[CLI-351] Multiple trailing BREAK_CHAR_SET characters cause infinite

garydgregory · garydgregory · commit dcc169b91834 · 2025-09-30T06:51:14.000-04:00
loop in HelpFormatter
diff --git a/src/changes/changes.xml b/src/changes/changes.xml
@@ -24,6 +24,7 @@
   <body>
     <release version="1.10.1" date="YYYY-MM-DD" description="This is a feature and maintenance release. Java 8 or later is required.">
       <!-- FIX -->
+      <action type="fix" issue="CLI-351" dev="ggregory" due-to="Damien Carbonne, Claude Warren, Gary Gregory">Multiple trailing BREAK_CHAR_SET characters cause infinite loop in HelpFormatter.</action>
       <!-- ADD -->
       <!-- UPDATE -->
       <action type="update" dev="ggregory" due-to="Gary Gregory, Dependabot">Bump org.apache.commons:commons-parent from 85 to 88 #393.</action>
diff --git a/src/test/java/org/apache/commons/cli/help/HelpFormatterTest.java b/src/test/java/org/apache/commons/cli/help/HelpFormatterTest.java
@@ -147,6 +147,19 @@ void testPrintHelp() throws IOException {
         assertEquals(0, sb.length(), "Should not write to output");
     }
 
+    /**
+     * Tests example from the mailing list that caused an infinite loop.
+     * 
+     * @see <a href="https://issues.apache.org/jira/browse/CLI-351">[CLI-351] Multiple traililng BREAK_CHAR_SET characters cause infinite loop in
+     *      HelpFormatter</a>
+     */
+    @Test
+    void testPrintHelpHeader() throws IOException {
+        HelpFormatter.builder().get().printHelp("CL syntax", "Header", Collections.emptyList(), "Footer", true);
+        HelpFormatter.builder().get().printHelp("CL syntax", "Header\n\n", // This makes printHelp enter into an infinite loop
+                Collections.emptyList(), "Footer", true);
+    }
+
     @Test
     void testPrintHelpXML() throws IOException {
         final StringBuilder sb = new StringBuilder();
