nexu-io/open-design · error · ValueError

render_for_html_comparison requires at least one report

Error message

render_for_html_comparison requires at least one report

What it means

render_for_html_comparison requires at least one (label, Report) pair because it builds comparison metadata and quality notes by reading entity_reports[0]. An empty list would IndexError at main_report access, so the function guards up front with ValueError.

Source

Thrown at design-templates/last30days/scripts/lib/render.py:218

    # the same warnings via collect_html_warnings() routed to stderr by the
    # CLI, so they can fix quality issues before sharing.
    _append_html_footer(lines, report, save_path)
    return "\n".join(lines).strip() + "\n"


def render_for_html_comparison(
    entity_reports: list[tuple[str, schema.Report]],
    synthesis_md: str | None = None,
    *,
    save_path: str | None = None,
) -> str:
    """Render comparison markdown intended for shareable HTML conversion.

    Same semantics as render_for_html(), but metadata and data quality notes
    are aggregated across the compared entities.
    """
    if not entity_reports:
        raise ValueError("render_for_html_comparison requires at least one report")

    entities = [label for label, _ in entity_reports]
    main_report = entity_reports[0][1]
    meta = (
        f"<!-- META: {main_report.range_from} to {main_report.range_to} "
        f"· comparing {len(entities)}: {', '.join(entities)} -->"
    )
    lines = [
        *_render_badge(),
        meta,
    ]
    if synthesis_md:
        lines.extend(["", synthesis_md.strip()])
    # Comparison data quality notes also go to stderr, not into the artifact.
    _append_html_footer(lines, main_report, save_path)
    return "\n".join(lines).strip() + "\n"

View on GitHub (pinned to 5be4028344)

Solutions

1. Ensure entity_reports contains at least the main topic's (label, Report) before calling.
2. If comparison yielded zero entities, fall back to the single-entity render_for_html(report) path.
3. Guard the caller: if not entity_reports, skip rendering or raise a clearer upstream error.

Example fix

# before
md = render_for_html_comparison(entity_reports)  # entity_reports == []

# after
if not entity_reports:
    md = render_for_html(main_report, save_path=save_path)
else:
    md = render_for_html_comparison(entity_reports, save_path=save_path)

def safe_render_for_html_comparison(entity_reports, synthesis_md=None, save_path=None):
    if not entity_reports:
        raise ValueError("cannot render comparison: entity_reports is empty")
    return render_for_html_comparison(entity_reports, synthesis_md, save_path=save_path)

null

null

When it happens

Trigger: Calling render_for_html_comparison([]) directly, or passing the result of a comparison step that produced zero entity reports (e.g. all competitor resolutions failed and the caller did not fall back to the single-entity renderer).

Common situations: Comparison run where every competitor lookup returned empty and the caller forwarded the empty list instead of degrading to render_for_html. Programmatic use that builds entity_reports from a filter that removed everything.

Related errors

• render_comparison_multi requires at least one report
• render_comparison_multi_context requires at least one report
• invalid JSON in ${filePath}: ${message}
• ${filePath} must contain a JSON object
• ARTIFACT_MANIFEST_INVALID

AI-assisted analysis of nexu-io/open-design@5be4028344 (2026-08-12). Data as JSON: /api/errors/db6b8262e68b47c6. Report an issue: GitHub.