fix NPE in recursive filtering. BZ 41086.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@481041 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -28,6 +28,9 @@ Fixed bugs:
 * dependset failed if the basedir of a target fileset did not exist.
   Bugzilla 40916.
 
+* Recursive filtering encountered NullPointerExceptions under certain
+  circumstances.  Bugzilla 41086.
+
 Other changes:
 --------------
 

src/main/org/apache/tools/ant/types/FilterSet.java

@@ -581,8 +581,8 @@ public class FilterSet extends DataType implements Cloneable {
         }
         passedTokens.addElement(parent);
         String value = iReplaceTokens(line);
-        if (value.indexOf(beginToken) == -1 && !duplicateToken) {
-            duplicateToken = false;
+        if (value.indexOf(beginToken) == -1 && !duplicateToken
+                && recurseDepth == 1) {
             passedTokens = null;
         } else if (duplicateToken) {
             // should always be the case...

src/tests/antunit/types/filterset-test.xml

@@ -0,0 +1,28 @@
+<project xmlns:au="antlib:org.apache.ant.antunit">
+
+  <property name="br" value="${line.separator}" />
+
+  <target name="testRecursionRegression">
+    <copy todir="${basedir}">
+      <string value="@a@${br}@b@${br}@c@${br}" />
+      <mergemapper to="filterset-output.txt" />
+      <filterset>
+        <filter token="a" value="aaa" />
+        <filter token="b" value="bbb" />
+        <filter token="c" value="@a@:@b@" />
+      </filterset>
+    </copy>
+
+    <au:assertTrue>
+      <resourcesmatch astext="true">
+        <file file="filterset-output.txt" />
+        <string value="aaa${br}bbb${br}aaa:bbb${br}" />
+      </resourcesmatch>
+    </au:assertTrue>
+  </target>
+
+  <target name="tearDown">
+    <delete file="filterset-output.txt" />
+  </target>
+
+</project>