Fix bug where Enter doesn't add new line in multi-line fields (#13630)

lib/web_ui/lib/src/engine/text_editing/input_type.dart

@@ -59,6 +59,9 @@ abstract class EngineInputType {
   /// <https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/inputmode>.
   String get inputmodeAttribute;
 
+  /// Whether this input type allows the "Enter" key to submit the input action.
+  bool get submitActionOnEnter => true;
+
   /// Create the appropriate DOM element for this input type.
   html.HtmlElement createDomElement() => html.InputElement();
 
@@ -124,6 +127,9 @@ class MultilineInputType extends EngineInputType {
   @override
   final String inputmodeAttribute = null;
 
+  @override
+  bool get submitActionOnEnter => false;
+
   @override
   html.HtmlElement createDomElement() => html.TextAreaElement();
 }

lib/web_ui/lib/src/engine/text_editing/text_editing.dart

@@ -437,7 +437,8 @@ class TextEditingElement {
   }
 
   void _maybeSendAction(html.KeyboardEvent event) {
-    if (event.keyCode == _kReturnKeyCode) {
+    if (_inputConfiguration.inputType.submitActionOnEnter &&
+        event.keyCode == _kReturnKeyCode) {
       event.preventDefault();
       _onAction(_inputConfiguration.inputAction);
     }

lib/web_ui/test/text_editing_test.dart

@@ -13,6 +13,9 @@ import 'package:test/test.dart';
 
 import 'matchers.dart';
 
+/// The `keyCode` of the "Enter" key.
+const int _kReturnKeyCode = 13;
+
 const MethodCodec codec = JSONMethodCodec();
 
 TextEditingElement editingElement;
@@ -250,10 +253,41 @@ void main() {
       // No input action so far.
       expect(lastInputAction, isNull);
 
-      dispatchKeyboardEvent(editingElement.domElement, 'keydown', keyCode: 13);
+      dispatchKeyboardEvent(
+        editingElement.domElement,
+        'keydown',
+        keyCode: _kReturnKeyCode,
+      );
       expect(lastInputAction, 'TextInputAction.done');
     });
 
+    test('Does not trigger input action in multi-line mode', () {
+      final InputConfiguration config = InputConfiguration(
+        inputType: EngineInputType.multiline,
+        obscureText: false,
+        inputAction: 'TextInputAction.done',
+      );
+      editingElement.enable(
+        config,
+        onChange: trackEditingState,
+        onAction: trackInputAction,
+      );
+
+      // No input action so far.
+      expect(lastInputAction, isNull);
+
+      final KeyboardEvent event = dispatchKeyboardEvent(
+        editingElement.domElement,
+        'keydown',
+        keyCode: _kReturnKeyCode,
+      );
+
+      // Still no input action.
+      expect(lastInputAction, isNull);
+      // And default behavior of keyboard event shouldn't have been prevented.
+      expect(event.defaultPrevented, isFalse);
+    });
+
     group('[persistent mode]', () {
       test('Does not accept dom elements of a wrong type', () {
         // A regular <span> shouldn't be accepted.
@@ -883,7 +917,7 @@ void main() {
       dispatchKeyboardEvent(
         textEditing.editingElement.domElement,
         'keydown',
-        keyCode: 13,
+        keyCode: _kReturnKeyCode,
       );
 
       expect(spy.messages, hasLength(1));
@@ -894,6 +928,24 @@ void main() {
         <dynamic>[clientId, 'TextInputAction.next'],
       );
     });
+
+    test('does not send input action in multi-line mode', () {
+      showKeyboard(
+        inputType: 'multiline',
+        inputAction: 'TextInputAction.next',
+      );
+
+      final KeyboardEvent event = dispatchKeyboardEvent(
+        textEditing.editingElement.domElement,
+        'keydown',
+        keyCode: _kReturnKeyCode,
+      );
+
+      // No input action and no platform message have been sent.
+      expect(spy.messages, isEmpty);
+      // And default behavior of keyboard event shouldn't have been prevented.
+      expect(event.defaultPrevented, isFalse);
+    });
   });
 
   group('EditingState', () {