Truncate tags command clipboard text within 32k string limit

src/main/java/net/neoforged/neoforge/server/command/TagsCommand.java

@@ -11,9 +11,9 @@
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import com.mojang.brigadier.exceptions.Dynamic2CommandExceptionType;
 import com.mojang.brigadier.exceptions.DynamicCommandExceptionType;
+import java.util.Iterator;
 import java.util.Optional;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import net.minecraft.ChatFormatting;
 import net.minecraft.commands.CommandSourceStack;
@@ -51,6 +51,10 @@
  * </ul>
  */
 class TagsCommand {
+    // The limit of how long the clipboard text can be; no more elements are added to the text if they would push it over this limit
+    // This is roughly below 32767, the default limit for UTF-8 strings in FriendlyByteBuf. When adjusting this, make sure to leave
+    // ample room for the explanatory text (see #createMessage() below).
+    private static final long CLIPBOARD_TEXT_LIMIT = 32600;
     private static final long PAGE_SIZE = 8;
     private static final ResourceKey<Registry<Registry<?>>> ROOT_REGISTRY_KEY = ResourceKey.createRegistryKey(ResourceLocation.withDefaultNamespace("root"));
 
@@ -171,16 +175,45 @@ private static MutableComponent createMessage(final MutableComponent header,
             final long currentPage,
             final ChatFormatting elementColor,
             final Supplier<Stream<String>> names) {
-        final String allElementNames = names.get().sorted().collect(Collectors.joining("\n"));
         final long totalPages = (count - 1) / PAGE_SIZE + 1;
         final long actualPage = (long) Mth.clamp(currentPage, 1, totalPages);
 
         MutableComponent containsComponent = Component.translatable(containsText, count);
         if (count > 0) // Highlight the count text, make it clickable, and append page counters
         {
+            final String clipboardText;
+            final StringBuilder clipboardTextBuilder = new StringBuilder();
+            boolean reachedLimit = false;
+            int countedLines = 0;
+
+            Iterator<String> iterator = names.get().sorted().iterator();
+            while (iterator.hasNext()) {
+                final String line = iterator.next();
+                if (clipboardTextBuilder.length() + line.length() > CLIPBOARD_TEXT_LIMIT) {
+                    // The to-be-added line puts us over the limit, so stop adding lines
+                    reachedLimit = true;
+                    break;
+                }
+                clipboardTextBuilder.append(line).append('\n');
+                countedLines++;
+            }
+            // Remove the trailing newline if present
+            if (!clipboardTextBuilder.isEmpty()) {
+                clipboardTextBuilder.deleteCharAt(clipboardTextBuilder.length() - 1);
+            }
+
+            if (reachedLimit) {
+                // Almost went over the limit; add additional info to clipboard text
+                clipboardText = "(Too many entries to fit in clipboard, showing only first " + countedLines + " entries...)" + '\n'
+                        + clipboardTextBuilder + '\n'
+                        + "(..." + (count - countedLines) + " more entries not shown)";
+            } else {
+                clipboardText = clipboardTextBuilder.toString();
+            }
+
             containsComponent = ComponentUtils.wrapInSquareBrackets(containsComponent.withStyle(s -> s
                     .withColor(ChatFormatting.GREEN)
-                    .withClickEvent(new ClickEvent(ClickEvent.Action.COPY_TO_CLIPBOARD, allElementNames))
+                    .withClickEvent(new ClickEvent(ClickEvent.Action.COPY_TO_CLIPBOARD, clipboardText))
                     .withHoverEvent(new HoverEvent(HoverEvent.Action.SHOW_TEXT,
                             Component.translatable(copyHoverText)))));
             containsComponent = Component.translatable("commands.neoforge.tags.page_info",