Add workaround for SnakeYAML 100 comment limit

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

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

@@ -0,0 +1,74 @@
+package org.bukkit.configuration.file;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.lang.reflect.Field;
+import java.util.ArrayDeque;
+import java.util.Queue;
+import org.jetbrains.annotations.NotNull;
+import org.yaml.snakeyaml.DumperOptions;
+import org.yaml.snakeyaml.LoaderOptions;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.comments.CommentEventsCollector;
+import org.yaml.snakeyaml.comments.CommentType;
+import org.yaml.snakeyaml.constructor.BaseConstructor;
+import org.yaml.snakeyaml.emitter.Emitter;
+import org.yaml.snakeyaml.error.YAMLException;
+import org.yaml.snakeyaml.events.Event;
+import org.yaml.snakeyaml.nodes.Node;
+import org.yaml.snakeyaml.representer.Representer;
+import org.yaml.snakeyaml.serializer.Serializer;
+
+final class BukkitYaml extends Yaml {
+
+    private static final Field events;
+    private static final Field blockCommentsCollector;
+    private static final Field inlineCommentsCollector;
+
+    private static Field getEmitterField(String name) {
+        Field field = null;
+        try {
+            field = Emitter.class.getDeclaredField(name);
+            field.setAccessible(true);
+        } catch (ReflectiveOperationException ex) {
+            // Ignore as a fail-safe fallback
+        }
+        return field;
+    }
+
+    static {
+        events = getEmitterField("events");
+        blockCommentsCollector = getEmitterField("blockCommentsCollector");
+        inlineCommentsCollector = getEmitterField("inlineCommentsCollector");
+    }
+
+    public BukkitYaml(@NotNull BaseConstructor constructor, @NotNull Representer representer, @NotNull DumperOptions dumperOptions, @NotNull LoaderOptions loadingConfig) {
+        super(constructor, representer, dumperOptions, loadingConfig);
+    }
+
+    @Override
+    public void serialize(@NotNull Node node, @NotNull Writer output) {
+        Emitter emitter = new Emitter(output, dumperOptions);
+        if (events != null && blockCommentsCollector != null && inlineCommentsCollector != null) {
+            Queue<Event> newEvents = new ArrayDeque<>(100);
+
+            try {
+                events.set(emitter, newEvents);
+                blockCommentsCollector.set(emitter, new CommentEventsCollector(newEvents, CommentType.BLANK_LINE, CommentType.BLOCK));
+                inlineCommentsCollector.set(emitter, new CommentEventsCollector(newEvents, CommentType.IN_LINE));
+            } catch (ReflectiveOperationException ex) {
+                // Don't ignore this as we could be in an inconsistent state
+                throw new RuntimeException("Could not update Yaml event queue", ex);
+            }
+        }
+
+        Serializer serializer = new Serializer(emitter, resolver, dumperOptions, null);
+        try {
+            serializer.open();
+            serializer.serialize(node);
+            serializer.close();
+        } catch (IOException ex) {
+            throw new YAMLException(ex);
+        }
+    }
+}

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

@@ -64,7 +64,7 @@ public class YamlConfiguration extends FileConfiguration {
         yamlLoaderOptions = new LoaderOptions();
         yamlLoaderOptions.setMaxAliasesForCollections(Integer.MAX_VALUE); // SPIGOT-5881: Not ideal, but was default pre SnakeYAML 1.26
 
-        yaml = new Yaml(constructor, representer, yamlDumperOptions, yamlLoaderOptions);
+        yaml = new BukkitYaml(constructor, representer, yamlDumperOptions, yamlLoaderOptions);
     }
 
     @NotNull

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

@@ -144,4 +144,23 @@ public class YamlConfigurationTest extends FileConfigurationTest {
                 + "    height-offset: 2\n";
         assertEquals(expected, config.saveToString());
     }
+
+    @Test
+    public void test100Comments() throws InvalidConfigurationException {
+        StringBuilder commentBuilder = new StringBuilder();
+        for (int i = 0; i < 100; i++) {
+            commentBuilder.append("# Comment ").append(i).append("\n");
+        }
+
+        final String data = ""
+                + commentBuilder
+                + "simpleKey: simpleValue\n"
+                + "\n";
+
+        YamlConfiguration config = getConfig();
+        config.loadFromString(data);
+
+        String result = config.saveToString();
+        assertEquals(data, result);
+    }
 }