[marcin-kordas-hoc]

Context

The PR makes the error thrown for a formula cell read before it was computed name that cell. It is part 6 of 7 of HF-131, stacked on #1765, and fixes #444.

• Why: the engine threw a plain Error('Value of the formula cell is not computed.') or Error('Array not computed yet.'), with no way to tell which cell it was.
• What changed:
  • hyperformula/src/errors.ts: CellValueNotComputedError with a read-only address and the address in its message.
  • hyperformula/src/DependencyGraph/FormulaVertex.ts: the scalar and array formula vertices throw it.
  • hyperformula/src/index.ts: exported by name and as HyperFormula.CellValueNotComputedError.
• Result: the thrown error is instanceof CellValueNotComputedError and instanceof Error, and its message reads Value of the formula cell (sheet = 0, row = 0, col = 0) is not computed.

How did you test your changes?

• Paired tests: handsontable/hyperformula-tests#64 on fix/hf-131-issue-444-addresses, with the new unit/errors.spec.ts (4 tests, both vertex types).
• That spec passes against this head and fails against HF-131 (5/7): no error reports a cell that did not produce it #1765'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

• New exported class CellValueNotComputedError (also HyperFormula.CellValueNotComputedError).
• The message of this thrown error changes. Code that matched the old message text needs to match the class instead.

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. Fixes Add cellAddress to "Value of the formula cell is not computed." error message #444.
2. 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	a95916b	Commit Preview URL Branch Preview URL	Oct 23 2026, 07:21 AM

[github-actions]

Performance comparison of head (a95916b) vs base (ae97e21)

                                     testName |    base |    head | change
--------------------------------------------------------------------------
                                      Sheet A |  515.87 |   508.1 | -1.51%
                                      Sheet B |  168.92 |  166.35 | -1.52%
                                      Sheet T |  150.14 |  145.26 | -3.25%
                                Column ranges |  488.25 |  475.04 | -2.71%
                                Sorted lookup | 14706.8 | 13886.1 | -5.58%
Sheet A:  change value, add/remove row/column |    16.3 |   16.46 | +0.98%
 Sheet B: change value, add/remove row/column |  141.84 |  133.07 | -6.18%
                   Column ranges - add column |  160.33 |  152.32 | -5.00%
                Column ranges - without batch |  490.06 |   465.7 | -4.97%
                        Column ranges - batch |  123.45 |  115.09 | -6.77%

[Tobiadefami]

The implementation looks good.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.40%. Comparing base (ae97e21) to head (a95916b).

Additional details and impacted files

@@                      Coverage Diff                       @@
##           fix/hf-131-rootless-origin    #1766      +/-   ##
==============================================================
+ Coverage                       97.38%   97.40%   +0.01%     
==============================================================
  Files                             207      207              
  Lines                           16343    16349       +6     
  Branches                         3630     3630              
==============================================================
+ Hits                            15916    15925       +9     
+ Misses                            419      416       -3     
  Partials                            8        8              

Files with missing lines	Coverage Δ
hyperformula/src/DependencyGraph/FormulaVertex.ts	86.71% <100.00%> (+2.46%)	⬆️
hyperformula/src/errors.ts	100.00% <100.00%> (ø)
hyperformula/src/index.ts	100.00% <100.00%> (ø)

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