Fix CSE array formula evaluation: count booleans in arithmetic operators

[ken-swyfft]

Problem

CSE (Ctrl+Shift+Enter) array formulas that use the common pattern of boolean array multiplication fail with #VALUE! errors:

{INDEX(..., MATCH(1, ($A$1:$A$10=val1)*($B$1:$B$10=val2), 0), col)}

The = comparison operators correctly produce CacheAreaEval arrays of BoolEval values (TRUE/FALSE) when in array mode. However, when the * operator then tries to multiply these arrays element-wise, all the boolean values are silently dropped, producing empty/wrong-sized arrays that cascade to #VALUE! errors.

Root Cause

In TwoOperandNumericOperation.ArrayEval, the MutableValueCollector is constructed with isReferenceBoolCounted=false:

private readonly MatrixFunction.MutableValueCollector instance = 
    new MatrixFunction.MutableValueCollector(false, true);

When CollectValues iterates over a CacheAreaEval (which is a TwoDEval), it calls CollectValue(ve, isViaReference: true, temp). With isReferenceBoolCounted=false, all BoolEval values are silently skipped in MultiOperandNumericFunction.CollectValue():

if (ve is BoolEval boolEval)
{
    if (!isViaReference || _isReferenceBoolCounted)
    {
        temp.Add(boolEval.NumberValue);
    }
    return;  // ← silently skips when isViaReference=true and _isReferenceBoolCounted=false
}

This is correct behavior for SUM-like functions (where booleans in ranges are ignored per Excel spec), but wrong for arithmetic operators in array mode, where booleans must be coerced to 0/1.

Fix

Change isReferenceBoolCounted from false to true in TwoOperandNumericOperation.ArrayEval:

private readonly MatrixFunction.MutableValueCollector instance = 
    new MatrixFunction.MutableValueCollector(true, true);

Also added ErrorEval handling in Match.EvaluateLookupRange() so that upstream errors propagate as EvaluationException rather than throwing a raw Exception.

Testing

New unit tests (TestCseArrayBooleanArithmetic.cs — 5 tests):

1. TestIndexMatchWithBooleanArrayMultiplication — End-to-end test of the {INDEX(range, MATCH(1, (col1=val1)*(col2=val2), 0))} pattern, the exact CSE formula used in real-world workbooks
2. TestBooleanArrayMultiplicationDifferentMatches — Verifies correct results across multiple lookup value combinations
3. TestBooleanArrayMultiplicationNoMatch — Confirms #N/A (not #VALUE!) when no match exists
4. TestMatchWithErrorEvalInLookupRange — Validates that Match.EvaluateLookupRange handles ErrorEval gracefully instead of throwing a raw Exception
5. TestSimpleBooleanArrayMultiplication — Direct test of element-wise multiplication of two boolean arrays

All existing NPOI tests pass (4,572 passed across net8.0 and net472, 0 failed).

Real-world validation against 56 Excel rater workbooks containing 460,000+ formula cells and 1,228 CSE array formula cells:

• Before fix: 158+ CSE array formula failures, cascading #VALUE! exceptions
• After fix: 0 CSE array formula failures, 98.4%–100% formula evaluation success across all workbooks

[tonyqus]

Thank you for the detailed description.

[tonyqus]

LGTM

[tonyqus]

I glance at your Github profile and found that we have something in common.

My last company is VRSK (insurance industry company) and the HQ of VRSK is also in NJ. What a coincidence 👯‍♂️

[ken-swyfft]

I glance at your Github profile and found that we have something in common.

My last company is VRSK (insurance industry company) and the HQ of VRSK is also in NJ. What a coincidence 👯‍♂️

Oh, interesting. Yeah, probably like most insurance companies, we use Verisk for a whole bunch of things. Swyfft is almost entirely remote (I'm in the Seattle area), but our headquarters are in New Jersey.