Allow multiple selections on select box

demo/select_demo.py

@@ -3,12 +3,12 @@
 
 @me.stateclass
 class State:
-  selected_value: str = ""
+  selected_values: list[str]
 
 
 def on_selection_change(e: me.SelectSelectionChangeEvent):
   s = me.state(State)
-  s.selected_value = e.value
+  s.selected_values = e.values
 
 
 @me.page(
@@ -28,6 +28,7 @@ def app():
     ],
     on_selection_change=on_selection_change,
     style=me.Style(width=500),
+    multiple=True,
   )
   s = me.state(State)
-  me.text(text="Selected value: " + s.selected_value)
+  me.text(text="Selected values: " + ", ".join(s.selected_values))

mesop/components/select/e2e/__init__.py

@@ -1 +1,2 @@
 from . import select_app as select_app
+from . import select_app_multiple as select_app_multiple

mesop/components/select/e2e/select_app_multiple.py

@@ -0,0 +1,29 @@
+import mesop as me
+
+
+@me.stateclass
+class State:
+  selected_values: list[str]
+
+
+def on_selection_change(e: me.SelectSelectionChangeEvent):
+  s = me.state(State)
+  s.selected_values = e.values
+
+
+@me.page(path="/components/select/e2e/select_app_multiple")
+def app():
+  me.text(text="Select")
+  me.select(
+    label="Select",
+    options=[
+      me.SelectOption(label="label 1", value="value1"),
+      me.SelectOption(label="label 2", value="value2"),
+      me.SelectOption(label="label 3", value="value3"),
+    ],
+    on_selection_change=on_selection_change,
+    multiple=True,
+    style=me.Style(width=500),
+  )
+  s = me.state(State)
+  me.text(text="Selected values: " + ", ".join(s.selected_values))

mesop/components/select/e2e/select_test.ts

@@ -1,11 +1,25 @@
 import {test, expect} from '@playwright/test';
 
-test('test', async ({page}) => {
+test('single selection', async ({page}) => {
   await page.goto('/components/select/e2e/select_app');
+  await page.getByRole('combobox').click();
+  await page.getByRole('option', {name: 'label 2'}).click();
+  await expect(page.getByText('Selected value: value2')).toBeAttached();
+
+  await page.getByRole('combobox').click();
+  await page.getByRole('option', {name: 'label 3'}).click();
+  await expect(page.getByText('Selected value: value3')).toBeAttached();
+});
+
+test('multiple selection', async ({page}) => {
+  await page.goto('/components/select/e2e/select_app_multiple');
   await page.getByLabel('Select').click();
+
   await page.getByRole('option', {name: 'label 2'}).click();
+  await expect(page.getByText('Selected values: value2')).toBeAttached();
 
-  expect(
-    await page.getByText('Selected value: value2').textContent(),
-  ).toContain('Selected value: value2');
+  await page.getByRole('option', {name: 'label 1'}).click();
+  await expect(
+    page.getByText('Selected values: value1, value2'),
+  ).toBeAttached();
 });

mesop/components/select/select.ng.html

@@ -8,6 +8,7 @@
     [value]="config().getValue()"
     (openedChange)="onSelectOpenedChangeEvent($event)"
     (selectionChange)="onSelectSelectionChangeEvent($event)"
+    [multiple]="config().getMultiple()"
   >
     @for(option of config().getOptionsList(); track $index) {
     <mat-option [value]="option.getValue()">{{option.getLabel()}}</mat-option>

mesop/components/select/select.proto

@@ -3,9 +3,14 @@ syntax = "proto2";
 
 package mesop.components.select;
 
+message SelectChangeEvent {
+    repeated string values = 1;
+}
+
 message SelectType {
   optional bool disabled = 2;
   optional bool disable_ripple = 3;
+  optional bool multiple = 18;
   optional double tab_index = 4;
   optional string placeholder = 6;
   optional string value = 9;

mesop/components/select/select.py

@@ -35,23 +35,33 @@ class SelectOpenedChangeEvent(MesopEvent):
 
 @dataclass(kw_only=True)
 class SelectSelectionChangeEvent(MesopEvent):
-  """Event representing a change in the select component's value.
+  """Event representing a change in the select component's value(s).
 
   Attributes:
-      value: The new value of the select component after the change.
+      values: New values of the select component after the change.
       key (str): Key of the component that emitted this event.
   """
 
-  value: str
+  values: list[str]
 
+  @property
+  def value(self):
+    """Shortcut for returning a single value."""
+    if not self.values:
+      return ""
+    return self.values[0]
 
-register_event_mapper(
-  SelectSelectionChangeEvent,
-  lambda event, key: SelectSelectionChangeEvent(
+
+def map_select_change_event(event, key):
+  select_event = select_pb.SelectChangeEvent()
+  select_event.ParseFromString(event.bytes_value)
+  return SelectSelectionChangeEvent(
     key=key.key,
-    value=event.string_value,
-  ),
-)
+    values=list(select_event.values),
+  )
+
+
+register_event_mapper(SelectSelectionChangeEvent, map_select_change_event)
 
 
 @dataclass(kw_only=True)
@@ -82,6 +92,7 @@ def select(
   placeholder: str = "",
   value: str = "",
   style: Style | None = None,
+  multiple: bool = False,
 ):
   """Creates a Select component.
 
@@ -91,6 +102,7 @@ def select(
     on_opened_change: Event emitted when the select panel has been toggled.
     disabled: Whether the select is disabled.
     disable_ripple: Whether ripples in the select are disabled.
+    multiple: Whether multiple selections are allowed.
     tab_index: Tab index of the select.
     placeholder: Placeholder to be shown if no value has been selected.
     value: Value of the select control.
@@ -109,6 +121,7 @@ def select(
       label=label,
       disabled=disabled,
       disable_ripple=disable_ripple,
+      multiple=multiple,
       tab_index=tab_index,
       placeholder=placeholder,
       value=value,

mesop/components/select/select.ts

@@ -6,7 +6,10 @@ import {
   Type,
   Style,
 } from 'mesop/mesop/protos/ui_jspb_proto_pb/mesop/protos/ui_pb';
-import {SelectType} from 'mesop/mesop/components/select/select_jspb_proto_pb/mesop/components/select/select_pb';
+import {
+  SelectChangeEvent,
+  SelectType,
+} from 'mesop/mesop/components/select/select_jspb_proto_pb/mesop/components/select/select_pb';
 import {Channel} from '../../web/src/services/channel';
 import {formatStyle} from '../../web/src/utils/styles';
 
@@ -45,11 +48,18 @@ export class SelectComponent {
 
   onSelectSelectionChangeEvent(event: MatSelectChange): void {
     const userEvent = new UserEvent();
-
     userEvent.setHandlerId(
       this.config().getOnSelectSelectionChangeEventHandlerId()!,
     );
-    userEvent.setStringValue(event.value);
+    const changeEvent = new SelectChangeEvent();
+    if (typeof event.value === 'string') {
+      changeEvent.addValues(event.value);
+    } else {
+      for (const value of event.value) {
+        changeEvent.addValues(value);
+      }
+    }
+    userEvent.setBytesValue(changeEvent.serializeBinary());
     userEvent.setKey(this.key);
     this.channel.dispatch(userEvent);
   }