Fix bug for accept wildcard case in GraphqlService (#3898)

Motivation:

If `accept` is a wildcard in GraphqlService it won't work.

Modifications:

- Fix `GraphqlUtil`

Result:

- Fix bug

graphql-protocol/src/main/java/com/linecorp/armeria/internal/server/graphql/protocol/GraphqlUtil.java

@@ -57,6 +57,9 @@ public static MediaType produceType(RequestHeaders headers) {
         }
 
         for (MediaType accept : acceptTypes) {
+            if (MediaType.ANY_TYPE.is(accept) || MediaType.ANY_APPLICATION_TYPE.is(accept)) {
+                return MediaType.GRAPHQL_JSON;
+            }
             if (accept.is(MediaType.GRAPHQL_JSON) || accept.is(MediaType.JSON)) {
                 return accept;
             }

graphql-protocol/src/test/java/com/linecorp/armeria/internal/server/graphql/protocol/GraphqlUtilTest.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2021 LINE Corporation
+ *
+ * LINE Corporation licenses this file to you 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:
+ *
+ *   https://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 com.linecorp.armeria.internal.server.graphql.protocol;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.stream.Stream;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import com.linecorp.armeria.common.HttpMethod;
+import com.linecorp.armeria.common.MediaType;
+import com.linecorp.armeria.common.RequestHeaders;
+
+class GraphqlUtilTest {
+
+    @ParameterizedTest
+    @MethodSource("provideMediaType")
+    void test(RequestHeaders requestHeaders, MediaType actual) {
+        final MediaType expected = GraphqlUtil.produceType(requestHeaders);
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    private static Stream<Arguments> provideMediaType() {
+        return Stream.of(
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.ANY_TYPE)
+                                           .build(),
+                             MediaType.GRAPHQL_JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.ANY_APPLICATION_TYPE)
+                                           .build(),
+                             MediaType.GRAPHQL_JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.JSON)
+                                           .build(),
+                             MediaType.JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.GRAPHQL_JSON)
+                                           .build(),
+                             MediaType.GRAPHQL_JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           // accept is null
+                                           .build(),
+                             MediaType.GRAPHQL_JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.GRAPHQL)
+                                           .build(),
+                             null),
+                Arguments.of(RequestHeaders.builder(HttpMethod.GET, "/graphql")
+                                           .contentType(MediaType.ANY_TYPE)
+                                           .accept(MediaType.ANY_TEXT_TYPE)
+                                           .build(),
+                             null),
+                Arguments.of(RequestHeaders.builder(HttpMethod.POST, "/graphql")
+                                           .contentType(MediaType.GRAPHQL)
+                                           .accept(MediaType.GRAPHQL_JSON)
+                                           .build(),
+                             MediaType.GRAPHQL_JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.POST, "/graphql")
+                                           .contentType(MediaType.JSON)
+                                           .accept(MediaType.JSON)
+                                           .build(),
+                             MediaType.JSON),
+                Arguments.of(RequestHeaders.builder(HttpMethod.POST, "/graphql")
+                                           .contentType(MediaType.JSON)
+                                           .accept(MediaType.GRAPHQL_JSON)
+                                           .build(),
+                             MediaType.GRAPHQL_JSON)
+        );
+    }
+}