fix(button)!: type is submit by default

Also fixes the button not being the correct `submitter` for submit events.

BREAKING CHANGE: Buttons submit forms by default, like `<button>`. Add `type="button"` to not submit forms.

PiperOrigin-RevId: 553248284

button/filled-button_test.ts

@@ -31,6 +31,11 @@ describe('<md-filled-button>', () => {
       return {harness: new ButtonHarness(element), form};
     }
 
+    it('button is submit type by default', async () => {
+      const {harness} = await setupTest();
+      expect(harness.element.type).toBe('submit');
+    });
+
     it('button with type submit can submit a form', async () => {
       const {harness, form} = await setupTest();
       harness.element.type = 'submit';
@@ -69,5 +74,23 @@ describe('<md-filled-button>', () => {
 
       expect(form.requestSubmit).not.toHaveBeenCalled();
     });
+
+    it('should set the button as the SubmitEvent submitter', async () => {
+      const {harness, form} = await setupTest();
+      const submitListener =
+          jasmine.createSpy('submitListener').and.callFake((event: Event) => {
+            event.preventDefault();
+          });
+
+      form.addEventListener('submit', submitListener);
+
+      await harness.clickWithMouse();
+
+      expect(submitListener).toHaveBeenCalled();
+      const event = submitListener.calls.argsFor(0)[0] as SubmitEvent;
+      expect(event.submitter)
+          .withContext('event.submitter')
+          .toBe(harness.element);
+    });
   });
 });

button/internal/button.ts

@@ -63,11 +63,15 @@ export abstract class Button extends LitElement {
   @property({type: Boolean, attribute: 'has-icon'}) hasIcon = false;
 
   /**
-   * Specifies the type of button, used for controlling forms. When type
-   * is `submit`, the containing form is submitted; when it is `reset` the
-   * form is reset.
+   * A string indicating the behavior of the button.
+   *
+   * - submit: The button submits the form. This is the default value if the
+   * attribute is not specified, or if it is dynamically changed to an empty or
+   * invalid value.
+   * - reset: The button resets the form.
+   * - button: The button does nothing.
    */
-  @property() type: ''|'submit'|'reset' = '';
+  @property() type: 'button'|'submit'|'reset' = 'submit';
 
   @query('.button') private readonly buttonElement!: HTMLElement|null;
 
@@ -185,25 +189,35 @@ export abstract class Button extends LitElement {
     }
     // based on type, trigger form action.
     const {type, internals: {form}} = this;
-    if (!form) {
-      return;
-    }
-    const isSubmit = type === 'submit', isReset = type === 'reset';
-    if (!(isSubmit || isReset)) {
+    if (!form || type === 'button') {
       return;
     }
-    event.stopPropagation();
+
     this.isRedispatchingEvent = true;
     const prevented = !redispatchEvent(this, event);
     this.isRedispatchingEvent = false;
     if (prevented) {
       return;
     }
-    if (isSubmit) {
-      form.requestSubmit();
-    } else if (isReset) {
+
+    if (type === 'reset') {
       form.reset();
+      return;
     }
+
+    // form.requestSubmit(submitter) does not work with form associated custom
+    // elements. This patches the dispatched submit event to add the correct
+    // `submitter`.
+    // See https://github.com/WICG/webcomponents/issues/814
+    form.addEventListener('submit', submitEvent => {
+      Object.defineProperty(submitEvent, 'submitter', {
+        configurable: true,
+        enumerable: true,
+        get: () => this,
+      });
+    }, {capture: true, once: true});
+
+    form.requestSubmit();
   }
 
   private handleSlotChange() {