flask-wtf表單中PasswordField無法回傳顯示密碼問題解決方法

flask-wtf中的PasswordField默認是無法將後端回傳的密碼數據顯示出來的，可以通過修改PasswordInput來實現，在PasswordInput源碼中有一個參數來決定能不能將密碼顯示
PasswordField源碼

class PasswordField(StringField):
    """
    A StringField, except renders an ``<input type="password">``.

    Also, whatever value is accepted by this field is not rendered back
    to the browser like normal fields.
    """
    widget = widgets.PasswordInput()

PasswordInput源碼

class PasswordInput(Input):
    """
    Render a password input.

    For security purposes, this field will not reproduce the value on a form
    submit by default. To have the value filled in, set `hide_value` to
    `False`.
    """
    input_type = 'password'

    def __init__(self, hide_value=True):
        self.hide_value = hide_value

    def __call__(self, field, **kwargs):
        if self.hide_value:
            kwargs['value'] = ''
        return super(PasswordInput, self).__call__(field, **kwargs)

從PasswordInput的代碼中可以知道hide_value決定了能不能顯示密碼，只需要將hide_value的值改爲False就可以，可以改源碼，但是不現實，下面通過繼承來解決：

from wtforms.widgets.core import PasswordInput
from wtforms import PasswordField
from flask_wtf import FlaskForm

class MyPasswordField(PasswordField):
    widget = PasswordInput(hide_value=False)

使用方法：
class UserForm(FlaskForm):
    password = MyPasswordField()

親測可用。