Fix issues with UUIDs with leading zeroes. Fixes #109

api/src/main/java/com/velocitypowered/api/util/UuidUtils.java

@@ -1,6 +1,7 @@
 package com.velocitypowered.api.util;
 
 import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
 import org.checkerframework.checker.nullness.qual.NonNull;
 
 import java.nio.charset.StandardCharsets;
@@ -36,7 +37,8 @@ public final class UuidUtils {
      */
     public static @NonNull String toUndashed(final @NonNull UUID uuid) {
         Preconditions.checkNotNull(uuid, "uuid");
-        return Long.toUnsignedString(uuid.getMostSignificantBits(), 16) + Long.toUnsignedString(uuid.getLeastSignificantBits(), 16);
+        return Strings.padStart(Long.toHexString(uuid.getMostSignificantBits()), 16, '0') +
+                Strings.padStart(Long.toHexString(uuid.getLeastSignificantBits()), 16, '0');
     }
 
     /**

api/src/test/java/com/velocitypowered/api/util/UuidUtilsTest.java

@@ -5,11 +5,24 @@ import org.junit.jupiter.api.Test;
 import java.util.UUID;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 class UuidUtilsTest {
     private static final UUID EXPECTED_DASHED_UUID = UUID.fromString("6b501978-d3be-4f33-bcf6-6e7808f37a0d");
     private static final String ACTUAL_UNDASHED_UUID = EXPECTED_DASHED_UUID.toString().replace("-", "");
 
+    private static final UUID ISSUE_109_ZERO_UUID = new UUID(0, 0);
+    private static final String ISSUE_109_ZERO_UUID_UNDASHED = "00000000000000000000000000000000";
+
+    private static final UUID ISSUE_109_ONE_LSB_UUID = new UUID(0, 1);
+    private static final String ISSUE_109_ONE_LSB_UUID_UNDASHED = "00000000000000000000000000000001";
+
+    private static final UUID ISSUE_109_ONE_MLSB_UUID = new UUID(1, 1);
+    private static final String ISSUE_109_ONE_MLSB_UUID_UNDASHED = "00000000000000010000000000000001";
+
+    private static final UUID ISSUE_109_LEADING_ZERO_UUID = UUID.fromString("0d470a25-0416-48a1-b7a6-2a27aa5eb251");
+    private static final String ISSUE_109_LEADING_ZERO_UNDASHED = "0d470a25041648a1b7a62a27aa5eb251";
+
     private static final UUID TEST_OFFLINE_PLAYER_UUID = UUID.fromString("708f6260-183d-3912-bbde-5e279a5e739a");
     private static final String TEST_OFFLINE_PLAYER = "tuxed";
 
@@ -27,4 +40,28 @@ class UuidUtilsTest {
     void toUndashed() {
         assertEquals(ACTUAL_UNDASHED_UUID, UuidUtils.toUndashed(EXPECTED_DASHED_UUID), "UUIDs do not match");
     }
+
+    @Test
+    void zeroUuidIssue109() {
+        assertEquals(ISSUE_109_ZERO_UUID, UuidUtils.fromUndashed(ISSUE_109_ZERO_UUID_UNDASHED), "UUIDs do not match");
+        assertEquals(ISSUE_109_ZERO_UUID_UNDASHED, UuidUtils.toUndashed(ISSUE_109_ZERO_UUID), "UUIDs do not match");
+    }
+
+    @Test
+    void leadingZeroUuidIssue109() {
+        assertEquals(ISSUE_109_LEADING_ZERO_UUID, UuidUtils.fromUndashed(ISSUE_109_LEADING_ZERO_UNDASHED), "UUIDs do not match");
+        assertEquals(ISSUE_109_LEADING_ZERO_UNDASHED, UuidUtils.toUndashed(ISSUE_109_LEADING_ZERO_UUID), "UUIDs do not match");
+    }
+
+    @Test
+    void oneUuidLsbIssue109() {
+        assertEquals(ISSUE_109_ONE_LSB_UUID, UuidUtils.fromUndashed(ISSUE_109_ONE_LSB_UUID_UNDASHED), "UUIDs do not match");
+        assertEquals(ISSUE_109_ONE_LSB_UUID_UNDASHED, UuidUtils.toUndashed(ISSUE_109_ONE_LSB_UUID), "UUIDs do not match");
+    }
+
+    @Test
+    void oneUuidMsbAndLsbIssue109() {
+        assertEquals(ISSUE_109_ONE_MLSB_UUID, UuidUtils.fromUndashed(ISSUE_109_ONE_MLSB_UUID_UNDASHED), "UUIDs do not match");
+        assertEquals(ISSUE_109_ONE_MLSB_UUID_UNDASHED, UuidUtils.toUndashed(ISSUE_109_ONE_MLSB_UUID), "UUIDs do not match");
+    }
 }