Add auto-save plugin redundancy detection.

This change will print a warning when a plugin induces a forced save. A
player or console forcing a save (via a command) is ignored for purposes
of printing a warning.

src/main/java/net/minecraft/server/PlayerConnection.java

@@ -831,7 +831,16 @@ public class PlayerConnection extends Connection {
                     return;
                 }
 
+                if (!packet3chat.a_()) {
+                    try {
+                        this.minecraftServer.server.playerCommandState = true;
                         this.chat(s, packet3chat.a_());
+                    } finally {
+                        this.minecraftServer.server.playerCommandState = false;
+                    }
+                } else {
+                    this.chat(s, packet3chat.a_());
+                }
 
                 // This section stays because it is only applicable to packets
                 if (chatSpamField.addAndGet(this, 20) > 200 && !this.minecraftServer.getPlayerList().isOp(this.player.getName())) { // CraftBukkit use thread-safe spam

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -162,6 +162,8 @@ public final class CraftServer implements Server {
     private WarningState warningState = WarningState.DEFAULT;
     private final BooleanWrapper online = new BooleanWrapper();
     public CraftScoreboardManager scoreboardManager;
+    public boolean playerCommandState;
+    private boolean printSaveWarning;
 
     private final class BooleanWrapper {
         private boolean value = true;
@@ -509,10 +511,13 @@ public final class CraftServer implements Server {
             }
         }
         try {
+            this.playerCommandState = true;
             return dispatchCommand(sender, serverCommand.command);
         } catch (Exception ex) {
             getLogger().log(Level.WARNING, "Unexpected exception while parsing console command \"" + serverCommand.command + '"', ex);
             return false;
+        } finally {
+            this.playerCommandState = false;
         }
     }
 
@@ -553,6 +558,7 @@ public final class CraftServer implements Server {
         waterAnimalSpawn = configuration.getInt("spawn-limits.water-animals");
         ambientSpawn = configuration.getInt("spawn-limits.ambient");
         warningState = WarningState.value(configuration.getString("settings.deprecated-verbose"));
+        printSaveWarning = false;
         console.autosavePeriod = configuration.getInt("ticks-per.autosave");
         chunkGCPeriod = configuration.getInt("chunk-gc.period-in-ticks");
         chunkGCLoadThresh = configuration.getInt("chunk-gc.load-threshold");
@@ -862,6 +868,7 @@ public final class CraftServer implements Server {
     }
 
     public void savePlayers() {
+        checkSaveState();
         playerList.savePlayers();
     }
 
@@ -1374,4 +1381,12 @@ public final class CraftServer implements Server {
     public CraftScoreboardManager getScoreboardManager() {
         return scoreboardManager;
     }
+
+    public void checkSaveState() {
+        if (this.playerCommandState || this.printSaveWarning || this.console.autosavePeriod <= 0) {
+            return;
+        }
+        this.printSaveWarning = true;
+        getLogger().log(Level.WARNING, "A manual (plugin-induced) save has been detected while server is configured to auto-save. This may affect performance.", warningState == WarningState.ON ? new Throwable() : null);
+    }
 }

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -641,6 +641,7 @@ public class CraftWorld implements World {
     }
 
     public void save() {
+        this.server.checkSaveState();
         try {
             boolean oldSave = world.savingDisabled;