Expose textAlign on TextFormField (#13414)

* Expose textAlign on TextFormField

Fixes #11404

* Added name to AUTHORS

* Added a test for TextFormWidget's textAlign

AUTHORS

@@ -18,3 +18,4 @@ Mike Hoolehan <mike@hoolehan.com>
 German Saprykin <saprykin.h@gmail.com>
 Stefano Rodriguez <hlsroddy@gmail.com>
 Yusuke Konishi <yahpeycoy0403@gmail.com>
+Fredrik Simón <fredrik@fsimon.net>

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

@@ -48,6 +48,7 @@ class TextFormField extends FormField<String> {
     InputDecoration decoration: const InputDecoration(),
     TextInputType keyboardType: TextInputType.text,
     TextStyle style,
+    TextAlign textAlign: TextAlign.start,
     bool autofocus: false,
     bool obscureText: false,
     bool autocorrect: true,
@@ -57,6 +58,7 @@ class TextFormField extends FormField<String> {
     List<TextInputFormatter> inputFormatters,
   }) : assert(initialValue != null),
        assert(keyboardType != null),
+       assert(textAlign != null),
        assert(autofocus != null),
        assert(obscureText != null),
        assert(autocorrect != null),
@@ -74,6 +76,7 @@ class TextFormField extends FormField<String> {
         decoration: decoration.copyWith(errorText: field.errorText),
         keyboardType: keyboardType,
         style: style,
+        textAlign: textAlign,
         autofocus: autofocus,
         obscureText: obscureText,
         autocorrect: autocorrect,

packages/flutter/test/material/text_form_field_test.dart

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Passes textAlign to underlying TextField', (WidgetTester tester) async {
+    const TextAlign alignment = TextAlign.center;
+
+    await tester.pumpWidget(
+      new MaterialApp(
+        home: new Material(
+          child: new Center(
+            child: new TextFormField(
+              textAlign: alignment,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final Finder textFieldFinder = find.byType(TextField);
+    expect(textFieldFinder, findsOneWidget);
+
+    final TextField textFieldWidget = tester.widget(textFieldFinder);
+    expect(textFieldWidget.textAlign, alignment);
+  });
+}