Allow setting placeholder for st.multiselect

e2e/scripts/st_multiselect.py

@@ -26,7 +26,7 @@ def set_multiselect_9_to_have_bad_state():
 
 options = ("male", "female")
 
-i1 = st.multiselect("multiselect 1", options)
+i1 = st.multiselect("multiselect 1", options, placeholder="Please select")
 st.text(f"value 1: {i1}")
 
 i2 = st.multiselect("multiselect 2", options, format_func=lambda x: x.capitalize())

e2e/specs/st_multiselect.spec.js

@@ -79,7 +79,7 @@ describe("st.multiselect", () => {
       it("should show the correct placeholder", () => {
         cy.get(".stMultiSelect")
           .first()
-          .should("have.text", "multiselect 1Choose an optionopen");
+          .should("have.text", "multiselect 1Please selectopen");
       });
     });
 

frontend/src/lib/components/widgets/Multiselect/Multiselect.test.tsx

@@ -32,6 +32,7 @@ const getProps = (elementProps: Partial<MultiSelectProto> = {}): Props => ({
     label: "Label",
     default: [0],
     options: ["a", "b", "c"],
+    placeholder: "Please select",
     ...elementProps,
   }),
   width: 0,
@@ -114,9 +115,7 @@ describe("Multiselect widget", () => {
     it("renders when it's not empty", () => {
       const props = getProps()
       const wrapper = mount(<Multiselect {...props} />)
-      expect(wrapper.find(UISelect).prop("placeholder")).toBe(
-        "Choose an option"
-      )
+      expect(wrapper.find(UISelect).prop("placeholder")).toBe("Please select")
     })
 
     it("renders with empty options", () => {

frontend/src/lib/components/widgets/Multiselect/Multiselect.tsx

@@ -215,7 +215,7 @@ class Multiselect extends React.PureComponent<Props, State> {
     const { options } = element
     const disabled = options.length === 0 ? true : this.props.disabled
     const placeholder =
-      options.length === 0 ? "No options to select." : "Choose an option"
+      options.length === 0 ? "No options to select." : element.placeholder
     const selectOptions: MultiselectOption[] = options.map(
       (option: string, idx: number) => {
         return {

lib/streamlit/elements/multiselect.py

@@ -155,9 +155,10 @@ def multiselect(
         args: Optional[WidgetArgs] = None,
         kwargs: Optional[WidgetKwargs] = None,
         *,  # keyword-only arguments:
+        max_selections: Optional[int] = None,
+        placeholder: str = "Choose an option",
         disabled: bool = False,
         label_visibility: LabelVisibility = "visible",
-        max_selections: Optional[int] = None,
     ) -> List[T]:
         r"""Display a multiselect widget.
         The multiselect widget starts as empty.
@@ -213,6 +214,11 @@ def multiselect(
             An optional tuple of args to pass to the callback.
         kwargs : dict
             An optional dict of kwargs to pass to the callback.
+        max_selections : int
+            The max selections that can be selected at a time.
+            This argument can only be supplied by keyword.
+        placeholder : str
+            An optional string to display when option is not selected.
         disabled : bool
             An optional boolean, which disables the multiselect widget if set
             to True. The default is False. This argument can only be supplied
@@ -222,9 +228,6 @@ def multiselect(
             is still empty space for it above the widget (equivalent to label="").
             If "collapsed", both the label and the space are removed. Default is
             "visible". This argument can only be supplied by keyword.
-        max_selections : int
-            The max selections that can be selected at a time.
-            This argument can only be supplied by keyword.
 
         Returns
         -------
@@ -258,10 +261,11 @@ def multiselect(
             on_change=on_change,
             args=args,
             kwargs=kwargs,
+            max_selections=max_selections,
+            placeholder=placeholder,
             disabled=disabled,
             label_visibility=label_visibility,
             ctx=ctx,
-            max_selections=max_selections,
         )
 
     def _multiselect(
@@ -276,10 +280,11 @@ def _multiselect(
         args: Optional[WidgetArgs] = None,
         kwargs: Optional[WidgetKwargs] = None,
         *,  # keyword-only arguments:
+        max_selections: Optional[int] = None,
+        placeholder: str = "Choose an option",
         disabled: bool = False,
         label_visibility: LabelVisibility = "visible",
         ctx: Optional[ScriptRunContext] = None,
-        max_selections: Optional[int] = None,
     ) -> List[T]:
         key = to_key(key)
         check_callback_rules(self.dg, on_change)
@@ -296,6 +301,7 @@ def _multiselect(
         multiselect_proto.options[:] = [str(format_func(option)) for option in opt]
         multiselect_proto.form_id = current_form_id(self.dg)
         multiselect_proto.max_selections = max_selections or 0
+        multiselect_proto.placeholder = placeholder
         if help is not None:
             multiselect_proto.help = dedent(help)
 

lib/tests/streamlit/elements/multiselect_test.py

@@ -138,6 +138,7 @@ def test_defaults(self, defaults, expected):
         self.assertEqual(c.label, "the label")
         self.assertListEqual(c.default[:], expected)
         self.assertEqual(c.options, ["Coffee", "Tea", "Water"])
+        self.assertEqual(c.placeholder, "Choose an option")
 
     @parameterized.expand(
         [
@@ -365,3 +366,12 @@ def test_get_over_max_options_message(
             _get_over_max_options_message(current_selections, max_selections),
             expected_msg,
         )
+
+    def test_placeholder(self):
+        """Test that it can be called with placeholder params."""
+        st.multiselect(
+            "the label", ["Coffee", "Tea", "Water"], placeholder="Select your beverage"
+        )
+
+        c = self.get_delta_from_queue().new_element.multiselect
+        self.assertEqual(c.placeholder, "Select your beverage")

proto/streamlit/proto/MultiSelect.proto

@@ -27,7 +27,8 @@ message MultiSelect {
   string form_id = 6;
   repeated int32 value = 7;
   bool set_value = 8;
-  bool disabled = 9;
-  LabelVisibilityMessage label_visibility = 10;
-  int32 max_selections = 11;
+  int32 max_selections = 9;
+  string placeholder = 10;
+  bool disabled = 11;
+  LabelVisibilityMessage label_visibility = 12;
 }