Add Warning API and settings for Deprecated events

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/main/java/org/bukkit/Bukkit.java

@@ -8,6 +8,7 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.logging.Logger;
 
+import org.bukkit.Warning.WarningState;
 import org.bukkit.command.CommandSender;
 import org.bukkit.command.ConsoleCommandSender;
 import org.bukkit.command.PluginCommand;
@@ -373,4 +374,8 @@ public final class Bukkit {
     public static String getMotd() {
         return server.getMotd();
     }
+
+    public static WarningState getWarningState() {
+        return server.getWarningState();
+    }
 }

paper-api/src/main/java/org/bukkit/Server.java

@@ -8,6 +8,7 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.logging.Logger;
 
+import org.bukkit.Warning.WarningState;
 import org.bukkit.command.CommandException;
 import org.bukkit.command.CommandSender;
 import org.bukkit.command.ConsoleCommandSender;
@@ -651,4 +652,11 @@ public interface Server extends PluginMessageRecipient {
      * @returns the servers MOTD
      */
     String getMotd();
+
+    /**
+     * Gets the current warning state for the server
+     *
+     * @return The configured WarningState
+     */
+    public WarningState getWarningState();
 }

paper-api/src/main/java/org/bukkit/Warning.java

@@ -0,0 +1,93 @@
+package org.bukkit;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.Map;
+
+import com.google.common.collect.ImmutableMap;
+
+/**
+ * This designates the warning state for a specific item.
+ * When the server settings dictate 'default' warnings, warnings are printed if the {@link #value()} is true.
+ */
+@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.TYPE})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Warning {
+    /**
+     * This represents the states that server verbose for warnings may be.
+     */
+    public enum WarningState {
+        /**
+         * Indicates all warnings should be printed for deprecated items.
+         */
+        ON,
+        /**
+         * Indicates no warnings should be printed for deprecated items.
+         */
+        OFF,
+        /**
+         * Indicates each warning would default to the configured {@link Warning} annotation, or always if annotation not found.
+         */
+        DEFAULT;
+
+        private static final Map<String, WarningState> values = ImmutableMap.<String,WarningState>builder()
+                .put("off", OFF)
+                .put("false", OFF)
+                .put("f", OFF)
+                .put("no", OFF)
+                .put("n", OFF)
+                .put("on", ON)
+                .put("true", ON)
+                .put("t", ON)
+                .put("yes", ON)
+                .put("y", ON)
+                .put("", DEFAULT)
+                .put("d", DEFAULT)
+                .put("default", DEFAULT)
+                .build();
+
+        /**
+         * This method checks the provided warning should be printed for this state
+         * @param warning The warning annotation added to a deprecated item
+         * @return ON is always True<br>
+         *  OFF is always false<br>
+         *  DEFAULT is false if and only if annotation is not null and specifies false for {@link Warning#value()}, true otherwise.
+         */
+        public boolean printFor(Warning warning) {
+            if (this == DEFAULT) {
+                return warning == null || warning.value();
+            }
+            return this == ON;
+        }
+
+        /**
+         * This method returns the corresponding warning state for the given string value.
+         * @param value The string value to check
+         * @return {@link #DEFAULT} if not found, or the respective WarningState
+         */
+        public static WarningState value(final String value) {
+            if (value == null) {
+                return DEFAULT;
+            }
+            WarningState state = values.get(value.toLowerCase());
+            if (state == null) {
+                return DEFAULT;
+            }
+            return state;
+        }
+    }
+
+    /**
+     * This sets if the deprecation warnings when registering events gets printed when the setting is in the default state.
+     * @return false normally, or true to encourage warning printout
+     */
+    boolean value() default false;
+
+    /**
+     * This can provide detailed information on why the event is deprecated.
+     * @return The reason an event is deprecated
+     */
+    String reason() default "";
+}

paper-api/src/main/java/org/bukkit/event/player/AsyncPlayerChatEvent.java

@@ -10,7 +10,10 @@ import org.bukkit.event.HandlerList;
 /**
  * This event will sometimes fire synchronously, depending on how it was triggered.
  * The constructor provides a boolean to indicate if the event was fired synchronously or asynchronously.
- * If a plugin causes a Player to chat with {@link Player#chat(String)} or by other general means, this event will be synchronous.<br>
+ * When asynchronous, this event can be called from any thread, but the main thread, and has limited access to the API.<br>
+ * <br>
+ * If a player is the direct cause of this event by incoming packet, this event will be asynchronous.
+ * If a plugin triggers this event by compelling a player to chat, this event will be synchronous.<br>
  * <br>
  * <b>Care should be taken to check {@link #isAsynchronous()} and treat the event appropriately.</b>
  */

paper-api/src/main/java/org/bukkit/event/player/PlayerChatEvent.java

@@ -5,17 +5,20 @@ import java.util.HashSet;
 import java.util.Set;
 
 import org.apache.commons.lang.Validate;
+import org.bukkit.Warning;
 import org.bukkit.entity.Player;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.HandlerList;
 
 /**
  * Holds information for player chat and commands
- * @deprecated This event was broken in 1.3, where chat should be asynchronous.
+ * @deprecated This event will fire from the main thread and allows the use of all of the Bukkit API, unlike the {@link AsyncPlayerChatEvent}.<br>
- * It is deprecated because listening for it is detrimental to server performance.
+ *  <br>
- * {@link AsyncPlayerChatEvent} is the encouraged alternative.
+ *  Listening to this event forces chat to wait for the main thread which causes delays for chat.<br>
+ *  {@link AsyncPlayerChatEvent} is the encouraged alternative for thread safe implementations.
  */
 @Deprecated
+@Warning(reason="Listening to this event forces chat to wait for the main thread, delaying chat messages.")
 public class PlayerChatEvent extends PlayerEvent implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
     private boolean cancel = false;

paper-api/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java

@@ -23,6 +23,8 @@ import java.util.regex.Pattern;
 import org.apache.commons.lang.Validate;
 import org.bukkit.Bukkit;
 import org.bukkit.Server;
+import org.bukkit.Warning;
+import org.bukkit.Warning.WarningState;
 import org.bukkit.configuration.serialization.ConfigurationSerializable;
 import org.bukkit.configuration.serialization.ConfigurationSerialization;
 import org.bukkit.event.Event;
@@ -299,16 +301,22 @@ public class JavaPluginLoader implements PluginLoader {
             for (Class<?> clazz = eventClass; Event.class.isAssignableFrom(clazz); clazz = clazz.getSuperclass()) {
                 // This loop checks for extending deprecated events
                 if (clazz.getAnnotation(Deprecated.class) != null) {
+                    Warning warning = clazz.getAnnotation(Warning.class);
+                    WarningState warningState = server.getWarningState();
+                    if (!warningState.printFor(warning)) {
+                        break;
+                    }
                     plugin.getLogger().log(
                             Level.WARNING,
                             String.format(
                                     "\"%s\" has registered a listener for %s on method \"%s\", but the event is Deprecated." +
-                                    " Server performance will be affected; please notify the authors %s.",
+                                    " \"%s\"; please notify the authors %s.",
                                     plugin.getDescription().getFullName(),
                                     clazz.getName(),
                                     method.toGenericString(),
+                                    (warning != null && warning.reason().length() != 0) ? warning.reason() : "Server performance will be affected",
                                     Arrays.toString(plugin.getDescription().getAuthors().toArray())),
-                            new AuthorNagException(null));
+                            warningState == WarningState.ON ? new AuthorNagException(null) : null);
                     break;
                 }
             }