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fix(#768): stringify NaN as empty string per XForms spec #770

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fix(#768): stringify NaN as empty string per XForms spec #770

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b1d1dde
fix NaN issue in coalesce
latin-panda Apr 7, 2026
912e6ce
changeset
latin-panda Apr 7, 2026
7c2ab37
refactor
latin-panda Apr 8, 2026
6a77007
fixes tests
latin-panda Apr 8, 2026
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5 changes: 5 additions & 0 deletions .changeset/yummy-meals-care.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@getodk/xpath': patch
---

Stringify NaN as an empty string according to the XForms specs.
2 changes: 1 addition & 1 deletion packages/scenario/test/instance-input.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -812,7 +812,7 @@ describe.each<InstanceRoundTripCase>([
readonly inner3: ComparableAnswer;
}

const NAN_ANSWER = stringAnswer(String(NaN));
const NAN_ANSWER = stringAnswer('');

interface MissingRepeatInstanceInputCase {
readonly detail: string;
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6 changes: 3 additions & 3 deletions packages/xforms-engine/test/instance/instance.test.ts
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Expand Up @@ -133,7 +133,7 @@ describe('Form instance state', () => {

it.each([
{ firstValue: '2', expected: '4' },
{ firstValue: '', expected: 'NaN' },
{ firstValue: '', expected: '' },
])(
'updates the calculation to $expected when its dependency value is updated to $firstValue',
({ firstValue, expected }) => {
Expand Down Expand Up @@ -331,7 +331,7 @@ describe('Form instance state', () => {
it.each([
{ firstValue: '2', expected: '6' },
{ firstValue: '0', expected: '0' },
{ firstValue: '', expected: 'NaN' },
{ firstValue: '', expected: '' },
])(
'updates the calculated value $expected while it is relevant',
({ firstValue, expected }) => {
Expand All @@ -350,7 +350,7 @@ describe('Form instance state', () => {
it.each([
{ firstValue: '2', expected: '6' },
{ firstValue: '0', expected: '0' },
{ firstValue: '', expected: 'NaN' },
{ firstValue: '', expected: '' },
])(
'updates the calculated value $expected when it becomes relevant after the calculated dependency has been updated',
({ firstValue, expected }) => {
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2 changes: 1 addition & 1 deletion packages/xpath/src/evaluations/NumberEvaluation.ts
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Expand Up @@ -18,6 +18,6 @@ export class NumberEvaluation<T extends XPathNode> extends ValueEvaluation<T, 'N

this.booleanValue = value !== 0 && !Number.isNaN(value);
this.numberValue = value;
this.stringValue = String(value);
this.stringValue = Number.isNaN(value) ? '' : String(value);
}
}
8 changes: 8 additions & 0 deletions packages/xpath/test/xforms/coalesce.test.ts
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Expand Up @@ -40,6 +40,14 @@ describe('#coalesce()', () => {
testContext.assertStringValue('coalesce(/simple/xpath/to/node, "SECOND")', 'SECOND');
});

it('should return second value if first value is NaN', () => {
testContext.assertStringValue('coalesce(1 * /simple/xpath/to/node, "0")', '0');
testContext.assertStringValue(
'coalesce(/simple/xpath/to/node * /simple/xpath/to/node, "0")',
'0'
);
});

it('coalesce(self::*)', () => {
testContext = createXFormsTestContext(`
<div id="FunctionSelectedCase">
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4 changes: 2 additions & 2 deletions packages/xpath/test/xforms/once.test.ts
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Expand Up @@ -27,8 +27,8 @@ describe('once()', () => {
});
});

it('should set value to NaN', () => {
testContext.assertStringValue('once(. * 10)', 'NaN', {
it('should set value to empty string when arithmetic on empty node produces NaN', () => {
testContext.assertStringValue('once(. * 10)', '', {
contextNode,
});
});
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2 changes: 1 addition & 1 deletion packages/xpath/test/xforms/randomize.test.ts
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Expand Up @@ -80,7 +80,7 @@ describe('randomize()', () => {
{ seed: 0, expected: 'CBEAFD' },
{ seed: NaN, expected: 'CBEAFD' },
{ seed: Infinity, expected: 'CBEAFD' },
{ seed: -Infinity, expected: 'CFBEAD' },
{ seed: -Infinity, expected: 'CBEAFD' },
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@latin-panda latin-panda Apr 8, 2026

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The old test expected 'CFBEAD' because we were incorrectly stringifying NaN as "NaN" and hashing it. The fix correctly stringifies NaN as "", which maps to seed 0 → 'CBEAFD'.

{ seed: 'floor(1.1)', expected: 'BFEACD' },
{ seed: '//xhtml:div[@id="testFunctionNodeset2"]/xhtml:p', expected: 'BFEACD' },
{ seed: MIRROR_HASH_VALUE, expected: MIRROR_HASH_SORT_ORDER },
Expand Down