Distance function: multiple arguments

.changeset/funny-items-know.md

@@ -0,0 +1,8 @@
+---
+"@getodk/xpath": patch
+---
+
+Distance function can now accepts multiple arguments.
+This makes it easier to compute the distance between multiple points within a form's primary instance.
+Previously, to achieve this, you'd have to introduce a calculate which concatenates those points together,
+and then call the distance function with a reference to that calculate as the argument.

packages/xpath/src/functions/xforms/geo.ts

@@ -86,13 +86,12 @@
 	context: EvaluationContext<T>,
 	expression: EvaluableArgument
 ): Line[] => {
-	const points = evaluatePoints(context, expression);
-
+	const points = expression.flatMap((el) => evaluatePoints(context, el));
 	if (points.length < 2) {
 		return [INVALID_LINE];
 	}
 
 	return Array.from(pairwise(points)).map((line) => {
 		const [start, end] = line;
 
 		if (start === INVALID_POINT || end === INVALID_POINT) {
@@ -172,7 +171,7 @@
 	'area',
 	[{ arityType: 'required' }],
 	(context, [expression]) => {
-		const lines = evaluateLines(context, expression!);
+		const lines = evaluateLines(context, [expression!]);
 
 		if (lines.some(isInvalidLine)) {
 			return NaN;
@@ -209,9 +208,9 @@
 
 export const distance = new NumberFunction(
 	'distance',
-	[{ arityType: 'required' }],
-	(context, [expression]) => {
-		const lines = evaluateLines(context, expression!);
+	[{ arityType: 'required' }, { arityType: 'variadic' }],
+	(context, args) => {
+		const lines = evaluateLines(context, args);
 
 		if (lines.some(isInvalidLine)) {
 			return NaN;

packages/xpath/test/xforms/area.test.ts → packages/xpath/test/xforms/geo.test.ts

@@ -43,7 +43,7 @@ describe('distance() and area() functions', () => {
 		});
 	});
 
-	describe('area with nodes', () => {
+	describe('area and distance with nodes', () => {
 		beforeEach(() => {
 			testContext = createXFormsTestContext(`
         <root>