[Explore] Fix annotation layer select box formatting (apache#8734)

superset/assets/src/explore/components/controls/AnnotationLayer.jsx

@@ -41,6 +41,7 @@ import ANNOTATION_TYPES, {
 import PopoverSection from '../../../components/PopoverSection';
 import ControlHeader from '../ControlHeader';
 import { nonEmpty } from '../../validators';
+import './AnnotationLayer.less';
 
 const AUTOMATIC_COLOR = '';
 
@@ -331,6 +332,14 @@ export default class AnnotationLayer extends React.PureComponent {
     this.props.close();
   }
 
+  renderOption(option) {
+    return (
+      <span className="optionWrapper" title={option.label}>
+        {option.label}
+      </span>
+    );
+  }
+
   renderValueConfiguration() {
     const {
       annotationType,
@@ -373,6 +382,7 @@ export default class AnnotationLayer extends React.PureComponent {
           value={value}
           onChange={this.handleValue}
           validationErrors={!value ? ['Mandatory'] : []}
+          optionRenderer={this.renderOption}
         />
       );
     }

superset/assets/src/explore/components/controls/AnnotationLayer.less

@@ -0,0 +1,24 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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
+ *
+ *   http://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.
+ */
+
+.optionWrapper {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}