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I found that IntegerField does not validate when empty. To reproduce, copy the following block:
from flask import Flask, render_template_string
from flask_wtf import FlaskForm
from wtforms import IntegerField
app = Flask(__name__)
app.config['WTF_CSRF_ENABLED'] = False
class DemoForm(FlaskForm):
demofield = IntegerField('demofield')
@app.route('/', methods=("GET","POST"))
def index():
form = DemoForm()
if form.validate_on_submit():
return ("The form validated!")
return render_template_string("<!DOCTYPE HTML> This is my form! <form method=\"post\">{% for field in form %}{{field}}{% endfor %}<input type=\"submit\">", form=form)
app.run(debug=True)
and save it in its own directory as app.py. Then open a terminal, cd to the directory, and run the following:
virtualenv flask
source flask/bin/activate
pip install flask flask-wtf
export FLASK_APP=app.py
python3 app.py
Connect to localhost:5000 in a web browser. Typing an integer into the form field and submitting will display "The form validated!" Typing something that is not an integer into the field, or leaving the field blank, and submitting just reloads the page. This does make some sense, since "" cannot be coerced into an integer.
I want to let my IntegerField be empty. I think the solution is to subclass IntegerField and override pre_validate() or post_validate(). I have:
class OptionalIntegerField(IntegerField):
def post_validate(self, form, validation_stopped):
print("post_validate is being called")
if (self.data in (None, "")):
return True
My question is:
return True inside them?
510
The Optional validator allows empty entries on form fields.
>>> from webob.multidict import MultiDict
>>> class F(Form):
... foo = IntegerField(validators=[validators.Optional()])
>>> f = F(formdata=MultiDict(foo=1))
>>> f.validate()
True
>>> f = F(formdata=MultiDict(foo=''))
>>> f.validate()
True
>>> f = F(formdata=MultiDict(foo='a'))
>>> f.validate()
False
From the docs:
class wtforms.validators.Optional(strip_whitespace=True)
Allows empty input and stops the validation chain from continuing.
If input is empty, also removes prior errors (such as processing errors) from the field.
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