How to Remove Error Message in TextFormField in Flutter

Try the code bellow. No size adjustment for the error text, only the field border in red.

 TextFormField(
  decoration: InputDecoration(
    errorStyle: TextStyle(height: 0),
  ),
);

You can return an empty string which will still mark the borders red if not valid

 validator: (String value) {
      if (value.isEmpty) {
          return '';
     }
},

UPDATE

What I did to fix that was wrap the TextField with SizedBox and give a fixed height then want expand with error message

 SizedBox(
      height: SOME_FIXED_HEIGHT_INCLUDING_ERROR_MESSAGE'S_HEIGHT,
      child: TextField()

This works perfect for me. Looks pretty clean although you lose, of course, the error info coming from the validation.

TextFormField(
  decoration: const InputDecoration(
    errorBorder: OutlineInputBorder(
      borderSide: BorderSide(color: Colors.red),
    ),
    errorStyle: TextStyle(height: 0),
  ),
  validator: (_) => error ? '' : null,
  ),