Return covariant future types from session async methods

Motivation:

We experienced problems by the past trying to extend classes and
override methods returning CompletionStage<SomeInterface>. It is
usually better to return CompletionStage<? extends SomeInterface> since
this can be overridden by CompletionStage<? extends SomeChildInterface>
thanks to type covariance.

We modified lots of methods but for some reason we forgot a few ones in
CqlSession and DefaultSession.

Modifications:

- Modify return types of methods in CqlSession and DefaultSession from
  CompletionStage<T> to CompletionStage<? extends T>.

Result:

Methods in CqlSession and DefaultSession can now be overriden more
easily.

Author: adutra

core/revapi.json

@@ -522,6 +522,81 @@
         "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
         "elementKind": "method",
         "justification": "Add ability to query specific nodes for virtual tables"
+      },
+      {
+        "code": "java.method.returnTypeTypeParametersChanged",
+        "old": "method java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.AsyncResultSet> com.datastax.oss.driver.api.core.CqlSession::executeAsync(com.datastax.oss.driver.api.core.cql.Statement<?>)",
+        "new": "method java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.AsyncResultSet> com.datastax.oss.driver.api.core.CqlSession::executeAsync(com.datastax.oss.driver.api.core.cql.Statement<?>)",
+        "oldType": "java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.AsyncResultSet>",
+        "newType": "java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.AsyncResultSet>",
+        "package": "com.datastax.oss.driver.api.core",
+        "classQualifiedName": "com.datastax.oss.driver.api.core.CqlSession",
+        "classSimpleName": "CqlSession",
+        "methodName": "executeAsync",
+        "oldArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta1",
+        "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
+        "elementKind": "method",
+        "justification": "Return covariant future types from session async methods"
+      },
+      {
+        "code": "java.method.returnTypeTypeParametersChanged",
+        "old": "method java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.AsyncResultSet> com.datastax.oss.driver.api.core.CqlSession::executeAsync(java.lang.String)",
+        "new": "method java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.AsyncResultSet> com.datastax.oss.driver.api.core.CqlSession::executeAsync(java.lang.String)",
+        "oldType": "java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.AsyncResultSet>",
+        "newType": "java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.AsyncResultSet>",
+        "package": "com.datastax.oss.driver.api.core",
+        "classQualifiedName": "com.datastax.oss.driver.api.core.CqlSession",
+        "classSimpleName": "CqlSession",
+        "methodName": "executeAsync",
+        "oldArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta1",
+        "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
+        "elementKind": "method",
+        "justification": "Return covariant future types from session async methods"
+      },
+      {
+        "code": "java.method.returnTypeTypeParametersChanged",
+        "old": "method java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(com.datastax.oss.driver.api.core.cql.PrepareRequest)",
+        "new": "method java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(com.datastax.oss.driver.api.core.cql.PrepareRequest)",
+        "oldType": "java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "newType": "java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "package": "com.datastax.oss.driver.api.core",
+        "classQualifiedName": "com.datastax.oss.driver.api.core.CqlSession",
+        "classSimpleName": "CqlSession",
+        "methodName": "prepareAsync",
+        "oldArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta1",
+        "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
+        "elementKind": "method",
+        "justification": "Return covariant future types from session async methods"
+      },
+      {
+        "code": "java.method.returnTypeTypeParametersChanged",
+        "old": "method java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(com.datastax.oss.driver.api.core.cql.SimpleStatement)",
+        "new": "method java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(com.datastax.oss.driver.api.core.cql.SimpleStatement)",
+        "oldType": "java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "newType": "java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "package": "com.datastax.oss.driver.api.core",
+        "classQualifiedName": "com.datastax.oss.driver.api.core.CqlSession",
+        "classSimpleName": "CqlSession",
+        "methodName": "prepareAsync",
+        "oldArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta1",
+        "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
+        "elementKind": "method",
+        "justification": "Return covariant future types from session async methods"
+      },
+      {
+        "code": "java.method.returnTypeTypeParametersChanged",
+        "old": "method java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(java.lang.String)",
+        "new": "method java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement> com.datastax.oss.driver.api.core.CqlSession::prepareAsync(java.lang.String)",
+        "oldType": "java.util.concurrent.CompletionStage<com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "newType": "java.util.concurrent.CompletionStage<? extends com.datastax.oss.driver.api.core.cql.PreparedStatement>",
+        "package": "com.datastax.oss.driver.api.core",
+        "classQualifiedName": "com.datastax.oss.driver.api.core.CqlSession",
+        "classSimpleName": "CqlSession",
+        "methodName": "prepareAsync",
+        "oldArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta1",
+        "newArchive": "com.datastax.oss:java-driver-core:jar:4.0.0-beta2-SNAPSHOT",
+        "elementKind": "method",
+        "justification": "Return covariant future types from session async methods"
       }
     ]
   }

core/src/main/java/com/datastax/oss/driver/api/core/CqlSession.java

@@ -61,7 +61,7 @@ default ResultSet execute(@NonNull String query) {
    * generally before the result is available).
    */
   @NonNull
-  default CompletionStage<AsyncResultSet> executeAsync(@NonNull Statement<?> statement) {
     return Objects.requireNonNull(
         execute(statement, Statement.ASYNC), "The CQL processor should never return a null result");
   }
@@ -71,7 +71,7 @@ default CompletionStage<AsyncResultSet> executeAsync(@NonNull Statement<?> state
    * generally before the result is available).
    */
   @NonNull
-  default CompletionStage<AsyncResultSet> executeAsync(@NonNull String query) {
     return executeAsync(SimpleStatement.newInstance(query));
   }
 
@@ -167,7 +167,8 @@ default PreparedStatement prepare(@NonNull PrepareRequest request) {
    * details.
    */
   @NonNull
-  default CompletionStage<PreparedStatement> prepareAsync(@NonNull SimpleStatement statement) {
+      @NonNull SimpleStatement statement) {
     return Objects.requireNonNull(
         execute(new DefaultPrepareRequest(statement), PrepareRequest.ASYNC),
         "The CQL prepare processor should never return a null result");
@@ -178,7 +179,7 @@ default CompletionStage<PreparedStatement> prepareAsync(@NonNull SimpleStatement
    * sent, generally before the statement is prepared).
    */
   @NonNull
-  default CompletionStage<PreparedStatement> prepareAsync(@NonNull String query) {
     return Objects.requireNonNull(
         execute(new DefaultPrepareRequest(query), PrepareRequest.ASYNC),
         "The CQL prepare processor should never return a null result");
@@ -194,7 +195,7 @@ default CompletionStage<PreparedStatement> prepareAsync(@NonNull String query) {
    * with {@link PrepareRequest} directly.
    */
   @NonNull
-  default CompletionStage<PreparedStatement> prepareAsync(PrepareRequest request) {
     return Objects.requireNonNull(
         execute(request, PrepareRequest.ASYNC),
         "The CQL prepare processor should never return a null result");

core/src/main/java/com/datastax/oss/driver/internal/core/cql/DefaultAsyncResultSet.java

@@ -95,7 +95,7 @@ public boolean hasMorePages() {
 
   @NonNull
   @Override
-  public CompletionStage<AsyncResultSet> fetchNextPage() throws IllegalStateException {
     ByteBuffer nextState = executionInfo.getPagingState();
     if (nextState == null) {
       throw new IllegalStateException(

core/src/main/java/com/datastax/oss/driver/internal/core/session/DefaultSession.java

@@ -128,13 +128,13 @@ public boolean isSchemaMetadataEnabled() {
 
   @NonNull
   @Override
-  public CompletionStage<Metadata> setSchemaMetadataEnabled(@Nullable Boolean newValue) {
     return metadataManager.setSchemaEnabled(newValue);
   }
 
   @NonNull
   @Override
-  public CompletionStage<Metadata> refreshSchemaAsync() {
     return metadataManager.refreshSchema(null, true, true);
   }
 

core/src/test/java/com/datastax/oss/driver/internal/core/cql/DefaultAsyncResultSetTest.java

@@ -55,7 +55,7 @@ public class DefaultAsyncResultSetTest {
   public void setup() {
     MockitoAnnotations.initMocks(this);
 
-    Mockito.when(executionInfo.getStatement()).thenReturn((Statement) statement);
     Mockito.when(context.getCodecRegistry()).thenReturn(CodecRegistry.DEFAULT);
     Mockito.when(context.getProtocolVersion()).thenReturn(DefaultProtocolVersion.DEFAULT);
   }
@@ -85,14 +85,15 @@ public void should_invoke_session_to_fetch_next_page() {
     Mockito.when(((Statement) statement).copy(mockPagingState)).thenReturn(mockNextStatement);
 
     CompletableFuture<AsyncResultSet> mockResultFuture = new CompletableFuture<>();
-    Mockito.when(session.executeAsync(Mockito.any(Statement.class))).thenReturn(mockResultFuture);
+        .thenAnswer(invocation -> mockResultFuture);
 
     // When
     DefaultAsyncResultSet resultSet =
         new DefaultAsyncResultSet(
             columnDefinitions, executionInfo, new ArrayDeque<>(), session, context);
     assertThat(resultSet.hasMorePages()).isTrue();
-    CompletionStage<AsyncResultSet> nextPageFuture = resultSet.fetchNextPage();
 
     // Then
     Mockito.verify(statement).copy(mockPagingState);

core/src/test/java/com/datastax/oss/driver/internal/core/cql/QueryTraceFetcherTest.java

@@ -116,7 +116,8 @@ public void should_succeed_when_both_queries_succeed_immediately() {
     CompletionStage<AsyncResultSet> sessionRow = completeSessionRow();
     CompletionStage<AsyncResultSet> eventRows = singlePageEventRows();
     Mockito.when(session.executeAsync(any(SimpleStatement.class)))
-        .thenReturn(sessionRow, eventRows);
+        .thenAnswer(invocation -> eventRows);
 
     // When
     QueryTraceFetcher fetcher = new QueryTraceFetcher(TRACING_ID, session, context, config);
@@ -167,7 +168,9 @@ public void should_succeed_when_events_query_is_paged() {
     CompletionStage<AsyncResultSet> eventRows1 = multiPageEventRows1();
     CompletionStage<AsyncResultSet> eventRows2 = multiPageEventRows2();
     Mockito.when(session.executeAsync(any(SimpleStatement.class)))
-        .thenReturn(sessionRow, eventRows1, eventRows2);
+        .thenAnswer(invocation -> eventRows1)
+        .thenAnswer(invocation -> eventRows2);
 
     // When
     QueryTraceFetcher fetcher = new QueryTraceFetcher(TRACING_ID, session, context, config);
@@ -192,7 +195,9 @@ public void should_retry_when_session_row_is_incomplete() {
     CompletionStage<AsyncResultSet> sessionRow2 = completeSessionRow();
     CompletionStage<AsyncResultSet> eventRows = singlePageEventRows();
     Mockito.when(session.executeAsync(any(SimpleStatement.class)))
-        .thenReturn(sessionRow1, sessionRow2, eventRows);
+        .thenAnswer(invocation -> sessionRow2)
+        .thenAnswer(invocation -> eventRows);
 
     // When
     QueryTraceFetcher fetcher = new QueryTraceFetcher(TRACING_ID, session, context, config);
@@ -259,7 +264,9 @@ public void should_fail_when_session_query_still_incomplete_after_max_tries() {
     CompletionStage<AsyncResultSet> sessionRow2 = incompleteSessionRow();
     CompletionStage<AsyncResultSet> sessionRow3 = incompleteSessionRow();
     Mockito.when(session.executeAsync(any(SimpleStatement.class)))
-        .thenReturn(sessionRow1, sessionRow2, sessionRow3);
+        .thenAnswer(invocation -> sessionRow2)
+        .thenAnswer(invocation -> sessionRow3);
 
     // When
     QueryTraceFetcher fetcher = new QueryTraceFetcher(TRACING_ID, session, context, config);

integration-tests/src/test/java/com/datastax/oss/driver/api/core/connection/FrameLengthIT.java

@@ -92,7 +92,7 @@ public void should_fail_if_request_exceeds_max_frame_length() {
 
   @Test
   public void should_fail_if_response_exceeds_max_frame_length() {
-    CompletionStage<AsyncResultSet> slowResultFuture =
         sessionRule.session().executeAsync(SLOW_QUERY);
     try {
       sessionRule.session().execute(LARGE_QUERY);

integration-tests/src/test/java/com/datastax/oss/driver/api/core/cql/AsyncResultSetIT.java

@@ -85,7 +85,7 @@ public static void setupSchema() {
   public void should_only_iterate_over_rows_in_current_page() throws Exception {
     // very basic test that just ensures that iterating over an AsyncResultSet only visits the first
     // page.
-    CompletionStage<AsyncResultSet> result =
         sessionRule
             .session()
             .executeAsync(