flask-wtf表单中PasswordField无法回传显示密码问题解决方法

flask-wtf中的PasswordField默认是无法将后端回传的密码数据显示出来的，可以通过修改PasswordInput来实现，在PasswordInput源码中有一个参数来决定能不能将密码显示
PasswordField源码

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源码

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)

从PasswordInput的代码中可以知道hide_value决定了能不能显示密码，只需要将hide_value的值改为False就可以，可以改源码，但是不现实，下面通过继承来解决：

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()

亲测可用。