Netty4HeadersAdapter.remove returns empty list instead of null for non-existing key #36226
Description
Netty4HeadersAdapter implements Map, therefore calling remove("unknown key") should return null, but it doesn't.
The reason is that the method first delegates to io.netty.handler.codec.http.HttpHeaders#getAll(java.lang.String) to get any existing values:
Netty however returns an empty list instead of
null for missing keys:https://github.com/netty/netty/blob/a853a399b5dc976b70d457953741419db0cd45fa/codec-http/src/main/java/io/netty/handler/codec/http/HttpHeaders.java#L1282-L1292
Here's a reproducer:
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpHeaders;
import org.junit.jupiter.api.Test;
import org.springframework.http.support.Netty4HeadersAdapter;
import static org.assertj.core.api.Assertions.assertThat;
class Demo22ApplicationTests {
@Test
void reproducer() {
HttpHeaders nettyHeaders = new DefaultHttpHeaders()
.add("known", "value1")
.add("known", "value2");
Netty4HeadersAdapter adapter = new Netty4HeadersAdapter(nettyHeaders);
assertThat(adapter.remove("known")).containsExactly("value1", "value2"); // succeeds
assertThat(adapter.remove("unknown")).isNull(); // fails with `expected: null but was []`
}
}