Every ECMA-376 built-in numFmtId (id < 164) used on a cell produces a <cellXfs>/<xf> that references that id, with no explicit <numFmt> entry emitted in <numFmts>.
Library verdicts: python-xlsx: — xlsxjs: pass
| Feature id | xlsx/number-format-builtin--id5 |
|---|---|
| Format | xlsx |
| Category | cell-formatting |
| Family | xlsx/number-format-builtin |
| Axis values | numfmt=id5 |
| Spec | ecma-376-5-part-1 § 18.8.30 numFmt |
| ID / part | Predicate | XPath | python-xlsx | xlsxjs |
|---|---|---|---|---|
numfmt-id5-referencedxl/styles.xml | existA <xf> in <cellXfs> must reference the expected built-in numFmtId. Built-in ids (< 164) are implicit: no <numFmt> entry is required or expected. | //x:cellXfs/x:xf[@numFmtId='5'] | — | — |
| ID | Predicate | Selector | python-xlsx | xlsxjs |
|---|---|---|---|---|
numfmt-id5-cell-present | css_selector/ existThe rendered sheet must contain at least one cell; renderer-specific numFmt application is out of scope for this family. | section.xlsx td | — | pass |
sheet-count-id5 | css_selector/ equal-countExactly one rendered sheet section per case. Catches renderers that emit zero sheets (hard failure). | section.xlsx | — | — |
scripts/gen_number_format_builtin.py
#!/usr/bin/env python3
"""Generate a ``fixtures/xlsx/number-format-builtin--id<N>.xlsx`` fixture.
Parameterised generator for the ``xlsx/number-format-builtin`` manifest.
Writes a minimal one-sheet workbook with cell A1 set to a numeric value
and its ``number_format`` drawn from ``BUILTIN_FORMATS[num_fmt_id]``.
Excel treats these codes as built-in: the resulting workbook references
the numFmtId from ``<cellXfs>/<xf>`` without emitting an explicit
``<numFmt>`` entry in ``<numFmts>``.
"""
from __future__ import annotations
import argparse
import datetime as _dt
from pathlib import Path
from xlsx import Workbook
from xlsx.styles.numbers import BUILTIN_FORMATS
_REPO_ROOT = Path(__file__).resolve().parent.parent
_REPRODUCIBLE_DT = _dt.datetime(2000, 1, 1, 0, 0, 0)
def _write(num_fmt_id: int, out: Path) -> None:
if num_fmt_id not in BUILTIN_FORMATS:
raise ValueError(
f"num_fmt_id {num_fmt_id} is not a built-in format; "
f"valid ids: {sorted(BUILTIN_FORMATS)}"
)
wb = Workbook()
ws = wb.active
ws["A1"] = 42.5
ws["A1"].number_format = BUILTIN_FORMATS[num_fmt_id]
out.parent.mkdir(parents=True, exist_ok=True)
wb.save(out, zip_date_time=_REPRODUCIBLE_DT)
def main() -> int:
parser = argparse.ArgumentParser()
parser.add_argument(
"--num-fmt-id",
type=int,
required=True,
help="Built-in numFmtId (key in xlsx.styles.numbers.BUILTIN_FORMATS)",
)
parser.add_argument(
"--out",
required=True,
help="Output fixture path (relative to repo root or absolute)",
)
args = parser.parse_args()
out_path = Path(args.out)
if not out_path.is_absolute():
out_path = _REPO_ROOT / out_path
_write(args.num_fmt_id, out_path)
print(out_path)
return 0
if __name__ == "__main__":
raise SystemExit(main())
{
"$schema": "../manifest.schema.json",
"id": "xlsx/number-format-builtin--id5",
"kind": "literal",
"title": "Built-in number-format IDs",
"format": "xlsx",
"category": "cell-formatting",
"summary": "Every ECMA-376 built-in numFmtId (id < 164) used on a cell produces a <cellXfs>/<xf> that references that id, with no explicit <numFmt> entry emitted in <numFmts>.",
"spec": {
"source": "ecma-376-5-part-1",
"clause": "18.8.30",
"element": "numFmt",
"rnc_reference": "spec/ecma-376-5/part-1/rnc/SpreadsheetML.rnc",
"xsd_reference": "spec/ecma-376-5/part-1/xsd/sml.xsd",
"notes": "ECMA-376 Part 1 clause 18.8.30 enumerates a fixed table of built-in numFmtIds (0='General', 1='0', 2='0.00', 9='0%', 10='0.00%', 14='mm-dd-yy', 37='#,##0_);(#,##0)', ...). The built-in ids reserved by the spec do NOT appear as explicit <numFmt formatCode=.../> entries in xl/styles.xml's <numFmts> — compliant writers omit them and just reference the id from <cellXfs>/<xf>. Only CUSTOM formats (id >= 164) produce a <numFmt> entry. This family parameterises over every id in python-xlsx's xlsx.styles.numbers.BUILTIN_FORMATS (45 entries spanning 0-22, 37-49, and the ja-JP locale block 50-58). Each expanded case targets a distinct fixture xlsx/number-format-builtin--id<N>.xlsx generated with ws['A1'].number_format = BUILTIN_FORMATS[id]. The sole assertion checks that a <xf> in <cellXfs> references the expected numFmtId. SpreadsheetML parts use a default namespace with no prefix; XPath needs an explicit binding (here 'x'). Note: the ja-JP locale block 50-58 contains duplicate format codes per spec. Four groups: (50, 57), (51, 54, 58), (52, 55), (53, 56). Since python-xlsx 2026.05.x (commit bc27371) BUILTIN_FORMATS_REVERSE picks the FIRST id for each duplicate code, so ids 50, 51, 52, 53 round-trip to themselves while the higher-numbered duplicates (54-58) are unreachable via round-trip. This family deliberately includes only the canonical (lowest-id) members of each duplicate group. Higher-id duplicates are inherently un-round-trippable given first-wins semantics and are excluded rather than authored as known-failures."
},
"fixtures": {
"machine": "xlsx/number-format-builtin--id5"
},
"generator": {
"python": "scripts/gen_number_format_builtin.py",
"arg_template": "--num-fmt-id {numfmt.num_fmt_id} --out fixtures/xlsx/number-format-builtin--{numfmt.id}.xlsx"
},
"_expansion": {
"parent_id": "xlsx/number-format-builtin",
"bindings": {
"numfmt": "id5"
}
},
"assertions": [
{
"id": "numfmt-id5-referenced",
"part": "xl/styles.xml",
"namespaces": {
"x": "http://schemas.openxmlformats.org/spreadsheetml/2006/main"
},
"xpath": "//x:cellXfs/x:xf[@numFmtId='5']",
"must": "exist",
"description": "A <xf> in <cellXfs> must reference the expected built-in numFmtId. Built-in ids (< 164) are implicit: no <numFmt> entry is required or expected."
}
],
"render_assertions": [
{
"id": "numfmt-id5-cell-present",
"kind": "css_selector",
"selector": "section.xlsx td",
"must": "exist",
"description": "The rendered sheet must contain at least one cell; renderer-specific numFmt application is out of scope for this family."
},
{
"id": "sheet-count-id5",
"kind": "css_selector",
"selector": "section.xlsx",
"must": "equal-count",
"count": 1,
"description": "Exactly one rendered sheet section per case. Catches renderers that emit zero sheets (hard failure)."
}
]
}
