Bug: _element_size fails for tables without API indices — blocks table insertion in new tabs/headers/footers/footnotes

[sripathikrishnan]

Parent Epic

#44

Bug

_element_size() in lower.py:2492 requires startIndex/endIndex to compute a table's character size. Synthetic content (new tab, new header, new footer, new footnote) has no API indices, so any path through _lower_content_insert with a table element raises NotImplementedError.

Root Cause

# lower.py:2492
def _element_size(el: StructuralElement) -> int:
    if el.paragraph is not None:
        return utf16_len(_para_text(el.paragraph))  # works
    if el.section_break is not None:
        return 1  # works
    start, end = _element_range(el)
    if start is not None and end is not None:
        return end - start
    raise NotImplementedError(...)  # tables hit this

For paragraphs, size is computed from text. For tables, it falls through to startIndex/endIndex which don't exist on synthetic content.

Affected Paths

All 5 content containers when creating a new segment:

• addDocumentTab → body with table
• createHeader → header with table
• createFooter → footer with table
• createFootnote → footnote with table
• Any combination: paragraph → table → paragraph (running index breaks at table)

Suggested Fix

Compute table size from cell contents:

table_size = 1 (table opener) + sum_per_row(1 (row opener) + sum_per_cell(1 (cell opener) + cell_content_size))

Where cell_content_size recursively uses _element_size on cell content elements.

xfail Tests (7)

• TestNewTabWithTable::test_new_tab_with_table
• TestNewTabWithTable::test_new_tab_with_table_only
• TestNewTabWithTable::test_new_tab_with_multi_paragraph_table_cell
• TestElementSizeCascade::test_new_header_with_table_content
• TestElementSizeCascade::test_new_footer_with_table_content
• TestElementSizeCascade::test_new_footnote_with_table_content
• TestElementSizeCascade::test_new_tab_para_table_para
• TestNewHeaderMixedContent::test_new_header_text_then_table