Fix localized VSTACK and HSTACK names

[Tobiadefami]

Context

HyperFormula 3.4.0 shipped VSTACK and HSTACK with English placeholder names in language packs where Microsoft Excel uses localized names. This PR moves the previously reviewed localization fix out of the unrelated TAKE PR and into a dedicated change.

This extracts the VSTACK/HSTACK portion of commit b902d53bc, originally authored by Kuba Sekowski.

Changes

Language	VSTACK	HSTACK
Czech	SROVNAT.SVISLE	SROVNAT.VODOROVNĚ
Danish	VSTAK	HSTAK
German	VSTAPELN	HSTAPELN
Spanish	APILARV	APILARH
Finnish	VPINO	HPINO
French	ASSEMB.V	ASSEMB.H
Hungarian	FÜGG.HALMOZÁS	VÍZSZ.HALMOZÁS
Italian	STACK.VERT	STACK.ORIZ
Norwegian	VSTAKK	HSTAKK
Dutch	VERT.STAPELEN	HOR.STAPELEN
Polish	STOS.PION	STOS.POZ
Portuguese	JUNTARV	JUNTARH
Russian	ВСТОЛБИК	ГСТОЛБИК
Turkish	DÜŞEYYIĞ	YATAYYIĞ

Indonesian and Swedish remain in English, matching Excel. The PR also adds source-verification guidance to DEV_DOCS.md and an Unreleased changelog entry.

Source verification

All 14 localized pairs and the unchanged Indonesian and Swedish pairs were checked on 2026-08-25 against Microsoft Support's current individual VSTACK/HSTACK pages, using each page title and displayed formula syntax. This caught one mismatch in the original table: Danish is VSTAK / HSTAK.

Microsoft's Danish alphabetical function index currently conflicts with those individual pages, so DEV_DOCS.md now requires checking the linked individual page rather than copying a name from the index alone.

Migration note

This is a breaking change for formulas created with HyperFormula 3.4.0 that use English VSTACK or HSTACK while one of the affected language packs is active. Those formulas must switch to the names listed above.

Validation

Companion tests: handsontable/hyperformula-tests#44

• 34/34 focused i18n tests passed.
• Full browser suite passed: 12,388 assertions in Chrome and Firefox.
• TypeScript compilation passed.
• Targeted lint completed with zero errors.
• git diff --check passed.

Types of changes

• Breaking change
• New feature or improvement
• Bug fix
• Additional language file or translation change
• Documentation change

---

Note

Medium Risk
Breaking change for stored formulas that use English VSTACK/HSTACK under affected locales; runtime behavior is unchanged once formulas use the correct localized names.

Overview
Replaces English placeholder names for VSTACK and HSTACK with Microsoft Excel’s localized identifiers in 14 built-in language packs (Czech, Danish, German, Spanish, Finnish, French, Hungarian, Italian, Norwegian, Dutch, Polish, Portuguese, Russian, Turkish). Indonesian and Swedish stay in English, consistent with Excel.

DEV_DOCS.md now requires confirming localized names against Excel (including per-locale checks on Microsoft’s individual function pages when the alphabetical index disagrees) and keeping English when Excel does not ship a translation. An Unreleased changelog entry documents the fix.

Breaking change: With one of the updated locales active, formulas that still call VSTACK or HSTACK in English (as in HyperFormula 3.4.0) must use the new localized names or they will not parse.

^{Reviewed by Cursor Bugbot for commit a6e8b1c. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cla-external-contractor-signup]

@Tobiadefami thanks for the pull request. No CLA step needed here — our records show you signed the Contributor License Agreement on 2026-07-31. That signature came from our previous signing form and has been carried over, so there is nothing for you to re-sign.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.31%. Comparing base (61ead73) to head (6719cb9).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1748   +/-   ##
========================================
  Coverage    97.31%   97.31%           
========================================
  Files          195      195           
  Lines        15719    15719           
  Branches      3455     3384   -71     
========================================
  Hits         15297    15297           
- Misses         414      422    +8     
+ Partials         8        0    -8     

Files with missing lines	Coverage Δ
src/i18n/languages/csCZ.ts	100.00% <ø> (ø)
src/i18n/languages/daDK.ts	100.00% <ø> (ø)
src/i18n/languages/deDE.ts	100.00% <ø> (ø)
src/i18n/languages/esES.ts	100.00% <ø> (ø)
src/i18n/languages/fiFI.ts	100.00% <ø> (ø)
src/i18n/languages/frFR.ts	100.00% <ø> (ø)
src/i18n/languages/huHU.ts	100.00% <ø> (ø)
src/i18n/languages/itIT.ts	100.00% <ø> (ø)
src/i18n/languages/nbNO.ts	100.00% <ø> (ø)
src/i18n/languages/nlNL.ts	100.00% <ø> (ø)
... and 4 more

... and 5 files with indirect coverage changes

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[github-actions]

Performance comparison of head (a6e8b1c) vs base (286a731)

                                     testName |    base |   head | change
-------------------------------------------------------------------------
                                      Sheet A |   502.3 | 509.31 | +1.40%
                                      Sheet B |  165.56 | 164.16 | -0.85%
                                      Sheet T |  145.95 | 145.23 | -0.49%
                                Column ranges |   478.6 | 485.88 | +1.52%
                                Sorted lookup | 14490.9 |  14609 | +0.81%
Sheet A:  change value, add/remove row/column |   16.46 |   16.6 | +0.85%
 Sheet B: change value, add/remove row/column |  147.96 |  142.9 | -3.42%
                   Column ranges - add column |  155.46 | 155.33 | -0.08%
                Column ranges - without batch |  471.32 | 488.31 | +3.60%
                        Column ranges - batch |  119.34 | 121.44 | +1.76%

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	hyperformula-docs	a6e8b1c	Commit Preview URL Branch Preview URL	Sep 02 2026, 10:06 AM

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