From b7336a40834fabcc325b636c543e2c30ee9099da Mon Sep 17 00:00:00 2001
From: MukjepScarlet <93977077+mukjepscarlet@users.noreply.github.com>
Date: Thu, 23 Oct 2025 15:53:39 +0800
Subject: [PATCH 1/2] Make AppendableWriter do flush and close if delegation
 object supports

---
 .../java/com/google/gson/internal/Streams.java     | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/gson/src/main/java/com/google/gson/internal/Streams.java b/gson/src/main/java/com/google/gson/internal/Streams.java
index 46df853f5a..b46dfe2a70 100644
--- a/gson/src/main/java/com/google/gson/internal/Streams.java
+++ b/gson/src/main/java/com/google/gson/internal/Streams.java
@@ -26,7 +26,9 @@
 import com.google.gson.stream.JsonToken;
 import com.google.gson.stream.JsonWriter;
 import com.google.gson.stream.MalformedJsonException;
+import java.io.Closeable;
 import java.io.EOFException;
+import java.io.Flushable;
 import java.io.IOException;
 import java.io.Writer;
 import java.util.Objects;
@@ -89,10 +91,18 @@ public void write(char[] chars, int offset, int length) throws IOException {
     }
 
     @Override
-    public void flush() {}
+    public void flush() throws IOException {
+      if (appendable instanceof Flushable) {
+        ((Flushable) appendable).flush();
+      }
+    }
 
     @Override
-    public void close() {}
+    public void close() throws IOException {
+      if (appendable instanceof Closeable) {
+        ((Closeable) appendable).close();
+      }
+    }
 
     // Override these methods for better performance
     // They would otherwise unnecessarily create Strings or char arrays

From 855215bbd9bb7360e1e3251cdb2f38f5ae283ddc Mon Sep 17 00:00:00 2001
From: MukjepScarlet <93977077+mukjepscarlet@users.noreply.github.com>
Date: Thu, 23 Oct 2025 16:06:23 +0800
Subject: [PATCH 2/2] Add test

---
 .../com/google/gson/internal/StreamsTest.java | 50 ++++++++++++++++++-
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/gson/src/test/java/com/google/gson/internal/StreamsTest.java b/gson/src/test/java/com/google/gson/internal/StreamsTest.java
index 049a7ee0a1..93f3e5d027 100644
--- a/gson/src/test/java/com/google/gson/internal/StreamsTest.java
+++ b/gson/src/test/java/com/google/gson/internal/StreamsTest.java
@@ -19,15 +19,59 @@
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertThrows;
 
+import java.io.Closeable;
+import java.io.Flushable;
 import java.io.IOException;
 import java.io.Writer;
 import org.junit.Test;
 
 public class StreamsTest {
+  private static class TestAppendable implements Appendable, Flushable, Closeable {
+    boolean closed = false;
+    int flushCount = 0;
+    Appendable append;
+
+    TestAppendable(Appendable append) {
+      this.append = append;
+    }
+
+    @Override
+    public void close() {
+      closed = true;
+    }
+
+    @Override
+    public void flush() {
+      flushCount++;
+    }
+
+    @Override
+    public TestAppendable append(CharSequence csq) throws IOException {
+      append.append(csq);
+      return this;
+    }
+
+    @Override
+    public TestAppendable append(CharSequence csq, int start, int end) throws IOException {
+      append.append(csq, start, end);
+      return this;
+    }
+
+    @Override
+    public TestAppendable append(char c) throws IOException {
+      append.append(c);
+      return this;
+    }
+  }
+
   @Test
   public void testWriterForAppendable() throws IOException {
     StringBuilder stringBuilder = new StringBuilder();
-    Writer writer = Streams.writerForAppendable(stringBuilder);
+    TestAppendable appendable = new TestAppendable(stringBuilder);
+    Writer writer = Streams.writerForAppendable(appendable);
+
+    assertThat(appendable.closed).isFalse();
+    assertThat(appendable.flushCount).isEqualTo(0);
 
     writer.append('a');
     writer.append('\u1234');
@@ -62,7 +106,9 @@ public void testWriterForAppendable() throws IOException {
     writer.flush();
     writer.close();
 
-    // flush() and close() calls should have had no effect
+    assertThat(appendable.closed).isTrue();
+    assertThat(appendable.flushCount).isEqualTo(1);
+
     assertThat(stringBuilder.toString()).isEqualTo(actualOutput);
   }
 }