gh-91246: Implement PEP 775: Make zlib required on platforms other than wasi

Lib/shutil.py

@@ -11,12 +11,6 @@
 import collections
 import errno
 
-try:
-    import zlib
-    del zlib
-    _ZLIB_SUPPORTED = True
-except ImportError:
-    _ZLIB_SUPPORTED = False
 
 try:
     import bz2
@@ -1000,7 +994,7 @@ def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
     """
     if compress is None:
         tar_compression = ''
-    elif _ZLIB_SUPPORTED and compress == 'gzip':
+    elif compress == 'gzip':
         tar_compression = 'gz'
     elif _BZ2_SUPPORTED and compress == 'bzip2':
         tar_compression = 'bz2'
@@ -1121,10 +1115,9 @@ def _make_zipfile(base_name, base_dir, verbose=0, dry_run=0,
               "uncompressed tar file"),
 }
 
-if _ZLIB_SUPPORTED:
-    _ARCHIVE_FORMATS['gztar'] = (_make_tarball, [('compress', 'gzip')],
-                                "gzip'ed tar-file")
-    _ARCHIVE_FORMATS['zip'] = (_make_zipfile, [], "ZIP file")
+_ARCHIVE_FORMATS['gztar'] = (_make_tarball, [('compress', 'gzip')],
+                            "gzip'ed tar-file")
+_ARCHIVE_FORMATS['zip'] = (_make_zipfile, [], "ZIP file")
 
 if _BZ2_SUPPORTED:
     _ARCHIVE_FORMATS['bztar'] = (_make_tarball, [('compress', 'bzip2')],
@@ -1345,12 +1338,9 @@ def _unpack_tarfile(filename, extract_dir, *, filter=None):
 _UNPACK_FORMATS = {
     'tar':   (['.tar'], _unpack_tarfile, [], "uncompressed tar file"),
     'zip':   (['.zip'], _unpack_zipfile, [], "ZIP file"),
+    'gztar': (['.tar.gz', '.tgz'], _unpack_tarfile, [], "gzip'ed tar-file"),
 }
 
-if _ZLIB_SUPPORTED:
-    _UNPACK_FORMATS['gztar'] = (['.tar.gz', '.tgz'], _unpack_tarfile, [],
-                                "gzip'ed tar-file")
-
 if _BZ2_SUPPORTED:
     _UNPACK_FORMATS['bztar'] = (['.tar.bz2', '.tbz2'], _unpack_tarfile, [],
                                 "bzip2'ed tar-file")

Lib/tarfile.py

@@ -364,10 +364,7 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
 
         try:
             if comptype == "gz":
-                try:
-                    import zlib
-                except ImportError:
-                    raise CompressionError("zlib module is not available") from None
+                import zlib
                 self.zlib = zlib
                 self.crc = zlib.crc32(b"")
                 if mode == "r":
@@ -2697,13 +2694,10 @@ def next(self):
             except SubsequentHeaderError as e:
                 raise ReadError(str(e)) from None
             except Exception as e:
-                try:
-                    import zlib
-                    if isinstance(e, zlib.error):
-                        raise ReadError(f'zlib error: {e}') from None
-                    else:
-                        raise e
-                except ImportError:
+                import zlib
+                if isinstance(e, zlib.error):
+                    raise ReadError(f'zlib error: {e}') from None
+                else:
                     raise e
             break
 

Lib/zipfile/__init__.py

@@ -14,12 +14,8 @@
 import threading
 import time
 
-try:
-    import zlib # We may need its compression method
-    crc32 = zlib.crc32
-except ImportError:
-    zlib = None
-    crc32 = binascii.crc32
+import zlib
+crc32 = zlib.crc32
 
 try:
     import bz2 # We may need its compression method
@@ -771,12 +767,8 @@ def decompress(self, data):
 }
 
 def _check_compression(compression):
-    if compression == ZIP_STORED:
+    if compression in (ZIP_STORED, ZIP_DEFLATED):
         pass
-    elif compression == ZIP_DEFLATED:
-        if not zlib:
-            raise RuntimeError(
-                "Compression requires the (missing) zlib module")
     elif compression == ZIP_BZIP2:
         if not bz2:
             raise RuntimeError(

Lib/zipimport.py

@@ -604,9 +604,7 @@ def _read_directory(archive):
 
 _importing_zlib = False
 
-# Return the zlib.decompress function object, or NULL if zlib couldn't
-# be imported. The function is cached when found, so subsequent calls
-# don't import zlib again.
+# Return the zlib.decompress function object or raise an import error.
 def _get_decompress_func():
     global _importing_zlib
     if _importing_zlib:
@@ -618,9 +616,6 @@ def _get_decompress_func():
     _importing_zlib = True
     try:
         from zlib import decompress
-    except Exception:
-        _bootstrap._verbose_message('zipimport: zlib UNAVAILABLE')
-        raise ZipImportError("can't decompress data; zlib not available")
     finally:
         _importing_zlib = False