HF-270: Exporter honours evaluateNullToZero for bare empty cells

[marcin-kordas-hoc]

Fixes HF-270: the evaluateNullToZero config option is honoured by the interpreter (a formula reading an empty cell already coerces empty → 0) but was ignored by the Exporter, which always returned null for a bare empty cell read directly — so with the flag on, getSheetValues over [[null, '=A1']] gave [[null, 0]].

What changed

The Exporter's EmptyValue branch returns 0 when config.evaluateNullToZero is true, null otherwise. Default behaviour (flag off/absent) is byte-identical. ISBLANK still reports true for the bare empty cell either way. The CHANGELOG entry names the caveat: code relying on null from getCellValue to distinguish truly-empty from computed-zero under this flag should use ISBLANK instead.

Implemented independently from the task description (not taken from the fork referenced there).

Verification

Paired tests: hyperformula-tests@spike/hf270-null-to-zero (22 assertions across getCellValue / getSheetValues / ExportedCellChange / ISBLANK / default-off). tsc --noEmit clean, eslint --quiet clean.

🤖 Generated with Claude Code

---

Note

Medium Risk
Behavior change for export APIs when evaluateNullToZero is enabled may break code that relied on null to detect empty cells; default-off path is unchanged.

Overview
Fixes HF-270: when evaluateNullToZero is enabled, the interpreter already treats empty cells as 0 inside formulas, but Exporter.exportValue always mapped EmptyValue to null, so direct reads via getCellValue, getSheetValues, getAllSheetsValues, and ExportedCellChange stayed inconsistent (e.g. [[null, '=A1']] → [[null, 0]]).

The EmptyValue branch now returns 0 when config.evaluateNullToZero is true, otherwise null. With the flag off or absent, export behaviour is unchanged. ISBLANK still treats bare empty cells as blank either way.

CHANGELOG documents the caveat: callers that used null from export APIs to distinguish truly empty cells from computed zero under this flag should use ISBLANK instead.

^{Reviewed by Cursor Bugbot for commit 10e48b2. Bugbot is set up for automated code reviews on this repo. Configure here.}

[qunabu]

Task linked: HF-270 evaluateNullToZero works inconsistently

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	hyperformula-docs	10e48b2	Commit Preview URL Branch Preview URL	Aug 14 2026, 12:36 PM

[github-actions]

Performance comparison of head (10e48b2) vs base (61ead73)

                                     testName |   base |    head | change
-------------------------------------------------------------------------
                                      Sheet A | 492.25 |  497.94 | +1.16%
                                      Sheet B | 155.65 |   159.7 | +2.60%
                                      Sheet T | 140.21 |  141.63 | +1.01%
                                Column ranges | 467.36 |  477.88 | +2.25%
                                Sorted lookup |  14129 | 14601.1 | +3.34%
Sheet A:  change value, add/remove row/column |     16 |   15.89 | -0.69%
 Sheet B: change value, add/remove row/column | 142.39 |   131.7 | -7.51%
                   Column ranges - add column | 153.98 |  145.25 | -5.67%
                Column ranges - without batch | 469.87 |  448.41 | -4.57%
                        Column ranges - batch | 120.01 |  114.45 | -4.63%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.32%. Comparing base (61ead73) to head (10e48b2).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1738      +/-   ##
===========================================
+ Coverage    97.31%   97.32%   +0.01%     
===========================================
  Files          195      195              
  Lines        15719    15719              
  Branches      3455     3385      -70     
===========================================
+ Hits         15297    15299       +2     
- Misses         414      420       +6     
+ Partials         8        0       -8     

Files with missing lines	Coverage Δ
src/Exporter.ts	89.33% <100.00%> (+2.66%)	⬆️

... and 5 files with indirect coverage changes

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[marcin-kordas-hoc]

Paired tests PR: handsontable/hyperformula-tests#39 — merge it BEFORE this one.