Makes timezone formatting as duration more robust

Fixes support of cases like "+00:00"

lib/functions/XPathFunctions.ts

@@ -74,24 +74,26 @@ export function formatDayTimeDuration(timezone: string): string | undefined {
   if (!timezone) {
     return;
   }
-  if (timezone.startsWith('Z')) {
-    return 'PT0S';
-  }
-  // Split string
-  const [ sign, h1Raw, h2Raw, _, m1Raw, m2Raw ] = timezone;
 
-  // Cut of leading zero, set to empty string if 0, and append H;
-  const h1 = h1Raw !== '0' ? h1Raw : '';
-  const h2 = h1 || h2Raw !== '0' ? h2Raw : '';
-  const hours = h1 + h2 ? `${h1 + h2}H` : '';
+  let sign = '';
+  let hours = 0;
+  let minutes = 0;
+  if (timezone !== 'Z') {
+    sign = timezone.startsWith('-') ? '-' : '';
+    hours = Number.parseInt(timezone.slice(1, 3), 10);
+    minutes = Number.parseInt(timezone.slice(4, 6), 10);
+  }
 
-  // Same as in hours
-  const m1 = m1Raw !== '0' ? m1Raw : '';
-  const m2 = m1 || m2Raw !== '0' ? m2Raw : '';
-  const minutes = m1 + m2 ? `${m1 + m2}M` : '';
+  if (hours === 0 && minutes === 0) {
+    return 'PT0S';
+  }
 
-  // Concat sign and time and mandatory separators
-  const time = `${hours}${minutes}`;
-  const signNoPlus = sign === '-' ? '-' : '';
-  return `${signNoPlus}PT${time}`;
+  let time = `${sign}PT`;
+  if (hours > 0) {
+    time += `${hours}H`;
+  }
+  if (minutes > 0) {
+    time += `${minutes}M`;
+  }
+  return time;
 }

test/integration/functions/XPathConstructors.test.ts

@@ -232,6 +232,9 @@ describe('evaluation of XPath constructors', () => {
       testTable: `
         "1999-03-17T06:00:00Z"^^xsd:dateTime = "1999-03-17T06:00:00Z"^^xsd:dateTime
         "1999-03-17T06:00:00Z" = "1999-03-17T06:00:00Z"^^xsd:dateTime
+        "1999-03-17T06:00:00+02:30" = "1999-03-17T06:00:00+02:30"^^xsd:dateTime
+        "1999-03-17T06:00:00" = "1999-03-17T06:00:00"^^xsd:dateTime
+        "1999-03-17" = "1999-03-17"^^xsd:dateTime
       `,
       errorTable: `
         "foo" = ''

test/integration/functions/op.timezone.test.ts

@@ -0,0 +1,19 @@
+import { Notation } from '../../util/TestTable';
+import { runTestTable } from '../../util/utils';
+
+describe('evaluation of \'timezone\'', () => {
+  runTestTable({
+    operation: 'timezone',
+    arity: 1,
+    notation: Notation.Function,
+    testTable: `
+      "2000-01-01T00:00:00Z"^^xsd:dateTime = "PT0S"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00+00:00"^^xsd:dateTime = "PT0S"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00-00:00"^^xsd:dateTime = "PT0S"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00+00:30"^^xsd:dateTime = "PT30M"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00+01:00"^^xsd:dateTime = "PT1H"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00+01:30"^^xsd:dateTime = "PT1H30M"^^xsd:dayTimeDuration
+      "2000-01-01T00:00:00-01:30"^^xsd:dateTime = "-PT1H30M"^^xsd:dayTimeDuration
+      `,
+  });
+});