Fixes

Author: dkhalanskyjb

core/common/test/InstantTest.kt

@@ -94,8 +94,7 @@ class InstantTest {
             Pair("2020-01-01T00:01:01.010203040+17:59", "2019-12-31T06:02:01.010203040Z"),
             Pair("2020-01-01T00:01:01+00", "2020-01-01T00:01:01Z"),
         )
-        strings.forEach {
-            val (str, strInZ) = it
+        strings.forEach { (str, strInZ) ->
             val instant = Instant.parse(str)
             assertEquals(Instant.parse(strInZ), instant, str)
             assertEquals(strInZ, instant.toString(), str)
@@ -124,7 +123,7 @@ class InstantTest {
 
         for (instant in instants) {
             for (offset in offsets) {
-                val str = instant.toStringWithOffset(TimeZone.of("+03:12:14") as ZoneOffset)
+                val str = instant.toStringWithOffset(offset)
                 assertEquals(instant, Instant.parse(str))
             }
         }

core/js/src/Instant.kt

@@ -83,13 +83,16 @@ public actual class Instant internal constructor(internal val value: jtInstant)
             throw e
         }
 
-        /** A workaround for a bug where the string representations of Instant that have an offset of the form
-         * "+XX" are not recognized by [jtOffsetDateTime.parse], while "+XX:XX" work fine.
+        /** A workaround for the string representations of Instant that have an offset of the form
+         * "+XX" not being recognized by [jtOffsetDateTime.parse], while "+XX:XX" work fine.
          * See [the Github issue](https://github.com/js-joda/js-joda/issues/492). */
         private fun fixOffsetRepresentation(isoString: String): String {
-            val time = isoString.split("T").elementAtOrNull(1) ?: return isoString
-            val offset = time.split("+", "-").elementAtOrNull(1) ?: return isoString
-            return if (offset.contains(":")) isoString else "$isoString:00"
+            val time = isoString.indexOf('T', ignoreCase = true)
+            if (time == -1) return isoString // the string is malformed
+            val offset = isoString.indexOfLast { c -> c == '+' || c == '-' }
+            if (offset < time) return isoString // the offset is 'Z' and not +/- something else
+            val separator = isoString.indexOf(':', offset) // if there is a ':' in the offset, no changes needed
+            return if (separator != -1) isoString else "$isoString:00"
         }
 
         public actual fun fromEpochSeconds(epochSeconds: Long, nanosecondAdjustment: Long): Instant = try {

core/jvm/src/Instant.kt

@@ -72,9 +72,12 @@ public actual class Instant internal constructor(internal val value: jtInstant)
         /** A workaround for a quirk of the JDKs older than 11 where the string representations of Instant that have an
          * offset of the form "+XX" are not recognized by [jtOffsetDateTime.parse], while "+XX:XX" work fine. */
         private fun fixOffsetRepresentation(isoString: String): String {
-            val time = isoString.split("T").elementAtOrNull(1) ?: return isoString
-            val offset = time.split("+", "-").elementAtOrNull(1) ?: return isoString
-            return if (offset.contains(":")) isoString else "$isoString:00"
+            val time = isoString.indexOf('T', ignoreCase = true)
+            if (time == -1) return isoString // the string is malformed
+            val offset = isoString.indexOfLast { c -> c == '+' || c == '-' }
+            if (offset < time) return isoString // the offset is 'Z' and not +/- something else
+            val separator = isoString.indexOf(':', offset) // if there is a ':' in the offset, no changes needed
+            return if (separator != -1) isoString else "$isoString:00"
         }
 
         public actual fun fromEpochSeconds(epochSeconds: Long, nanosecondAdjustment: Long): Instant = try {