Add search_value property to Dropdown

src/components/Dropdown.react.js

@@ -100,6 +100,7 @@ export default class Dropdown extends Component {
                             setProps({value});
                         }
                     }}
+                    onInputChange={search_value => setProps({search_value})}
                     {...omit(['setProps', 'value'], this.props)}
                 />
             </div>
@@ -195,6 +196,11 @@ Dropdown.propTypes = {
      */
     searchable: PropTypes.bool,
 
+    /**
+     * The value typed in the DropDown for searching.
+     */
+    search_value: PropTypes.string,
+
     /**
      * Dash-assigned callback that gets fired when the input changes
      */

tests/integration/dropdown/test_search_value.py

@@ -0,0 +1,36 @@
+from multiprocessing import Value
+import dash
+from dash.dependencies import Input, Output, State
+import dash.testing.wait as wait
+import dash_core_components as dcc
+import dash_html_components as html
+
+
+def test_ddsv001_search_value(dash_duo):
+    app = dash.Dash(__name__)
+    app.layout = html.Div(
+        [dcc.Dropdown(id="dropdown", search_value="something"), html.Div(id="output")]
+    )
+
+    call_count = Value("i", 0)
+
+    @app.callback(
+        Output("output", "children"), inputs=[Input("dropdown", "search_value")]
+    )
+    def update_output(search_value):
+        call_count.value += 1
+        return 'search_value="{}"'.format(search_value)
+
+    dash_duo.start_server(app)
+
+    # Get the inner input used for search value.
+    input_ = dash_duo.find_element("#dropdown input")
+
+    # callback gets called with initial input
+    wait.until(lambda: call_count.value == 1, timeout=1)
+
+    dash_duo.wait_for_text_to_equal("#output", 'search_value="something"')
+
+    input_.send_keys("x")
+    wait.until(lambda: call_count.value == 2, timeout=1)
+    dash_duo.wait_for_text_to_equal("#output", 'search_value="x"')

tests/unit/Dropdown.test.js

@@ -25,6 +25,7 @@ describe('Props can be set properly', () => {
         multi: false,
         placeholder: 'pick something',
         searchable: true,
+        search_value: "hello",
         style: {backgroundColor: 'hotpink'},
         loading_state: {
             is_loading: false,