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gh-150167: Make shutil compression probes eager #150279

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RaghunandanKumar wants to merge 1 commit into from
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gh-150167: Make shutil compression probes eager #150279

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49 changes: 22 additions & 27 deletions Lib/shutil.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,34 +10,29 @@
import fnmatch
import collections
import errno
import importlib

try:
import zlib
del zlib
_ZLIB_SUPPORTED = True
except ImportError:
_ZLIB_SUPPORTED = False

try:
import bz2
del bz2
_BZ2_SUPPORTED = True
except ImportError:
_BZ2_SUPPORTED = False

try:
import lzma
del lzma
_LZMA_SUPPORTED = True
except ImportError:
_LZMA_SUPPORTED = False

try:
from compression import zstd
del zstd
_ZSTD_SUPPORTED = True
except ImportError:
_ZSTD_SUPPORTED = False
def _compression_module_supported(module_name):
set_lazy_imports = getattr(sys, "set_lazy_imports", None)
try:
if set_lazy_imports is None:
importlib.import_module(module_name)
return True

lazy_imports_mode = sys.get_lazy_imports()
set_lazy_imports("normal")
importlib.import_module(module_name)
except ImportError:
return False
finally:
if set_lazy_imports is not None:
set_lazy_imports(lazy_imports_mode)
return True

_ZLIB_SUPPORTED = _compression_module_supported("zlib")
_BZ2_SUPPORTED = _compression_module_supported("bz2")
_LZMA_SUPPORTED = _compression_module_supported("lzma")
_ZSTD_SUPPORTED = _compression_module_supported("compression.zstd")

_WINDOWS = os.name == 'nt'
posix = nt = None
Expand Down
22 changes: 22 additions & 0 deletions Lib/test/test_shutil.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
from test import support
from test.support import os_helper
from test.support.os_helper import TESTFN, FakePath
from test.support.script_helper import assert_python_ok

TESTFN2 = TESTFN + "2"
TESTFN_SRC = TESTFN + "_SRC"
Expand Down Expand Up @@ -2177,6 +2178,27 @@ def test_unpack_archive_gztar(self):
def test_unpack_archive_bztar(self):
self.check_unpack_tarball('bztar')

@support.requires_subprocess()
def test_bz2_support_probe_is_eager_under_lazy_imports(self):
module_dir = self.mkdtemp()
create_file(
(module_dir, 'bz2.py'),
'import _bz2\n'
'SENTINEL = True\n',
)
create_file(
(module_dir, '_bz2.py'),
'raise ImportError("missing _bz2 backend")\n',
)
code = f"""
import sys
sys.path.insert(0, {module_dir!r})
import shutil
print(shutil._BZ2_SUPPORTED)
"""
proc = assert_python_ok('-X', 'lazy_imports=all', '-S', '-c', code)
self.assertEqual(proc.out.strip(), b'False')

@support.requires_zstd()
def test_unpack_archive_zstdtar(self):
self.check_unpack_tarball('zstdtar')
Expand Down
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-05-22-18-40-00.gh-issue-150167.5L9x2h.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Make :mod:`shutil` probe compression-module support eagerly even when Python is
started with ``-X lazy_imports=all``. This fixes cases where
``shutil._BZ2_SUPPORTED`` could be reported as ``True`` even though the
underlying ``_bz2`` extension is unavailable.
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