gh-123424: add ZipInfo._for_archive to set suitable default properties

Doc/library/zipfile.rst

@@ -84,6 +84,18 @@ The module defines the following items:
       formerly protected :attr:`!_compresslevel`.  The older protected name
       continues to work as a property for backwards compatibility.
 
+
+   .. classmethod:: for_name(filename, archive, *, date_time=None)
+
+      Construct an appropriate :class:`ZipInfo` from a *filename*,
+      a :class:`ZipFile` archive and an optional *date_time*.
+
+      If *date_time* is not specified, the current local time is used
+      instead, namely ``date_time = time.localtime(time.time())[:6]``.
+
+      .. versionadded:: 3.14
+
+
 .. function:: is_zipfile(filename)
 
    Returns ``True`` if *filename* is a valid ZIP file based on its magic number,

Doc/whatsnew/3.14.rst

@@ -225,6 +225,16 @@ symtable
 
   (Contributed by Bénédikt Tran in :gh:`120029`.)
 
+
+zipinfo
+-------
+
+* Added :func:`ZipInfo.for_name <zipfile.ZipInfo.for_name>` for
+  constructing a :class:`~zipfile.ZipInfo` object from a filename
+  and an archive.
+
+  (Contributed by Bénédikt Tran in :gh:`123424`.)
+
 .. Add improved modules above alphabetically, not here at the end.
 
 Optimizations

Lib/test/test_zipfile/_path/test_path.py

@@ -657,20 +657,3 @@ class DirtyZipInfo(zipfile.ZipInfo):
     def __init__(self, filename, *args, **kwargs):
         super().__init__(filename, *args, **kwargs)
         self.filename = filename
-
-    @classmethod
-    def for_name(cls, name, archive):
-        """
-        Construct the same way that ZipFile.writestr does.
-
-        TODO: extract this functionality and re-use
-        """
-        self = cls(filename=name, date_time=time.localtime(time.time())[:6])
-        self.compress_type = archive.compression
-        self.compress_level = archive.compresslevel
-        if self.filename.endswith('/'):  # pragma: no cover
-            self.external_attr = 0o40775 << 16  # drwxrwxr-x
-            self.external_attr |= 0x10  # MS-DOS directory flag
-        else:
-            self.external_attr = 0o600 << 16  # ?rw-------
-        return self

Lib/test/test_zipfile/test_core.py

@@ -5,6 +5,7 @@
 import itertools
 import os
 import posixpath
+import stat
 import struct
 import subprocess
 import sys
@@ -2205,6 +2206,34 @@ def test_create_empty_zipinfo_repr(self):
         zi = zipfile.ZipInfo(filename="empty")
         self.assertEqual(repr(zi), "<ZipInfo filename='empty' file_size=0>")
 
+    def test_create_zipinfo_for_name(self):
+        base_filename = TESTFN2.rstrip('/')
+
+        with zipfile.ZipFile(TESTFN, mode="w", compresslevel=1,
+                             compression=zipfile.ZIP_STORED) as zf:
+            # no trailing forward slash
+            zi = zipfile.ZipInfo.for_name(base_filename, zf)
+            self.assertEqual(zi.compress_level, 1)
+            self.assertEqual(zi.compress_type, zipfile.ZIP_STORED)
+            # ?rw- --- ---
+            filemode = stat.S_IRUSR | stat.S_IWUSR
+            # filemode is stored as the highest 16 bits of external_attr
+            self.assertEqual(zi.external_attr >> 16, filemode)
+            self.assertEqual(zi.external_attr & 0xFF, 0)  # no MS-DOS flag
+
+        with zipfile.ZipFile(TESTFN, mode="w", compresslevel=1,
+                             compression=zipfile.ZIP_STORED) as zf:
+            # with a trailing slash
+            zi = zipfile.ZipInfo.for_name(f'{base_filename}/', zf)
+            self.assertEqual(zi.compress_level, 1)
+            self.assertEqual(zi.compress_type, zipfile.ZIP_STORED)
+            # d rwx rwx r-x
+            filemode = stat.S_IFDIR
+            filemode |= stat.S_IRWXU | stat.S_IRWXG
+            filemode |= stat.S_IROTH | stat.S_IXOTH
+            self.assertEqual(zi.external_attr >> 16, filemode)
+            self.assertEqual(zi.external_attr & 0xFF, 0x10)  # MS-DOS flag
+
     def test_create_empty_zipinfo_default_attributes(self):
         """Ensure all required attributes are set."""
         zi = zipfile.ZipInfo()

Lib/zipfile/__init__.py

@@ -603,6 +603,26 @@ def from_file(cls, filename, arcname=None, *, strict_timestamps=True):
 
         return zinfo
 
+    @classmethod
+    def for_name(cls, filename, archive, *, date_time=None):
+        """Construct an appropriate ZipInfo from a filename and a ZipFile.
+
+        The *filename* is expected to be the name of a file in the archive.
+
+        If *date_time* is not specified, the current local time is used.
+        """
+        if date_time is None:
+            date_time = time.localtime(time.time())[:6]
+        self = cls(filename=filename, date_time=date_time)
+        self.compress_type = archive.compression
+        self.compress_level = archive.compresslevel
+        if self.filename.endswith('/'):  # pragma: no cover
+            self.external_attr = 0o40775 << 16  # drwxrwxr-x
+            self.external_attr |= 0x10  # MS-DOS directory flag
+        else:
+            self.external_attr = 0o600 << 16  # ?rw-------
+        return self
+
     def is_dir(self):
         """Return True if this archive member is a directory."""
         if self.filename.endswith('/'):
@@ -1903,18 +1923,10 @@ def writestr(self, zinfo_or_arcname, data,
         the name of the file in the archive."""
         if isinstance(data, str):
             data = data.encode("utf-8")
-        if not isinstance(zinfo_or_arcname, ZipInfo):
-            zinfo = ZipInfo(filename=zinfo_or_arcname,
-                            date_time=time.localtime(time.time())[:6])
-            zinfo.compress_type = self.compression
-            zinfo.compress_level = self.compresslevel
-            if zinfo.filename.endswith('/'):
-                zinfo.external_attr = 0o40775 << 16   # drwxrwxr-x
-                zinfo.external_attr |= 0x10           # MS-DOS directory flag
-            else:
-                zinfo.external_attr = 0o600 << 16     # ?rw-------
-        else:
+        if isinstance(zinfo_or_arcname, ZipInfo):
             zinfo = zinfo_or_arcname
+        else:
+            zinfo = ZipInfo.for_name(zinfo_or_arcname, self)
 
         if not self.fp:
             raise ValueError(

Misc/NEWS.d/next/Library/2024-08-28-16-10-37.gh-issue-123424.u96_i6.rst

@@ -0,0 +1,3 @@
+Add :meth:`zipfile.ZipInfo.for_name` factory for constructing
+:class:`~zipfile.ZipInfo` objects from a filename and an archive. Patch by
+Bénédikt Tran.