Fixes googleapis#3808. (googleapis#3873)

Now getTable of BigQueryImpl checks if the provided TableId has the
project set. If yes, the set projectId is used, otherwise the projectId
used when creating the BigQuery client will be used.

The additional test checks this behavior by calling getTableId with an
empty projectId.

Author: MMMarcy

google-cloud-clients/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryImpl.java

@@ -39,6 +39,7 @@
 import com.google.cloud.bigquery.spi.v2.BigQueryRpc;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
+import com.google.common.base.Strings;
 import com.google.common.base.Supplier;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
@@ -401,7 +402,12 @@ public Table getTable(final String datasetId, final String tableId, TableOption.
 
   @Override
   public Table getTable(TableId tableId, TableOption... options) {
-    final TableId completeTableId = tableId.setProjectId(getOptions().getProjectId());
+    // More context about why this: https://github.com/googleapis/google-cloud-java/issues/3808
+    final TableId completeTableId = tableId.setProjectId(
+        Strings.isNullOrEmpty(tableId.getProject())
+            ? getOptions().getProjectId()
+            : tableId.getProject()
+    );
     final Map<BigQueryRpc.Option, ?> optionsMap = optionMap(options);
     try {
       com.google.api.services.bigquery.model.Table answer =

google-cloud-clients/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/BigQueryImplTest.java

@@ -603,6 +603,20 @@ public void testGetTableFromTableIdWithProject() {
     assertEquals(new Table(bigquery, new TableInfo.BuilderImpl(tableInfo)), table);
   }
 
+  @Test
+  public void testGetTableFromTableIdWithoutProject() {
+    TableInfo tableInfo = TABLE_INFO.setProjectId(PROJECT);
+    TableId tableId = TableId.of("", TABLE_ID.getDataset(), TABLE_ID.getTable());
+    EasyMock.expect(bigqueryRpcMock.getTable(PROJECT, DATASET, TABLE, EMPTY_RPC_OPTIONS))
+        .andReturn(tableInfo.toPb());
+    EasyMock.replay(bigqueryRpcMock);
+    BigQueryOptions bigQueryOptions =
+        createBigQueryOptionsForProject(PROJECT, rpcFactoryMock);
+    bigquery = bigQueryOptions.getService();
+    Table table = bigquery.getTable(tableId);
+    assertEquals(new Table(bigquery, new TableInfo.BuilderImpl(tableInfo)), table);
+  }
+
   @Test
   public void testGetTableWithSelectedFields() {
     Capture<Map<BigQueryRpc.Option, Object>> capturedOptions = Capture.newInstance();