fix(key): Use String#intern in KeyImpl

Used to save on memory usage with the same key objects created, a better option than using a key pool, and should be faster to compute #equals by reference checks for long-lived keys.

Also pull out internal property API into properties package to use a shared lib.

Author: kermandev

api/build.gradle.kts

@@ -14,6 +14,7 @@ dependencies {
   api(libs.examination.api)
   api(libs.examination.string)
   compileOnlyApi(libs.jetbrainsAnnotations)
+  implementation(projects.adventureProperties)
   testImplementation(libs.guava)
   annotationProcessor(projects.adventureAnnotationProcessors)
   testCompileOnly(libs.autoService.annotations)

key/build.gradle.kts

@@ -12,6 +12,7 @@ dependencies {
   api(libs.examination.api)
   api(libs.examination.string)
   compileOnlyApi(libs.jetbrainsAnnotations)
+  implementation(projects.adventureProperties)
   testImplementation(libs.guava)
 }
 

key/src/main/java/net/kyori/adventure/key/KeyImpl.java

@@ -29,6 +29,7 @@
 import java.util.Objects;
 import java.util.OptionalInt;
 import java.util.stream.Stream;
+import net.kyori.adventure.internal.properties.AdventureProperties;
 import net.kyori.examination.ExaminableProperty;
 import org.intellij.lang.annotations.RegExp;
 import org.jetbrains.annotations.NotNull;
@@ -41,14 +42,16 @@ final class KeyImpl implements Key {
   static final @RegExp String NAMESPACE_PATTERN = "[a-z0-9_\\-.]+";
   static final @RegExp String VALUE_PATTERN = "[a-z0-9_\\-./]+";
 
+  static final AdventureProperties.KeyInternStrategy INTERN_STRATEGY = AdventureProperties.KEY_INTERN_STRATEGY.value();
+
   private final String namespace;
   private final String value;
 
   KeyImpl(final @NotNull String namespace, final @NotNull String value) {
     checkError("namespace", namespace, namespace, value, Key.checkNamespace(namespace), NAMESPACE_PATTERN);
     checkError("value", value, namespace, value, Key.checkValue(value), VALUE_PATTERN);
-    this.namespace = requireNonNull(namespace, "namespace");
-    this.value = requireNonNull(value, "value");
+    this.namespace = finalizeNamespace(requireNonNull(namespace, "namespace"));
+    this.value = finalizeValue(requireNonNull(value, "value"));
   }
 
   private static void checkError(final String name, final String checkPart, final String namespace, final String value, final OptionalInt index, final String pattern) {
@@ -66,6 +69,20 @@ private static void checkError(final String name, final String checkPart, final
     }
   }
 
+  private static String finalizeNamespace(final @NotNull String namespace) {
+    if (AdventureProperties.KeyInternStrategy.ALL.equals(INTERN_STRATEGY) || AdventureProperties.KeyInternStrategy.NAMESPACE.equals(INTERN_STRATEGY)) {
+      return namespace.intern();
+    }
+    return namespace;
+  }
+
+  private static String finalizeValue(final @NotNull String value) {
+    if (AdventureProperties.KeyInternStrategy.ALL.equals(INTERN_STRATEGY)) {
+      return value.intern();
+    }
+    return value;
+  }
+
   static boolean allowedInNamespace(final char character) {
     return character == '_' || character == '-' || (character >= 'a' && character <= 'z') || (character >= '0' && character <= '9') || character == '.';
   }

properties/build.gradle.kts

@@ -0,0 +1,10 @@
+plugins {
+  id("adventure.common-conventions")
+}
+
+dependencies {
+  api(libs.examination.api)
+  api(libs.examination.string)
+}
+
+applyJarMetadata("net.kyori.adventure.internal.properties")

api/src/main/java/net/kyori/adventure/internal/properties/AdventureProperties.java renamed to properties/src/main/java/net/kyori/adventure/internal/properties/AdventureProperties.java

@@ -60,6 +60,13 @@ public final class AdventureProperties {
    */
   public static final Property<Boolean> TEXT_WARN_WHEN_LEGACY_FORMATTING_DETECTED = property("text.warnWhenLegacyFormattingDetected", Boolean::parseBoolean, Boolean.FALSE);
 
+  /**
+   * Property for specifying what strategy to use for interning strings in keys.
+   *
+   * @since 4.22.0
+   */
+  public static final Property<KeyInternStrategy> KEY_INTERN_STRATEGY = property("key.internStrategy", KeyInternStrategy::valueOf, KeyInternStrategy.NAMESPACE);
+
   private AdventureProperties() {
   }
 
@@ -94,4 +101,16 @@ public interface Property<T> {
      */
     @Nullable T value();
   }
+
+  /**
+   * The strategy to use for interning strings in keys.
+   *
+   * @since 4.22.0
+   */
+  @ApiStatus.Internal
+  public enum KeyInternStrategy {
+    NONE,
+    NAMESPACE,
+    ALL
+  }
 }

api/src/main/java/net/kyori/adventure/internal/properties/AdventurePropertiesImpl.java renamed to properties/src/main/java/net/kyori/adventure/internal/properties/AdventurePropertiesImpl.java

@@ -37,6 +37,7 @@ sequenceOf(
   "extra-kotlin",
   "key",
   "nbt",
+  "properties",
   "serializer-configurate4",
   "text-logger-slf4j",
   "text-minimessage",