fix: accept any readable file-like object in convert_to_bytes()

[weiguangli-o]

Closes #4097

Problem

When a user opens a file from inside a zip archive via zipfile.ZipFile.open() and passes the resulting ZipExtFile into partition(), the call crashes with:

ValueError: Invalid file-like object type

This happens because convert_to_bytes() only accepts a hardcoded whitelist of types (BytesIO, BufferedReader, SpooledTemporaryFile, TextIOWrapper). Any other IO[bytes] implementation — including ZipExtFile — is immediately rejected.

Fix

Added a duck-typing fallback before the final raise ValueError(...): if the object has a .read() method, read it; if it also has .seek(), reset the cursor so the caller can re-read the file. This preserves all existing behavior for the whitelisted types while also covering ZipExtFile, GzipFile, tarfile.ExFileObject, and any other standard IO[bytes] implementation.

Testing

Four new unit tests added in test_unstructured/partition/common/test_common.py:

Test	Verifies
it_reads_a_ZipExtFile	ZipExtFile from a zip archive is accepted and returns correct bytes
it_resets_cursor_after_reading_a_ZipExtFile	File cursor is reset so the caller can re-read
it_reads_a_generic_IO_bytes_with_read_method	Any object with .read() is accepted (duck-typing)
it_raises_on_a_non_readable_object	Non-file objects still raise ValueError

To verify locally:

import zipfile
from io import BytesIO
from unstructured.partition.common.common import convert_to_bytes

buf = BytesIO()
with zipfile.ZipFile(buf, "w") as zf:
    zf.writestr("hello.txt", b"Hello from zip!")
buf.seek(0)

with zipfile.ZipFile(buf) as zf:
    with zf.open("hello.txt") as f:
        print(convert_to_bytes(f))  # b'Hello from zip!'

[weiguangli-o]

Closing — shifting focus to AI Agent core projects. Thank you for your time!