PaperMC/nms-patches/TileEntitySign.patch

--- a/net/minecraft/server/TileEntitySign.java
+++ b/net/minecraft/server/TileEntitySign.java
@@ -21,6 +21,12 @@
             nbttagcompound.setString("Text" + (i + 1), s);
         }
 
+        // CraftBukkit start
+        if (Boolean.getBoolean("convertLegacySigns")) {
+            nbttagcompound.setBoolean("Bukkit.isConverted", true);
+        }
+        // CraftBukkit end
+
         this.i.b(nbttagcompound);
         return nbttagcompound;
     }
@@ -58,14 +64,34 @@
             }
         };
 
+        // CraftBukkit start - Add an option to convert signs correctly
+        // This is done with a flag instead of all the time because
+        // we have no way to tell whether a sign is from 1.7.10 or 1.8
+
+        boolean oldSign = Boolean.getBoolean("convertLegacySigns") && !nbttagcompound.getBoolean("Bukkit.isConverted");
+
         for (int i = 0; i < 4; ++i) {
             String s = nbttagcompound.getString("Text" + (i + 1));
-            IChatBaseComponent ichatbasecomponent = IChatBaseComponent.ChatSerializer.a(s);
+            if (s != null && s.length() > 2048) {
+                s = "\"\"";
+            }
 
             try {
-                this.lines[i] = ChatComponentUtils.filterForDisplay(icommandlistener, ichatbasecomponent, (Entity) null);
-            } catch (CommandException commandexception) {
-                this.lines[i] = ichatbasecomponent;
+                IChatBaseComponent ichatbasecomponent = IChatBaseComponent.ChatSerializer.a(s);
+
+                if (oldSign) {
+                    lines[i] = org.bukkit.craftbukkit.util.CraftChatMessage.fromString(s)[0];
+                    continue;
+                }
+                // CraftBukkit end
+
+                try {
+                    this.lines[i] = ChatComponentUtils.filterForDisplay(icommandlistener, ichatbasecomponent, (Entity) null);
+                } catch (CommandException commandexception) {
+                    this.lines[i] = ichatbasecomponent;
+                }
+            } catch (com.google.gson.JsonParseException jsonparseexception) {
+                this.lines[i] = new ChatComponentText(s);
             }
         }
 
@@ -155,7 +181,14 @@
                 ChatClickable chatclickable = chatmodifier.h();
 
                 if (chatclickable.a() == ChatClickable.EnumClickAction.RUN_COMMAND) {
-                    entityhuman.C_().getCommandHandler().a(icommandlistener, chatclickable.b());
+                    // CraftBukkit start
+                    // entityhuman.C_().getCommandHandler().a(icommandlistener, chatclickable.b());
+                    CommandBlockListenerAbstract.executeSafely(icommandlistener, new org.bukkit.craftbukkit.command.ProxiedNativeCommandSender(
+                            icommandlistener,
+                            new org.bukkit.craftbukkit.command.CraftBlockCommandSender(icommandlistener),
+                            entityhuman.getBukkitEntity()
+                    ), chatclickable.b());
+                    // CraftBukkit end
                 }
             }
         }