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Fix ObjectOutput handling of top-level scalar responses #3861

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Fix ObjectOutput handling of top-level scalar responses #3861

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6d23719
fix: handle top-level object output scalars
cfcromn Jul 23, 2026
10efdc9
Return top-level RESP3 scalar values directly
cfcromn Jul 24, 2026
eb1b5c0
Add regression tests for top-level RESP3 scalar output
cfcromn Jul 24, 2026
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10 changes: 5 additions & 5 deletions src/main/java/io/lettuce/core/output/ObjectOutput.java
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Original file line number Diff line number Diff line change
Expand Up @@ -42,11 +42,6 @@ public ObjectOutput(RedisCodec<K, V> codec) {

@Override
public void set(long integer) {

if (!initialized) {
output = new ArrayList<>();
}

setValue(integer);
}

Expand Down Expand Up @@ -78,6 +73,11 @@ public void setSingle(ByteBuffer bytes) {
@SuppressWarnings("unchecked")
private void setValue(Object value) {

if (!initialized) {
output = new ArrayList<>();

@a-TODO-rov a-TODO-rov Jul 24, 2026

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Shouldn't we assign the actual value here ?

@cfcromn cfcromn Jul 24, 2026

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Thanks! Updated accordingly.

Top-level RESP3 scalar values are now assigned directly to output instead of being wrapped in a List.

@zhengjiudan zhengjiudan Jul 24, 2026

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If value is non-collection type, could we not initialize output as a List? Instead, just assign value to ouput?

@cfcromn cfcromn Jul 24, 2026

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Thanks for the suggestion!

Updated the implementation to assign top-level non-collection RESP3 values directly to output.

Nested collection responses are unchanged because multi() / multiMap() still initialize the collection container before nested values are accumulated.

I also added regression tests covering top-level bulk string, boolean, double, and integer responses.

initialized = true;
}

if (output != null) {

if (output instanceof Collection) {
Expand Down
42 changes: 42 additions & 0 deletions src/test/java/io/lettuce/core/output/ObjectOutputUnitTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import static io.lettuce.TestTags.UNIT_TEST;
import static org.assertj.core.api.Assertions.*;

import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Map;

Expand All @@ -22,6 +23,47 @@
@Tag(UNIT_TEST)
class ObjectOutputUnitTests {

@Test
void shouldParseTopLevelBulkString() {

String in = "$4\r\ntrue\r\n";
RedisStateMachine rsm = new RedisStateMachine(ByteBufAllocator.DEFAULT);
ObjectOutput<String, String> output = new ObjectOutput<>(StringCodec.UTF8);
rsm.decode(Unpooled.wrappedBuffer(in.getBytes(StandardCharsets.UTF_8)), output, exception -> {
throw (RuntimeException) exception;
});
assertThat(output.get()).isInstanceOf(List.class);
assertThat((List) output.get()).containsExactly("true");
}

@Test
void shouldParseTopLevelBoolean() {

RedisStateMachine rsm = new RedisStateMachine(ByteBufAllocator.DEFAULT);
ObjectOutput<String, String> output = new ObjectOutput<>(StringCodec.UTF8);
rsm.decode(Unpooled.wrappedBuffer("#t\r\n".getBytes(StandardCharsets.UTF_8)), output, exception -> {
throw (RuntimeException) exception;
});
rsm.decode(Unpooled.wrappedBuffer("#f\r\n".getBytes(StandardCharsets.UTF_8)), output, exception -> {
throw (RuntimeException) exception;
});
assertThat(output.get()).isInstanceOf(List.class);
assertThat((List) output.get()).containsExactly(true, false);
}

@Test
void shouldParseTopLevelDouble() {

String in = ",1.5\r\n";
RedisStateMachine rsm = new RedisStateMachine(ByteBufAllocator.DEFAULT);
ObjectOutput<String, String> output = new ObjectOutput<>(StringCodec.UTF8);
rsm.decode(Unpooled.wrappedBuffer(in.getBytes(StandardCharsets.UTF_8)), output, exception -> {
throw (RuntimeException) exception;
});
assertThat(output.get()).isInstanceOf(List.class);
assertThat((List) output.get()).containsExactly(1.5d);
}

@Test
void shouldParseHelloWithModules() {

Expand Down