[marcin-kordas-hoc]

Context

The PR adds DetailedCellError.hasMessage, so a consumer can tell an error with no message from one with an empty message. It is part 3 of 7 of HF-131, stacked on #1762.

• Why: DetailedCellError.message is '' both when the error had no message and when the message was deliberately empty. A custom function may omit the message, because the CellError constructor keeps it optional.
• What changed:
  • hyperformula/src/CellValue.ts: hasMessage is true when the underlying CellError has a message, even an empty one.
  • docs/guide/custom-functions.md: one paragraph on message and hasMessage.
  • hyperformula/test/_setupFiles/matchers/cellErrorComparison.ts: toEqualError ignores the new field.
• Result: =1/0 reports hasMessage: true; an error value typed into a cell reports hasMessage: false and message: ''.

How did you test your changes?

• Paired tests: handsontable/hyperformula-tests#61 on feat/hf-131-has-message, with 4 new tests in unit/CellValueExporter.spec.ts.
• That spec passes against this head (9 tests) and fails against HF-131 (2/7): the origin/propagation mechanism, plus the same guarantee outside the interpreter #1762's head.
• CI is green on this head, except the repository-wide FOSSA license check.

Compatibility with Excel and Google Sheets

Not applicable: no formula result changes.

Public API changes

• DetailedCellError.hasMessage: boolean (new, read-only). toString() and valueOf() are unchanged.

Out of scope and follow-ups

None.

Types of changes

• Breaking change (existing functionality no longer works as before) – agreed with the maintainers
• New feature or improvement (a non-breaking change that adds functionality)
• Bug fix (a non-breaking change that fixes an issue)
• Additional language file, or a change to an existing language file (translations)
• Change to the documentation

Related issues

1. Part of Improve the formula error messages #1547 (HF-131).

Checklist

• My pull request meets the Definition of Done. External contributors: see also Contributing to HyperFormula.
• I have signed the Contributor License Agreement.
• I read my own diff end to end before requesting a review.
• I added a CHANGELOG.md entry, written by the changelog rules – or none is needed (docs, tests or tooling only).
• I updated the documentation and JSDoc to match the change.
• Breaking change only: I added a section to the migration guide.
• I updated the dev-docs/ pages this change affects – or none needed it.

[qunabu]

Task linked: HF-131 Verbose and actionable formula error messages

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	hyperformula-docs	9d436c4	Commit Preview URL Branch Preview URL	Oct 23 2026, 07:17 AM

[github-actions]

Performance comparison of head (9d436c4) vs base (c5feea6)

                                     testName |   base |    head | change
-------------------------------------------------------------------------
                                      Sheet A | 503.52 |  500.85 | -0.53%
                                      Sheet B | 166.25 |  161.39 | -2.92%
                                      Sheet T |  143.9 |  141.35 | -1.77%
                                Column ranges |  535.1 |  530.38 | -0.88%
                                Sorted lookup |  15218 | 15134.7 | -0.55%
Sheet A:  change value, add/remove row/column |  19.75 |   18.72 | -5.22%
 Sheet B: change value, add/remove row/column | 145.69 |  152.53 | +4.69%
                   Column ranges - add column | 168.37 |  168.56 | +0.11%
                Column ranges - without batch | 530.13 |  509.74 | -3.85%
                        Column ranges - batch | 129.87 |  128.64 | -0.95%

[Tobiadefami]

Looks good. Verified that hasMessage distinguishes an omitted message from an explicitly empty string, including through cell references.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.34%. Comparing base (c5feea6) to head (9d436c4).

Additional details and impacted files

@@                               Coverage Diff                               @@
##           feat/hf-131-error-messages-outside-interpreter    #1763   +/-   ##
===============================================================================
  Coverage                                           97.34%   97.34%           
===============================================================================
  Files                                                 207      207           
  Lines                                               16322    16323    +1     
  Branches                                             3621     3621           
===============================================================================
+ Hits                                                15889    15890    +1     
  Misses                                                425      425           
  Partials                                                8        8           

Files with missing lines	Coverage Δ
hyperformula/src/CellValue.ts	80.00% <100.00%> (+2.22%)	⬆️

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