From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: mbax <matt@phozop.net>
Date: Mon, 17 Aug 2020 12:17:37 -0400
Subject: [PATCH] Fix regex mistake in CB NBT int deserialization

The existing regex is too open and allows for the absence of any actual
number data, detecting an NBT entry of just the letter "i" in upper or
lower case. This causes a single-character NBT entry to be processed as
an integer ending in "i", passing an empty String to to Integer.parseInt,
triggering an exception in loading the item.

This commit forces numbers to be present prior to the ending "i"
letter.

diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftNBTTagConfigSerializer.java b/src/main/java/org/bukkit/craftbukkit/util/CraftNBTTagConfigSerializer.java
index be9686a4240acf24a9ee022cff6ba848524b4498..1d282b1f3cf968364474ce5700bc95ebc46b9f1c 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftNBTTagConfigSerializer.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftNBTTagConfigSerializer.java
@@ -18,7 +18,7 @@ import org.jetbrains.annotations.NotNull;
 public class CraftNBTTagConfigSerializer {
 
     private static final Pattern ARRAY = Pattern.compile("^\\[.*]");
-    private static final Pattern INTEGER = Pattern.compile("[-+]?(?:0|[1-9][0-9]*)?i", Pattern.CASE_INSENSITIVE);
+    private static final Pattern INTEGER = Pattern.compile("[-+]?(?:0|[1-9][0-9]*)i", Pattern.CASE_INSENSITIVE); // Paper - fix regex
     private static final Pattern DOUBLE = Pattern.compile("[-+]?(?:[0-9]+[.]?|[0-9]*[.][0-9]+)(?:e[-+]?[0-9]+)?d", Pattern.CASE_INSENSITIVE);
     private static final TagParser MOJANGSON_PARSER = new TagParser(new StringReader(""));