[LiveComponent] consider data-value attribute

src/LiveComponent/README.md

@@ -370,6 +370,27 @@ code works identically to the previous example:
 If an element has _both_ `data-model` and `name` attributes, the
 `data-model` attribute takes precedence.
 
+### Using data-value="" for non input elements
+
+If you want to set the value of a model with an element that is not an input element and does not have a `value` attribute you can use `data-value`
+
+```twig
+<div {{ init_live_component(this)>
+
+    <a
+        data-action="live#update"
+        data-model="min"
+        data-value="10">
+        Set min to 10
+    </a>
+
+    // ...
+</div>
+```
+
+If an element has _both_ `data-value` and `value` attributes, the
+`data-value` attribute takes precedence.
+
 ## Loading States
 
 Often, you'll want to show (or hide) an element while a component is

src/LiveComponent/assets/dist/live_controller.js

@@ -1057,11 +1057,11 @@ class default_1 extends Controller {
         window.removeEventListener('beforeunload', this.markAsWindowUnloaded);
     }
     update(event) {
-        const value = event.target.value;
+        const value = this._getValueFromElement(event.target);
         this._updateModelFromElement(event.target, value, true);
     }
     updateDefer(event) {
-        const value = event.target.value;
+        const value = this._getValueFromElement(event.target);
         this._updateModelFromElement(event.target, value, false);
     }
     action(event) {
@@ -1111,6 +1111,17 @@ class default_1 extends Controller {
     $render() {
         this._makeRequest(null);
     }
+    _getValueFromElement(element) {
+        const value = element.dataset.value || element.value;
+        if (!value) {
+            const clonedElement = (element.cloneNode());
+            if (!(clonedElement instanceof HTMLElement)) {
+                throw new Error('cloneNode() produced incorrect type');
+            }
+            throw new Error(`The update() method could not be called for "${clonedElement.outerHTML}": the element must either have a "data-value" or "value" attribute set.`);
+        }
+        return value;
+    }
     _updateModelFromElement(element, value, shouldRender) {
         const model = element.dataset.model || element.getAttribute('name');
         if (!model) {

src/LiveComponent/assets/src/live_controller.ts

@@ -110,13 +110,13 @@ export default class extends Controller {
      * Called to update one piece of the model
      */
     update(event: any) {
-        const value = event.target.value;
+        const value = this._getValueFromElement(event.target);
 
         this._updateModelFromElement(event.target, value, true);
     }
 
     updateDefer(event: any) {
-        const value = event.target.value;
+        const value = this._getValueFromElement(event.target);
 
         this._updateModelFromElement(event.target, value, false);
     }
@@ -195,6 +195,22 @@ export default class extends Controller {
         this._makeRequest(null);
     }
 
+    _getValueFromElement(element: HTMLElement){
+        const value = element.dataset.value || element.value;
+
+        if (!value) {
+            const clonedElement = (element.cloneNode());
+            // helps typescript know this is an HTMLElement
+            if (!(clonedElement instanceof HTMLElement)) {
+                throw new Error('cloneNode() produced incorrect type');
+            }
+
+            throw new Error(`The update() method could not be called for "${clonedElement.outerHTML}": the element must either have a "data-value" or "value" attribute set.`);
+        }
+
+        return value;
+    }
+
     _updateModelFromElement(element: HTMLElement, value: string, shouldRender: boolean) {
         const model = element.dataset.model || element.getAttribute('name');
 

src/LiveComponent/assets/test/controller/model.test.ts

@@ -11,7 +11,7 @@
 
 import { clearDOM } from '@symfony/stimulus-testing';
 import { initLiveComponent, mockRerender, startStimulus } from '../tools';
-import { getByLabelText, waitFor } from '@testing-library/dom';
+import {getByLabelText, getByText, waitFor} from '@testing-library/dom';
 import userEvent from '@testing-library/user-event';
 import fetchMock from 'fetch-mock-jest';
 
@@ -28,6 +28,7 @@ describe('LiveController data-model Tests', () => {
                 value="${data.name}"
             >
             </label>
+            <a data-action="live#update" data-model="name" data-value="Jan">Change name to Jan</a>
         </div>
     `;
 
@@ -61,6 +62,25 @@ describe('LiveController data-model Tests', () => {
         expect(document.activeElement.dataset.model).toEqual('name');
     });
 
+    it('renders correctly with data-value and live#update', async () => {
+        const data = { name: 'Ryan' };
+        const { element, controller } = await startStimulus(template(data));
+
+        fetchMock.getOnce('end:?name=Jan', {
+            html: template({ name: 'Jan' }),
+            data: { name: 'Jan' }
+        });
+
+        userEvent.click(getByText(element, 'Change name to Jan'));
+
+        await waitFor(() => expect(getByLabelText(element, 'Name:')).toHaveValue('Jan'));
+        expect(controller.dataValue).toEqual({name: 'Jan'});
+
+        // assert all calls were done the correct number of times
+        fetchMock.done();
+    });
+
+
     it('correctly only uses the most recent render call results', async () => {
         const data = { name: 'Ryan' };
         const { element, controller } = await startStimulus(template(data));
@@ -148,6 +168,27 @@ describe('LiveController data-model Tests', () => {
         fetchMock.done();
     });
 
+    it('uses data-value when both value and data-value is present', async () => {
+        const data = { name: 'Ryan' };
+        const { element, controller } = await startStimulus(template(data));
+
+        // give element data-model="name" and name="first_name"
+        const inputElement = getByLabelText(element, 'Name:');
+        inputElement.dataset.value = 'first_name';
+
+        // ?name should be what's sent to the server
+        mockRerender({name: 'first_name'}, template, (data) => {
+            data.name = 'first_name';
+        })
+
+        await userEvent.type(inputElement, ' WEAVER');
+
+        await waitFor(() => expect(inputElement).toHaveValue('first_name'));
+        expect(controller.dataValue).toEqual({name: 'first_name'});
+
+        fetchMock.done();
+    });
+
     it('standardizes user[firstName] style models into post.name', async () => {
         const deeperModelTemplate = (data) => `
             <div