validate_on_submit (flask-wtf) not working - flask

Question

I'm working on a sign-up page. The problem is that even if I submit new_user data, it won't store the new_user data in database and returns users/signup.html instead.
I believe validate_on_submit somehow causes the problem here. How can I store new_user data correctly?
users_bp.py
from flask import Blueprint
from flask_login import login_user, logout_user, current_user
from flask import redirect, render_template, request, flash
from flask import url_for
from flask_login import LoginManager
from werkzeug.security import generate_password_hash, check_password_hash
#login_manager.user_loader
def user_loader(user_id):
return User.query.get(int(user_id))
#user.route('/signup', methods=['GET', 'POST'])
def signup():
form = SignupForm()
if form.validate_on_submit():
nickname = form.nickname.data
email = form.email.data
password = form.password.data
user = User.query.filter_by(email=email).first()
if user:
return render_template('users/login.html')
new_user = User(email=email, nickname=nickname,
password=generate_password_hash('password', method='sha256'))
db.session.add(new_user)
db.session.commit()
return render_template('home.html')
return render_template('users/signup.html', form=form)
user_form.py
from flask.app import Flask
from flask.templating import render_template
from wtforms import TextAreaField, StringField, Form, SelectField, SubmitField, PasswordField, DateField
from flask_wtf import FlaskForm
from wtforms.validators import DataRequired
from werkzeug.utils import redirect
class SignupForm(FlaskForm):
nickname = StringField('nickname')
email = StringField('email', validators=[DataRequired(), Email()])
password = PasswordField('password', validators=[DataRequired()])
recaption = RecaptchaField()
send = SubmitField('submit')
users/signup.html
{% block content %}
<div class="info-container">
<div class="column is-4 is-offset-4">
<h2 class="title">新規登録</h2>
<div class="sign-description login-description">アカウントをお持ちの方はこちらからログインしてください
</div>
</div>
</div>
<form action="" id="SignupForm" method="POST">
{{ form.hidden_tag() }}
<div class="form-group m-5">
{{ form.nickname.label() }}
{{ form.nickname(class='form-control') }}
{% if form.nickname.errors %}
<ul class="errors">
{% for error in form.nickname.errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
</div>
<div class="form-group m-5">
{{ form.email.label() }}
{{ form.email(class='form-control') }}
{% if form.email.errors %}
<ul class="errors">
{% for error in form.email.errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
</div>
<div class="form-group m-5">
{{ form.password.label() }}
{{ form.password(class='form-control') }}
{% if form.password.errors %}
<ul class="errors">
{% for error in form.password.errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
</div>
{{ form.send(class='btn btn-outline-dark mb-5 form-control') }}
</form>
{% endblock %}

Answer 1

One guess: the problem could be the missing captcha, which is defined in your form model. If any of the requirements in your form class is not satisfied then validate_on_submit should fail. But you are not handling that condition.
Use form.errors to spit out validation errors if any...
I guess you are using Bootstrap, personally I use something like this in my form templates:
{% if form.is_submitted() and form.errors|count > 0 %}
<div class="alert alert-danger alert-dismissible fade show" role="alert">
{{ form.errors|count }} error(s):
<ul>
{% for field_name, field_errors in form.errors|dictsort if field_errors %}
{% for error in field_errors %}
<li>{{ form[field_name].label }}: {{ error }}</li>
{% endfor %}
{% endfor %}
<button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
</div>
{% endif %}
This will show a red box listing the form errors (if any).
If the form does not validate you need to tell the user somehow.