fix: ZipConverter renders '(unknown)' instead of literal 'None' when stream has no source info (#2134)

* fix: ZipConverter emits '(unknown)' instead of 'None' when stream has no source info

When MarkItDown.convert_stream() is called with a ZIP stream that has no
associated URL, local_path, or filename (e.g. a raw io.BytesIO), the
ZipConverter header read:

    Content from the zip file `None`:

because stream_info.url, stream_info.local_path, and stream_info.filename
were all None and Python f-strings render None as the literal string 'None'.

Fix: fall back to '(unknown)' when all three source-info fields are absent,
producing the more descriptive:

    Content from the zip file `(unknown)`:

Add a regression test in test_module_misc.py that verifies the output does
not contain the literal string 'None' in this scenario.

* Fixed formatting.

---------

Co-authored-by: JSap0914 <JSap0914@users.noreply.github.com>
Co-authored-by: afourney <adamfo@microsoft.com>

Author: JSap0914

packages/markitdown/src/markitdown/converters/_zip_converter.py

@@ -90,7 +90,12 @@ def convert(
         stream_info: StreamInfo,
         **kwargs: Any,  # Options to pass to the converter
     ) -> DocumentConverterResult:
-        file_path = stream_info.url or stream_info.local_path or stream_info.filename
+        file_path = (
+            stream_info.url
+            or stream_info.local_path
+            or stream_info.filename
+            or "(unknown)"
+        )
         md_content = f"Content from the zip file `{file_path}`:\n\n"
 
         with zipfile.ZipFile(file_stream, "r") as zipObj:

packages/markitdown/tests/test_module_misc.py

@@ -5,6 +5,7 @@
 import os
 import re
 import shutil
+import zipfile
 from types import SimpleNamespace
 import pytest
 from unittest.mock import MagicMock
@@ -785,6 +786,24 @@ def test_markitdown_llm() -> None:
     validate_strings(result, PPTX_TEST_STRINGS)
 
 
+def test_zip_stream_no_filename_header() -> None:
+    """Regression test: ZipConverter must not render the literal string 'None'
+    in the output header when the stream has no associated URL, local path, or
+    filename (e.g. when called via convert_stream() without stream_info)."""
+    markitdown = MarkItDown()
+
+    buf = io.BytesIO()
+    with zipfile.ZipFile(buf, "w") as zf:
+        zf.writestr("hello.txt", "Hello world")
+    buf.seek(0)
+
+    result = markitdown.convert_stream(
+        buf, stream_info=StreamInfo(mimetype="application/zip")
+    )
+    assert result.markdown.startswith("Content from the zip file `(unknown)`:\n\n")
+    assert "Hello world" in result.markdown
+
+
 def test_ipynb_accepts_non_ascii() -> None:
     """IpynbConverter.accepts() must not raise on non-ASCII binary content."""
     from markitdown.converters._ipynb_converter import IpynbConverter