Sample code for Flutter issue https://github.com/flutter/flutter/issues/48099

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => MaterialApp(
        debugShowCheckedModeBanner: false,
        home: MyHomePage(),
      );
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Padding(
          padding: EdgeInsets.all(20),
          child: TextFormField(
            initialValue: "Abcdefgh1234",
            enableInteractiveSelection: false,
            readOnly: false,
          ),
        ),
      ),
    );
  }
}

This is an additional sample for Flutter flutter/flutter#48099 issue so I can provide it as link and with a DartPad to run.