为什么 Flask-Admin 在尝试编辑模型时会抛出此异常？

Question

AttributeError: 'StringField' object has no attribute 'wrap_formdata' 例外，它似乎只发生在我从 Flask-Admin 仪表板创建或编辑以下两个模型中的任何一个时：

class Experiment(db.Model):
    id = db.Column(db.Integer, primary_key=True)

    property_id = db.Column(db.Integer,
                            db.ForeignKey('property.id'),
                            index=True,
                            nullable=False)

    name = db.Column(db.String, nullable=False)

    start_date = db.Column(db.DateTime, nullable=True)
    end_date = db.Column(db.DateTime, nullable=True)
    status = db.Column(db.String, nullable=False, default='Draft')

    title = db.Column(db.String)
    meta = db.Column(db.String)
    seed_uri = db.Column(db.String)

    targets = db.Column(postgresql.JSON)
    variations_json = db.Column(postgresql.JSON)

    variations = db.relationship('ExperimentVariation',
                                  backref='experiment',
                                  cascade='save-update, merge, delete')

    def __repr__(self):
        repr_fmt = '<Experiment {id}, {property_id} {name}>'
        return repr_fmt.format(id=self.id,
                               property_id=self.property_id,
                               name=self.name)


class ExperimentVariation(db.Model):
    id = db.Column(db.Integer, primary_key=True)

    experiment_id = db.Column(db.Integer,
                              db.ForeignKey('experiment.id'),
                              index=True,
                              nullable=False)

    name = db.Column(db.String, nullable=False)

    title = db.Column(db.String)
    meta = db.Column(db.String)

    def __repr__(self):
        repr_fmt = '<ExperimentVariation {id}, {experiment_id} {name}>'
        return repr_fmt.format(id=self.id,
                               experiment_id=self.experiment_id,
                               name=self.name)

我想知道这些关系是否有些复杂。如果有帮助，我可以提供 Property 模型，但简而言之，该模型的大部分只是提供其他模型之间的关系，包括 Experiment 模型。

快速谷歌似乎没有发现类似的问题。我很可能忽略了一些明显的东西，或者可能没有完全理解关系 API。

为了清楚起见，我还在下面包含了完整的回溯：

ERROR [ranksci] Exception on /admin/experiment/edit/ [GET]
Traceback (most recent call last):
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask/app.py", line 1988, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask/app.py", line 1641, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask/app.py", line 1544, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask/app.py", line 1639, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask/app.py", line 1625, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask_admin/base.py", line 69, in inner
    return self._run_view(f, *args, **kwargs)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask_admin/base.py", line 368, in _run_view
    return fn(self, *args, **kwargs)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask_admin/model/base.py", line 1969, in edit_view
    form = self.edit_form(obj=model)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask_admin/model/base.py", line 1256, in edit_form
    return self._edit_form_class(get_form_data(), obj=obj)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/wtforms/form.py", line 212, in __call__
    return type.__call__(cls, *args, **kwargs)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/flask_admin/form/__init__.py", line 16, in __init__
    super(BaseForm, self).__init__(formdata=formdata, obj=obj, prefix=prefix, **kwargs)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/wtforms/form.py", line 278, in __init__
    self.process(formdata, obj, data=data, **kwargs)
  File "/Users/max/Documents/projects/ranksci-app/virtualenv/lib/python2.7/site-packages/wtforms/form.py", line 119, in process
    formdata = self.meta.wrap_formdata(self, formdata)
AttributeError: 'StringField' object has no attribute 'wrap_formdata'

Answer 1

我已经找出了这个问题的根本原因：Flask-Admin 构造了一个表单类，默认情况下，它从每个 SQLA 模型子类化了一个 WTForm 的 Form 类。这一切都很好，除非您的列之一与 WTForm 的构造函数采用的参数之一匹配，例如 meta。

构造上述类的逻辑是here。我不完全确定正确的解决方法是什么，但它似乎是 Flask-Admin 需要在技术上或社交上处理的情况。例如，提前知道 meta 不应用作列名会很方便，因为会发生此问题。

值得指出的是，WTForm 的 Form 构造函数也接受以下变量，因此也应该避免使用：formdata、obj、prefix 和 data。

此问题的技术解决方案可能是构造一组这些变量名，然后在上述 Flask-Admin 代码中创建模型表单时显式检查它们。然后可以生成某种警告，或者可以更改name 变量，使其以_ 或类似名称为前缀。这不是一个完美的解决方案，因为当然 WTForms 将来可能会更改其 API。