From f0b9894e48b7c3d35babed960d4fef834fcf2071 Mon Sep 17 00:00:00 2001
From: zzz <zzz@mail.i2p>
Date: Thu, 1 Mar 2018 16:26:31 +0000
Subject: [PATCH] Util: Warn on dubious split() regex

---
 core/java/src/net/i2p/data/DataHelper.java | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/core/java/src/net/i2p/data/DataHelper.java b/core/java/src/net/i2p/data/DataHelper.java
index 5135de3fe2..9f7fef83eb 100644
--- a/core/java/src/net/i2p/data/DataHelper.java
+++ b/core/java/src/net/i2p/data/DataHelper.java
@@ -1951,7 +1951,7 @@ public class DataHelper {
      *  This saves about 10 microseconds (Bulldozer) on subsequent invocations.
      *
      *  @param s non-null
-     *  @param regex non-null
+     *  @param regex non-null, don't forget to enclose multiple choices with []
      *  @throws java.util.regex.PatternSyntaxException unchecked
      *  @since 0.9.24
      */
@@ -1966,7 +1966,7 @@ public class DataHelper {
      *  This saves about 10 microseconds (Bulldozer) on subsequent invocations.
      *
      *  @param s non-null
-     *  @param regex non-null
+     *  @param regex non-null, don't forget to enclose multiple choices with []
      *  @param limit result threshold
      *  @throws java.util.regex.PatternSyntaxException unchecked
      *  @since 0.9.24
@@ -1974,6 +1974,11 @@ public class DataHelper {
     public static String[] split(String s, String regex, int limit) {
         Pattern p = patterns.get(regex);
         if (p == null) {
+            // catches easy mistake, and also swapping the args by mistake
+            if (regex.length() > 1 && !regex.startsWith("[") && !regex.equals("\r\n")) {
+                //(new Exception("Warning: Split on regex: \"" + regex + "\" should probably be enclosed with []")).printStackTrace();
+                System.out.println("Warning: Split on regex: \"" + regex + "\" should probably be enclosed with []");
+            }
             p = Pattern.compile(regex);
             patterns.putIfAbsent(regex, p);
         }