Always honor explicitly set keyboardType and inputAction for TextField (#20547)

With this change you can now create "wrapping" text fields that do not show the new line button:

```dart
new TextField(
  maxLines: null,
  keyboardType: TextInputType.text,
);
```

packages/flutter/lib/src/material/text_field.dart

@@ -71,9 +71,7 @@ class TextField extends StatefulWidget {
   ///
   /// The [maxLines] property can be set to null to remove the restriction on
   /// the number of lines. By default, it is one, meaning this is a single-line
-  /// text field. [maxLines] must not be zero. If [maxLines] is not one, then
-  /// [keyboardType] is ignored, and the [TextInputType.multiline] keyboard
-  /// type is used.
+  /// text field. [maxLines] must not be zero.
   ///
   /// The [maxLength] property is set to null by default, which means the
   /// number of characters allowed in the text field is not restricted. If
@@ -89,8 +87,8 @@ class TextField extends StatefulWidget {
   /// characters may be entered, and the error counter and divider will
   /// switch to the [decoration.errorStyle] when the limit is exceeded.
   ///
-  /// The [keyboardType], [textAlign], [autofocus], [obscureText], and
-  /// [autocorrect] arguments must not be null.
+  /// The [textAlign], [autofocus], [obscureText], and [autocorrect] arguments
+  /// must not be null.
   ///
   /// See also:
   ///
@@ -101,8 +99,8 @@ class TextField extends StatefulWidget {
     this.controller,
     this.focusNode,
     this.decoration = const InputDecoration(),
-    TextInputType keyboardType = TextInputType.text,
-    this.textInputAction = TextInputAction.done,
+    TextInputType keyboardType,
+    this.textInputAction,
     this.textCapitalization = TextCapitalization.none,
     this.style,
     this.textAlign = TextAlign.start,
@@ -122,9 +120,7 @@ class TextField extends StatefulWidget {
     this.cursorColor,
     this.keyboardAppearance,
     this.scrollPadding = const EdgeInsets.all(20.0),
-  }) : assert(keyboardType != null),
-       assert(textInputAction != null),
-       assert(textAlign != null),
+  }) : assert(textAlign != null),
        assert(autofocus != null),
        assert(obscureText != null),
        assert(autocorrect != null),
@@ -132,7 +128,7 @@ class TextField extends StatefulWidget {
        assert(scrollPadding != null),
        assert(maxLines == null || maxLines > 0),
        assert(maxLength == null || maxLength > 0),
-       keyboardType = maxLines == 1 ? keyboardType : TextInputType.multiline,
+       keyboardType = keyboardType ?? (maxLines == 1 ? TextInputType.text : TextInputType.multiline),
        super(key: key);
 
   /// Controls the text being edited.
@@ -156,14 +152,14 @@ class TextField extends StatefulWidget {
 
   /// The type of keyboard to use for editing the text.
   ///
-  /// Defaults to [TextInputType.text]. Must not be null. If
-  /// [maxLines] is not one, then [keyboardType] is ignored, and the
-  /// [TextInputType.multiline] keyboard type is used.
+  /// Defaults to [TextInputType.text] if [maxLines] is one and
+  /// [TextInputType.multiline] otherwise.
   final TextInputType keyboardType;
 
   /// The type of action button to use for the keyboard.
   ///
-  /// Defaults to [TextInputAction.done]. Must not be null.
+  /// Defaults to [TextInputAction.newline] if [keyboardType] is
+  /// [TextInputType.multiline] and [TextInputAction.done] otherwise.
   final TextInputAction textInputAction;
 
   /// Configures how the platform keyboard will select an uppercase or

packages/flutter/lib/src/material/text_form_field.dart

@@ -54,9 +54,9 @@ class TextFormField extends FormField<String> {
     String initialValue,
     FocusNode focusNode,
     InputDecoration decoration = const InputDecoration(),
-    TextInputType keyboardType = TextInputType.text,
+    TextInputType keyboardType,
     TextCapitalization textCapitalization = TextCapitalization.none,
-    TextInputAction textInputAction = TextInputAction.done,
+    TextInputAction textInputAction,
     TextStyle style,
     TextAlign textAlign = TextAlign.start,
     bool autofocus = false,
@@ -75,8 +75,6 @@ class TextFormField extends FormField<String> {
     Brightness keyboardAppearance,
     EdgeInsets scrollPadding = const EdgeInsets.all(20.0),
   }) : assert(initialValue == null || controller == null),
-       assert(keyboardType != null),
-       assert(textInputAction != null),
        assert(textAlign != null),
        assert(autofocus != null),
        assert(obscureText != null),

packages/flutter/lib/src/widgets/editable_text.dart

@@ -201,7 +201,7 @@ class EditableText extends StatefulWidget {
     this.selectionColor,
     this.selectionControls,
     TextInputType keyboardType,
-    this.textInputAction = TextInputAction.done,
+    this.textInputAction,
     this.textCapitalization = TextCapitalization.none,
     this.onChanged,
     this.onEditingComplete,
@@ -597,9 +597,10 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
               inputType: widget.keyboardType,
               obscureText: widget.obscureText,
               autocorrect: widget.autocorrect,
-              inputAction: widget.keyboardType == TextInputType.multiline
+              inputAction: widget.textInputAction ?? (widget.keyboardType == TextInputType.multiline
                   ? TextInputAction.newline
-                  : widget.textInputAction,
+                  : TextInputAction.done
+              ),
               textCapitalization: widget.textCapitalization,
           )
       )..setEditingState(localValue);
@@ -1036,4 +1037,4 @@ class _Editable extends LeafRenderObjectWidget {
       ..cursorWidth = cursorWidth
       ..cursorRadius = cursorRadius;
   }
-}
+}
\ No newline at end of file

packages/flutter/test/widgets/editable_text_test.dart

@@ -292,6 +292,65 @@ void main() {
         equals('TextInputAction.newline'));
   });
 
+  testWidgets('Multiline keyboard with newline action is requested when maxLines = null', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new FocusScope(
+          node: focusScopeNode,
+          autofocus: true,
+          child: new EditableText(
+            controller: controller,
+            focusNode: focusNode,
+            maxLines: null,
+            style: textStyle,
+            cursorColor: cursorColor,
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.byType(EditableText));
+    await tester.showKeyboard(find.byType(EditableText));
+    controller.text = 'test';
+    await tester.idle();
+    expect(tester.testTextInput.editingState['text'], equals('test'));
+    expect(tester.testTextInput.setClientArgs['inputType']['name'],
+        equals('TextInputType.multiline'));
+    expect(tester.testTextInput.setClientArgs['inputAction'],
+        equals('TextInputAction.newline'));
+  });
+
+  testWidgets('Text keyboard is requested when explicitly set and maxLines = null', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new FocusScope(
+          node: focusScopeNode,
+          autofocus: true,
+          child: new EditableText(
+            controller: controller,
+            focusNode: focusNode,
+            maxLines: null,
+            keyboardType: TextInputType.text,
+            style: textStyle,
+            cursorColor: cursorColor,
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.byType(EditableText));
+    await tester.showKeyboard(find.byType(EditableText));
+    controller.text = 'test';
+    await tester.idle();
+    expect(tester.testTextInput.editingState['text'], equals('test'));
+    expect(tester.testTextInput.setClientArgs['inputType']['name'],
+        equals('TextInputType.text'));
+    expect(tester.testTextInput.setClientArgs['inputAction'],
+        equals('TextInputAction.done'));
+  });
+
   testWidgets(
       'Correct keyboard is requested when set explicitly and maxLines > 1',
       (WidgetTester tester) async {