From 884d3aa4ad5a23a0d177a31852f3ac1e5d397f04 Mon Sep 17 00:00:00 2001
From: Sanjay Malakar <iamsanjaymalakar@gmail.com>
Date: Wed, 15 Apr 2026 08:01:52 -0700
Subject: [PATCH] Handle exceptions of individual writers in MultipleWriters
 (#9276)

Ensure all writers are called.
---
 .../zap/extension/script/MultipleWriters.java | 35 ++++++--
 .../script/MultipleWritersUnitTest.java       | 83 +++++++++++++++++++
 2 files changed, 109 insertions(+), 9 deletions(-)
 create mode 100644 zap/src/test/java/org/zaproxy/zap/extension/script/MultipleWritersUnitTest.java

diff --git a/zap/src/main/java/org/zaproxy/zap/extension/script/MultipleWriters.java b/zap/src/main/java/org/zaproxy/zap/extension/script/MultipleWriters.java
index 394bf8358fa..70f97a11a87 100644
--- a/zap/src/main/java/org/zaproxy/zap/extension/script/MultipleWriters.java
+++ b/zap/src/main/java/org/zaproxy/zap/extension/script/MultipleWriters.java
@@ -33,26 +33,43 @@ public class MultipleWriters extends Writer {
 
     private List<Writer> writers = new ArrayList<>();
 
+    @FunctionalInterface
+    private interface WriterAction {
+        void accept(Writer writer) throws IOException;
+    }
+
+    private void forEachWriter(WriterAction action) throws IOException {
+        IOException first = null;
+        for (Writer writer : writers) {
+            try {
+                action.accept(writer);
+            } catch (IOException e) {
+                if (first == null) {
+                    first = e;
+                } else {
+                    first.addSuppressed(e);
+                }
+            }
+        }
+        if (first != null) {
+            throw first;
+        }
+    }
+
     @Override
     public void write(char[] cbuf, int off, int len) throws IOException {
         String str = new String(cbuf, off, len);
-        for (Writer writer : writers) {
-            writer.append(str);
-        }
+        forEachWriter(writer -> writer.append(str));
     }
 
     @Override
     public void flush() throws IOException {
-        for (Writer writer : writers) {
-            writer.flush();
-        }
+        forEachWriter(Writer::flush);
     }
 
     @Override
     public void close() throws IOException {
-        for (Writer writer : writers) {
-            writer.close();
-        }
+        forEachWriter(Writer::close);
     }
 
     public void addWriter(Writer writer) {
diff --git a/zap/src/test/java/org/zaproxy/zap/extension/script/MultipleWritersUnitTest.java b/zap/src/test/java/org/zaproxy/zap/extension/script/MultipleWritersUnitTest.java
new file mode 100644
index 00000000000..cf5a8de7d1f
--- /dev/null
+++ b/zap/src/test/java/org/zaproxy/zap/extension/script/MultipleWritersUnitTest.java
@@ -0,0 +1,83 @@
+/*
+ * Zed Attack Proxy (ZAP) and its related class files.
+ *
+ * ZAP is an HTTP/HTTPS proxy for assessing web application security.
+ *
+ * Copyright 2026 The ZAP Development Team
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.zaproxy.zap.extension.script;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import java.io.IOException;
+import java.io.Writer;
+import org.junit.jupiter.api.Test;
+
+class MultipleWritersUnitTest {
+
+    @Test
+    void shouldWriteToLaterWritersEvenIfEarlierWriterFails() throws Exception {
+        MultipleWriters writers = new MultipleWriters();
+        Writer failingWriter = mock(Writer.class);
+        Writer succeedingWriter = mock(Writer.class);
+
+        doThrow(new IOException("write failed")).when(failingWriter).append("abc");
+
+        writers.addWriter(failingWriter);
+        writers.addWriter(succeedingWriter);
+
+        assertThrows(IOException.class, () -> writers.write("abc".toCharArray(), 0, 3));
+
+        verify(failingWriter).append("abc");
+        verify(succeedingWriter).append("abc");
+    }
+
+    @Test
+    void shouldFlushLaterWritersEvenIfEarlierWriterFails() throws Exception {
+        MultipleWriters writers = new MultipleWriters();
+        Writer failingWriter = mock(Writer.class);
+        Writer succeedingWriter = mock(Writer.class);
+
+        doThrow(new IOException("flush failed")).when(failingWriter).flush();
+
+        writers.addWriter(failingWriter);
+        writers.addWriter(succeedingWriter);
+
+        assertThrows(IOException.class, writers::flush);
+
+        verify(failingWriter).flush();
+        verify(succeedingWriter).flush();
+    }
+
+    @Test
+    void shouldCloseLaterWritersEvenIfEarlierWriterFails() throws Exception {
+        MultipleWriters writers = new MultipleWriters();
+        Writer failingWriter = mock(Writer.class);
+        Writer succeedingWriter = mock(Writer.class);
+
+        doThrow(new IOException("close failed")).when(failingWriter).close();
+
+        writers.addWriter(failingWriter);
+        writers.addWriter(succeedingWriter);
+
+        assertThrows(IOException.class, writers::close);
+
+        verify(failingWriter).close();
+        verify(succeedingWriter).close();
+    }
+}