From c5d0a59894a57911e64a72a7f071fa9bf6a8b72d Mon Sep 17 00:00:00 2001
From: Adam Retter <adam.retter@googlemail.com>
Date: Mon, 10 Apr 2023 15:12:25 +0100
Subject: [PATCH] [bugfix] fn:replace, fn:tokenize, and fn:analyze-string must
 throw FORX0003 when pattern matches an empty string Closes
 https://github.com/eXist-db/exist/issues/3803

---
 .../xquery/functions/fn/FunAnalyzeString.java  |  3 +++
 .../exist/xquery/functions/fn/FunReplace.java  |  3 +++
 exist-core/src/test/xquery/regex.xml           | 18 ++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/exist-core/src/main/java/org/exist/xquery/functions/fn/FunAnalyzeString.java b/exist-core/src/main/java/org/exist/xquery/functions/fn/FunAnalyzeString.java
index 1fd6bc13bc7..870fa3e392a 100644
--- a/exist-core/src/main/java/org/exist/xquery/functions/fn/FunAnalyzeString.java
+++ b/exist-core/src/main/java/org/exist/xquery/functions/fn/FunAnalyzeString.java
@@ -130,6 +130,9 @@ private void analyzeString(final MemTreeBuilder builder, final String input, Str
 
         try {
             final RegularExpression regularExpression = config.compileRegularExpression(pattern, flags, "XP30", warnings);
+            if (regularExpression.matches("")) {
+                throw new XPathException(this, ErrorCodes.FORX0003, "regular expression could match empty string");
+            }
 
             //TODO(AR) cache the regular expression... might be possible through Saxon config
 
diff --git a/exist-core/src/main/java/org/exist/xquery/functions/fn/FunReplace.java b/exist-core/src/main/java/org/exist/xquery/functions/fn/FunReplace.java
index 258d339fbfe..7707ee1700a 100644
--- a/exist-core/src/main/java/org/exist/xquery/functions/fn/FunReplace.java
+++ b/exist-core/src/main/java/org/exist/xquery/functions/fn/FunReplace.java
@@ -120,6 +120,9 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
 
 			try {
 				final RegularExpression regularExpression = config.compileRegularExpression(pattern, flags, "XP30", warnings);
+				if (regularExpression.matches("")) {
+					throw new XPathException(this, ErrorCodes.FORX0003, "regular expression could match empty string");
+				}
 
 				//TODO(AR) cache the regular expression... might be possible through Saxon config
 
diff --git a/exist-core/src/test/xquery/regex.xml b/exist-core/src/test/xquery/regex.xml
index 2f56a19d51c..349abe6f16c 100644
--- a/exist-core/src/test/xquery/regex.xml
+++ b/exist-core/src/test/xquery/regex.xml
@@ -121,6 +121,12 @@
         <expected>lo</expected>
     </test>
 
+    <test output="text">
+        <task>fn:replace-regex-match-empty-1</task>
+        <code>fn:replace("12.34" , "^\D*", "")</code>
+        <error>FORX0003</error>
+    </test>
+
     <test output="text">
         <task>fn:tokenize-qflag-1</task>
         <code>fn:tokenize("12.3.5.6", ".", "q")</code>
@@ -139,4 +145,16 @@
         <error>XPTY0004</error>
     </test>
 
+    <test output="text">
+        <task>fn:tokenize-regex-match-empty-1</task>
+        <code>fn:tokenize("12.34" , "^\D*")</code>
+        <error>FORX0003</error>
+    </test>
+
+    <test output="text">
+        <task>fn:analyze-string-regex-match-empty-1</task>
+        <code>fn:analyze-string("12.34" , "^\D*")</code>
+        <error>FORX0003</error>
+    </test>
+
 </TestSet>
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