gh-150167: Force eager import of _bz2 in bz2.py to fix supported format detection

Doc/library/test.rst

@@ -1607,7 +1607,7 @@ The :mod:`!test.support.import_helper` module provides support for import tests.
    byte-compiled files of the module.
 
 
-.. function:: import_fresh_module(name, fresh=(), blocked=(), deprecated=False)
+.. function:: import_fresh_module(name, fresh=(), blocked=(), cleared=(), *, deprecated=False, usefrozen=False)
 
    This function imports and returns a fresh copy of the named Python module
    by removing the named module from ``sys.modules`` before doing the import.
@@ -1621,6 +1621,11 @@ The :mod:`!test.support.import_helper` module provides support for import tests.
    in the module cache during the import to ensure that attempts to import
    them raise :exc:`ImportError`.
 
+   *cleared* is an iterable of module names that are removed from the
+   sys.modules cache before doing the import but *are not* re-imported.
+   This is to allow for the case where these module imports may fail as part
+   of the test due to other modules that are blocked.
+
    The named module and any modules named in the *fresh* and *blocked*
    parameters are saved before starting the import and then reinserted into
    ``sys.modules`` when the fresh import is complete.
@@ -1631,6 +1636,9 @@ The :mod:`!test.support.import_helper` module provides support for import tests.
    This function will raise :exc:`ImportError` if the named module cannot be
    imported.
 
+   If "usefrozen" is False (the default) then the frozen importer is
+   disabled (except for essential modules like ``importlib._bootstrap``).
+
    Example use::
 
       # Get copies of the warnings module for testing without affecting the
@@ -1641,6 +1649,8 @@ The :mod:`!test.support.import_helper` module provides support for import tests.
       c_warnings = import_fresh_module('warnings', fresh=['_warnings'])
 
    .. versionadded:: 3.1
+   .. versionchanged:: next
+      New optional argument *cleared*.
 
 
 .. function:: import_module(name, deprecated=False, *, required_on=())

Lib/bz2.py

@@ -14,6 +14,9 @@
 import io
 import os
 
+# Force the eager import of _bz2
+# See: https://github.com/python/cpython/issues/150167
+import _bz2; _bz2
 from _bz2 import BZ2Compressor, BZ2Decompressor
 
 

Lib/test/support/import_helper.py

@@ -139,7 +139,7 @@ def multi_interp_extensions_check(enabled=True):
         _imp._override_multi_interp_extensions_check(old)
 
 
-def import_fresh_module(name, fresh=(), blocked=(), *,
+def import_fresh_module(name, fresh=(), blocked=(), cleared=(), *,
                         deprecated=False,
                         usefrozen=False,
                         ):
@@ -158,7 +158,12 @@ def import_fresh_module(name, fresh=(), blocked=(), *,
     in the module cache during the import to ensure that attempts to import
     them raise ImportError.
 
-    The named module and any modules named in the *fresh* and *blocked*
+    *cleared* is an iterable of module names that are removed from the
+    sys.modules cache before doing the import but *are not* re-imported.
+    This is to allow for the case where these module imports may fail as part
+    of the test due to other modules that are blocked.
+
+    The named module and any modules named in the *fresh*, *blocked* and *cleared*
     parameters are saved before starting the import and then reinserted into
     sys.modules when the fresh import is complete.
 
@@ -178,7 +183,8 @@ def import_fresh_module(name, fresh=(), blocked=(), *,
         # as those which just need a blocking entry removed
         fresh = list(fresh)
         blocked = list(blocked)
-        names = {name, *fresh, *blocked}
+        cleared = list(cleared)
+        names = {name, *fresh, *blocked, *cleared}
         orig_modules = _save_and_remove_modules(names)
         for modname in blocked:
             sys.modules[modname] = None

Lib/test/test_shutil.py

@@ -32,6 +32,7 @@
 from test import support
 from test.support import os_helper, socket_helper
 from test.support.os_helper import TESTFN, FakePath
+from test.support.import_helper import import_fresh_module
 
 TESTFN2 = TESTFN + "2"
 TESTFN_SRC = TESTFN + "_SRC"
@@ -2322,6 +2323,75 @@ def _boo(filename, extract_dir, extra):
         self.assertEqual(get_unpack_formats(), formats)
 
 
+@support.requires_bz2()
+@support.requires_lzma()
+@support.requires_zlib()
+@support.requires_zstd()
+class TestLazyArchiveDetection(unittest.TestCase):
+    # Test archive detection under 'all' lazy imports
+    # see: https://github.com/python/cpython/issues/150167
+    @support.thread_unsafe("Modifies global import state")
+    def test_lazy_success(self):
+        import_state = sys.get_lazy_imports()
+        try:
+            sys.set_lazy_imports("all")
+            lazy_shutil = import_fresh_module(
+                "shutil",
+                cleared=(
+                    "bz2",
+                    "lzma",
+                    "zlib",
+                    "compression",
+                    "compression.zstd",
+                    "_bz2",
+                    "_lzma",
+                    "_zstd",
+                ),
+            )
+        finally:
+            sys.set_lazy_imports(import_state)
+
+        assert lazy_shutil is not None  # type narrowing
+
+        formats = {
+            "bz2": lazy_shutil._BZ2_SUPPORTED,
+            "lzma": lazy_shutil._LZMA_SUPPORTED,
+            "zlib": lazy_shutil._ZLIB_SUPPORTED,
+            "zstd": lazy_shutil._ZSTD_SUPPORTED,
+        }
+
+        expected = {k: True for k in formats}
+
+        self.assertEqual(formats, expected)
+
+
+    @support.thread_unsafe("Modifies global import state")
+    def test_lazy_failure(self):
+        import_state = sys.get_lazy_imports()
+        try:
+            sys.set_lazy_imports("all")
+            lazy_shutil = import_fresh_module(
+                "shutil",
+                blocked=("_bz2", "_lzma", "zlib", "_zstd"),
+                cleared=("bz2", "lzma", "compression", "compression.zstd"),
+            )
+        finally:
+            sys.set_lazy_imports(import_state)
+
+        assert lazy_shutil is not None  # type narrowing
+
+        formats = {
+            "bz2": lazy_shutil._BZ2_SUPPORTED,
+            "lzma": lazy_shutil._LZMA_SUPPORTED,
+            "zlib": lazy_shutil._ZLIB_SUPPORTED,
+            "zstd": lazy_shutil._ZSTD_SUPPORTED,
+        }
+
+        expected = {k: False for k in formats}
+
+        self.assertEqual(formats, expected)
+
+
 class TestMisc(BaseTest, unittest.TestCase):
 
     @unittest.skipUnless(hasattr(shutil, 'disk_usage'),