HF-24: add stringifyCurrency config callback for TEXT

[marcin-kordas-hoc]

Summary

Adds a stringifyCurrency config option mirroring the existing stringifyDateTime / stringifyDuration callbacks. When set, the TEXT function consults the callback before falling through to the built-in number formatter, so users can plug in locale-aware currency formatting (for example via Intl.NumberFormat or a third-party library) without bringing currency data into the HyperFormula core.

The default implementation returns undefined so existing TEXT behavior is preserved bit-for-bit.

Linked

• Spec: agents/hyperformula/docs/specs/2026-04-21-hf-24-currency-in-text.md
• Tech rationale: agents/hyperformula/docs/specs/2026-04-24-hf-24-tech-rationale.md
• Implementation plan: agents/hyperformula/docs/specs/2026-04-27-hf-24-stringify-currency-plan.md

Tests

Tests added in the matching feature/hf-24-stringify-currency branch of handsontable/hyperformula-tests. Coverage:

• default callback returns undefined
• custom callback intercepts currency formats
• callback opts out (returns undefined) → fall-through to numberFormat
• date / duration formats are not intercepted by stringifyCurrency
• six representative Excel format strings handled by the docs Intl.NumberFormat adapter (USD, EUR via LCID, JPY via LCID, PLN via LCID, accounting two-section, fall-through)

Notes

• PLN format string change: the spec example originally used #,##0.00 "zł" (trailing quoted symbol). HF's formula parser does not accept embedded quotes inside TEXT format strings, so the docs example and the corresponding test were swapped to use [$zł-415] #,##0.00 (LCID-tagged symbol). The adapter still recognizes the trailing-quote pattern for users invoking the callback outside HyperFormula.
• Pre-existing lint errors (9, all in test/hyperformula-tests/unit/memory-management.spec.ts) are unrelated to this PR — they originate from PR NUMBER type precision is not precise enough #4 of the private repo and should be fixed in a separate ticket.

Test plan

• CI green on handsontable/hyperformula PR
• CI green on handsontable/hyperformula-tests PR (matching branch)
• Manual: build docs locally, render the new "Currency integration" section under Date and time handling, copy-paste the adapter into a fresh sandbox to confirm it runs against Intl.NumberFormat on Node 14+

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Note

Medium Risk
Touches the TEXT formatting pipeline by inserting a new callback hook; default behavior is preserved, but a misbehaving callback could change output for any TEXT formatting call.

Overview
Adds a new stringifyCurrency configuration callback (mirroring stringifyDateTime/stringifyDuration) that lets callers intercept TEXT(value, format) and return a currency-formatted string.

format() now consults config.stringifyCurrency(value, formatArg) after date/duration formatting and before the built-in numberFormat fallback; the shipped defaultStringifyCurrency returns undefined to keep existing output unchanged.

Documentation and changelog are updated with a new Currency integration guide section and examples (including an Intl.NumberFormat adapter).

^{Reviewed by Cursor Bugbot for commit 0246ce0. Bugbot is set up for automated code reviews on this repo. Configure here.}

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Private tests PR: handsontable/hyperformula-tests#10

[qunabu]

Task linked: HF-24 Support popular currency formats in TEXT function

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[marcin-kordas-hoc]

Superseded by #1665.

Same content (same HEAD SHA), but routed from the upstream branch instead of fork. The fork-side PR was hitting a structural CI failure: 3 matrix checks (Test performance, unit-tests, browser-tests) require the DEPLOY_TOKEN secret to clone the private hyperformula-tests repo, and GitHub does not expose org secrets to fork-originated workflow runs. Re-routing to the upstream branch resolves that.

Worktree push routing for future PRs is being fixed locally so this won't repeat.