SPIGOT-6234: enum classes don't serialize properly when implementing ConfigurationSerializable

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/configuration/file/YamlRepresenter.java

@@ -14,6 +14,9 @@ public class YamlRepresenter extends Representer {
     public YamlRepresenter() {
         this.multiRepresenters.put(ConfigurationSection.class, new RepresentConfigurationSection());
         this.multiRepresenters.put(ConfigurationSerializable.class, new RepresentConfigurationSerializable());
+        // SPIGOT-6234: We could just switch YamlConstructor to extend Constructor rather than SafeConstructor, however there is a very small risk of issues with plugins treating config as untrusted input
+        // So instead we will just allow future plugins to have their enums extend ConfigurationSerializable
+        this.multiRepresenters.remove(Enum.class);
     }
 
     private class RepresentConfigurationSection extends RepresentMap {

paper-api/src/test/java/org/bukkit/configuration/ConfigurationSectionTest.java

@@ -2,11 +2,13 @@ package org.bukkit.configuration;
 
 import static org.junit.Assert.*;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import org.bukkit.Material;
+import org.bukkit.configuration.serialization.ConfigurationSerializable;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.util.Vector;
 import org.junit.Test;
@@ -592,9 +594,18 @@ public abstract class ConfigurationSectionTest {
         assertFalse(section.isConfigurationSection("doesntExist"));
     }
 
-    public enum TestEnum {
+    public enum TestEnum implements ConfigurationSerializable {
         HELLO,
         WORLD,
-        BANANAS
+        BANANAS;
+
+        @Override
+        public Map<String, Object> serialize() {
+            return Collections.singletonMap("variant", this.name());
+        }
+
+        public static TestEnum deserialize(Map<String, Object> map) {
+            return TestEnum.valueOf((String) map.get("variant"));
+        }
     }
 }

paper-api/src/test/java/org/bukkit/configuration/ConfigurationTest.java

@@ -7,10 +7,16 @@ import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Set;
+import org.bukkit.configuration.serialization.ConfigurationSerialization;
 import org.bukkit.util.Vector;
 import org.junit.Test;
 
 public abstract class ConfigurationTest {
+
+    static {
+        ConfigurationSerialization.registerClass(ConfigurationSectionTest.TestEnum.class);
+    }
+
     public abstract Configuration getConfig();
 
     public Map<String, Object> getTestValues() {
@@ -24,6 +30,7 @@ public abstract class ConfigurationTest {
         result.put("vector", new Vector(12345.67, 64, -12345.6789));
         result.put("list", Arrays.asList(1, 2, 3, 4, 5));
         result.put("42", "The Answer");
+        result.put("enum", ConfigurationSectionTest.TestEnum.BANANAS);
 
         return result;
     }

paper-api/src/test/java/org/bukkit/configuration/file/YamlConfigurationTest.java

@@ -38,7 +38,10 @@ public class YamlConfigurationTest extends FileConfigurationTest {
                 + "- 3\n"
                 + "- 4\n"
                 + "- 5\n"
-                + "'42': The Answer\n";
+                + "'42': The Answer\n"
+                + "enum:\n"
+                + "  ==: org.bukkit.configuration.ConfigurationSectionTest$TestEnum\n"
+                + "  variant: BANANAS\n";
     }
 
     @Test