subsequent access.
PEP 810: "If reification fails, the lazy object is not reified or replaced.
Subsequent uses of the lazy object will re-try the reification."
"""
code = textwrap.dedent("""
import sys
import types
lazy import test.test_import.data.lazy_imports.broken_module
# First access - should fail
try:
x = test.test_import.data.lazy_imports.broken_module
except ValueError:
pass
# The lazy object should still be a lazy proxy (not reified)
g = globals()
lazy_obj = g['test']
# The root 'test' binding should still allow retry
# Second access - should also fail (retry the import)
try:
x = test.test_import.data.lazy_imports.broken_module
except ValueError:
print("OK - retry worked")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_error_during_module_execution_propagates(self):
"""Errors in module code during reification should propagate correctly."""
# Module that raises during import should propagate with chaining
code = textwrap.dedent("""
import sys
lazy import test.test_import.data.lazy_imports.broken_module
try:
_ = test.test_import.data.lazy_imports.broken_module
print("FAIL - should have raised")
except ValueError as e:
# The ValueError from the module should be the cause
if "always fails" in str(e) or (e.__cause__ and "always fails" in str(e.__cause__)):
print("OK")
else:
print(f"FAIL - wrong error: {e}")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_circular_lazy_import_does_not_crash_for_gh_144727(self):
with tempfile.TemporaryDirectory() as tmpdir:
a_path = os.path.join(tmpdir, "a.py")
b_path = os.path.join(tmpdir, "b.py")
with open(a_path, "w") as f:
f.write(textwrap.dedent("""\
lazy import b
def something():
b.hello()
something()
"""))
with open(b_path, "w") as f:
f.write(textwrap.dedent("""\
lazy import a
def hello():
print(a)
"""))
result = subprocess.run(
[sys.executable, a_path],
capture_output=True,
text=True,
cwd=tmpdir,
)
# Should get a proper Python error, not a crash
self.assertEqual(result.returncode, 1)
self.assertIn("Error", result.stderr)
class GlobalsAndDictTests(unittest.TestCase):
"""Tests for globals() and __dict__ behavior with lazy imports.
PEP 810: "Calling globals() or accessing a module's __dict__ does not trigger
reification – they return the module's dictionary, and accessing lazy objects
through that dictionary still returns lazy proxy objects."
"""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_globals_returns_lazy_proxy_when_accessed_from_function(self):
"""globals() accessed from a function should return lazy proxy without reification.
Note: At module level, accessing globals()['name'] triggers LOAD_NAME which
automatically resolves lazy imports. Inside a function, accessing globals()['name']
uses BINARY_SUBSCR which returns the lazy proxy without resolution.
"""
code = textwrap.dedent("""
import sys
import types
lazy from test.test_import.data.lazy_imports.basic2 import x
# Check that module is not yet loaded
assert 'test.test_import.data.lazy_imports.basic2' not in sys.modules
def check_lazy():
# Access through globals() from inside a function
g = globals()
lazy_obj = g['x']
return type(lazy_obj) is types.LazyImportType
# Inside function, should get lazy proxy
is_lazy = check_lazy()
assert is_lazy, "Expected LazyImportType from function scope"
# Module should STILL not be loaded
assert 'test.test_import.data.lazy_imports.basic2' not in sys.modules
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_globals_dict_access_returns_lazy_proxy_inline(self):
"""Accessing globals()['name'] inline should return lazy proxy.
Note: Assigning g['name'] to a local variable at module level triggers
reification due to STORE_NAME bytecode. Inline access preserves laziness.
"""
code = textwrap.dedent("""
import sys
import types
lazy import json
# Inline access without assignment to local variable preserves lazy proxy
assert type(globals()['json']) is types.LazyImportType
assert 'json' not in sys.modules
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_module_dict_returns_lazy_proxy_without_reifying(self):
"""module.__dict__ access should not trigger reification."""
import test.test_import.data.lazy_imports.globals_access
# Module not loaded yet via direct dict access
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
# Access via get_from_globals should return lazy proxy
lazy_obj = test.test_import.data.lazy_imports.globals_access.get_from_globals()
self.assertEqual(type(lazy_obj), types.LazyImportType)
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_direct_access_triggers_reification(self):
"""Direct name access (not through globals()) should trigger reification."""
import test.test_import.data.lazy_imports.globals_access
self.assertNotIn("test.test_import.data.lazy_imports.basic2", sys.modules)
# Direct access should reify
result = test.test_import.data.lazy_imports.globals_access.get_direct()
self.assertIn("test.test_import.data.lazy_imports.basic2", sys.modules)
def test_resolve_method_forces_reification(self):
"""Calling resolve() on lazy proxy should force reification.
Note: Must access lazy proxy from within a function to avoid automatic
reification by LOAD_NAME at module level.
"""
code = textwrap.dedent("""
import sys
import types
lazy from test.test_import.data.lazy_imports.basic2 import x
assert 'test.test_import.data.lazy_imports.basic2' not in sys.modules
def test_resolve():
g = globals()
lazy_obj = g['x']
assert type(lazy_obj) is types.LazyImportType, f"Expected lazy proxy, got {type(lazy_obj)}"
resolved = lazy_obj.resolve()
# Now module should be loaded
assert 'test.test_import.data.lazy_imports.basic2' in sys.modules
assert resolved == 42 # x is 42 in basic2.py
return True
assert test_resolve()
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_add_lazy_to_globals(self):
code = textwrap.dedent("""
import sys
import types
lazy from test.test_import.data.lazy_imports import basic2
assert 'test.test_import.data.lazy_imports.basic2' not in sys.modules
class C: pass
sneaky = C()
sneaky.x = 1
def f():
t = 0
for _ in range(5):
t += sneaky.x
return t
f()
globals()["sneaky"] = globals()["basic2"]
assert f() == 210
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
class MultipleNameFromImportTests(unittest.TestCase):
"""Tests for lazy from ... import with multiple names.
PEP 810: "When using lazy from ... import, each imported name is bound to a
lazy proxy object. The first access to any of these names triggers loading
of the entire module and reifies only that specific name to its actual value.
Other names remain as lazy proxies until they are accessed."
"""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_accessing_one_name_leaves_others_as_proxies(self):
"""Accessing one name from multi-name import should leave others lazy."""
code = textwrap.dedent("""
import sys
import types
lazy from test.test_import.data.lazy_imports.basic2 import f, x
# Neither should be loaded yet
assert 'test.test_import.data.lazy_imports.basic2' not in sys.modules
g = globals()
assert type(g['f']) is types.LazyImportType
assert type(g['x']) is types.LazyImportType
# Access 'x' - this loads the module and reifies only 'x'
value = x
assert value == 42
# Module is now loaded
assert 'test.test_import.data.lazy_imports.basic2' in sys.modules
# 'x' should be reified (int), 'f' should still be lazy proxy
assert type(g['x']) is int, f"Expected int, got {type(g['x'])}"
assert type(g['f']) is types.LazyImportType, f"Expected LazyImportType, got {type(g['f'])}"
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_all_names_reified_after_all_accessed(self):
"""All names should be reified after each is accessed."""
code = textwrap.dedent("""
import sys
import types
lazy from test.test_import.data.lazy_imports.basic2 import f, x
g = globals()
# Access both
_ = x
_ = f
# Both should be reified now
assert type(g['x']) is int
assert callable(g['f'])
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
class SysLazyModulesTrackingTests(unittest.TestCase):
"""Tests for sys.lazy_modules tracking behavior.
PEP 810: "When the module is reified, it's removed from sys.lazy_modules"
"""
def tearDown(self):
for key in list(sys.modules.keys()):
if key.startswith('test.test_import.data.lazy_imports'):
del sys.modules[key]
sys.set_lazy_imports_filter(None)
sys.set_lazy_imports("normal")
def test_module_added_to_lazy_modules_on_lazy_import(self):
"""Module should be added to sys.lazy_modules when lazily imported."""
# PEP 810 states lazy_modules tracks modules that have been lazily imported
# Note: The current implementation keeps modules in lazy_modules even after
# reification (primarily for diagnostics and introspection)
code = textwrap.dedent("""
import sys
initial_count = len(sys.lazy_modules)
lazy import test.test_import.data.lazy_imports.basic2
# Should be in lazy_modules after lazy import
assert "test.test_import.data.lazy_imports" in sys.lazy_modules
assert sys.lazy_modules["test.test_import.data.lazy_imports"] == {"basic2"}
assert len(sys.lazy_modules) > initial_count
# Trigger reification
_ = test.test_import.data.lazy_imports.basic2.x
# Module should still be tracked (for diagnostics per PEP 810)
assert "test.test_import.data.lazy_imports" not in sys.lazy_modules
print("OK")
""")
result = subprocess.run(
[sys.executable, "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
self.assertIn("OK", result.stdout)
def test_lazy_modules_is_per_interpreter(self):
"""Each interpreter should have independent sys.lazy_modules."""
# Basic test that sys.lazy_modules exists and is a set
self.assertIsInstance(sys.lazy_modules, dict)
class CommandLineAndEnvVarTests(unittest.TestCase):
"""Tests for command-line and environment variable control.
PEP 810: The global lazy imports flag can be controlled through:
- The -X lazy_imports=<mode> command-line option
- The PYTHON_LAZY_IMPORTS=<mode> environment variable
"""
def test_cli_lazy_imports_all_makes_regular_imports_lazy(self):
"""-X lazy_imports=all should make all imports potentially lazy."""
code = textwrap.dedent("""
import sys
# In 'all' mode, regular imports become lazy
import json
# json should not be in sys.modules yet (lazy)
# Actually accessing it triggers reification
if 'json' not in sys.modules:
print("LAZY")
else:
print("EAGER")
""")
result = subprocess.run(
[sys.executable, "-X", "lazy_imports=all", "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
self.assertIn("LAZY", result.stdout)
def test_cli_lazy_imports_none_forces_all_imports_eager(self):
"""-X lazy_imports=none should force all imports to be eager."""
code = textwrap.dedent("""
import sys
# Even explicit lazy imports should be eager in 'none' mode
lazy import json
if 'json' in sys.modules:
print("EAGER")
else:
print("LAZY")
""")
result = subprocess.run(
[sys.executable, "-X", "lazy_imports=none", "-c", code],
capture_output=True,
text=True
)
self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
self.assertIn("EAGER", result.stdout)
def test_cli_lazy_imports_normal_respects_lazy_keyword_only(self):
"""-X lazy_imports=normal should respect lazy keyword only."""
# Note: Use test modules instead of stdlib modules to avoid
# modules already loaded by the interpreter startup
code = textwrap.dedent("""
import sys
import test.test_import.data.lazy_imports.basic2 # Should be eager
lazy import test.test_import.data.lazy_imports.pkg.b # Should be lazy
eager_loaded = 'test.test_import.data.lazy_imports.basic2' in sys.modules
lazy_loaded = 'test.test_import.data.lazy_imports.pkg.b' in sys.modules
if eager_loaded and not lazy_loaded:
print("OK")
else: