From 70ba459f7077774aef32d189c63809356fc9f63b Mon Sep 17 00:00:00 2001
From: brontolosone <177225737+brontolosone@users.noreply.github.com>
Date: Fri, 25 Oct 2024 18:16:10 +0000
Subject: [PATCH] throw when calling distance() with 0 arguments

---
 .../src/evaluator/functions/FunctionImplementation.ts     | 8 +++++++-
 packages/xpath/src/functions/xforms/geo.ts                | 2 +-
 packages/xpath/test/xforms/{area.test.ts => geo.test.ts}  | 2 +-
 3 files changed, 9 insertions(+), 3 deletions(-)
 rename packages/xpath/test/xforms/{area.test.ts => geo.test.ts} (99%)

diff --git a/packages/xpath/src/evaluator/functions/FunctionImplementation.ts b/packages/xpath/src/evaluator/functions/FunctionImplementation.ts
index 8b973d665..6d164f7cd 100644
--- a/packages/xpath/src/evaluator/functions/FunctionImplementation.ts
+++ b/packages/xpath/src/evaluator/functions/FunctionImplementation.ts
@@ -39,7 +39,7 @@ export class InvalidArgumentError extends Error {
 	}
 }
 
-export type ParameterArityType = 'optional' | 'required' | 'variadic';
+export type ParameterArityType = 'optional' | 'required' | 'variadic' | 'variadic+' ;
 
 export type ParameterTypeHint =
 	// | 'lazy' // TODO: it might be good to *explicitly* mark certain parameters
@@ -127,6 +127,12 @@ export class FunctionImplementation<Length extends number> {
 							max: Infinity,
 						};
 
+					case 'variadic+':
+						return {
+							min: acc.min + 1,
+							max: Infinity,
+						};
+
 					default:
 						throw new UnreachableError(arityType);
 				}
diff --git a/packages/xpath/src/functions/xforms/geo.ts b/packages/xpath/src/functions/xforms/geo.ts
index 1414847cd..48146ea4c 100644
--- a/packages/xpath/src/functions/xforms/geo.ts
+++ b/packages/xpath/src/functions/xforms/geo.ts
@@ -202,7 +202,7 @@ const sum = (values: readonly number[]) => {
 
 export const distance = new NumberFunction(
 	'distance',
-	[{ arityType: 'variadic' }],
+	[{ arityType: 'variadic+' }],
 	(context, args) => {
 		const lines = evaluateLines(context, args);
 
diff --git a/packages/xpath/test/xforms/area.test.ts b/packages/xpath/test/xforms/geo.test.ts
similarity index 99%
rename from packages/xpath/test/xforms/area.test.ts
rename to packages/xpath/test/xforms/geo.test.ts
index 1adcf1da7..8d9f5eae8 100644
--- a/packages/xpath/test/xforms/area.test.ts
+++ b/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>