hidden tag missing argument

Question

I started using a macro for rendering fields, with errors, if I fail to validate the form, I get this error. If I use the correct credentials I get redirected to where I should and no errors are shown, if I fail to validate it tries to redirect to this same route but raises this error.

"C:\Users\ulman\PycharmProjects\database_website_optimised\source\database_website\applications\users\views.py", line 43, in post
    return render_template(self.template_name, title=self.title, form=self.form_class)
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\venv\lib\site-packages\flask\templating.py", line 140, in render_template
    ctx.app,
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\venv\lib\site-packages\flask\templating.py", line 120, in _render
    rv = template.render(context)
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\venv\lib\site-packages\jinja2\environment.py", line 1090, in render
    self.environment.handle_exception()
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\venv\lib\site-packages\jinja2\environment.py", line 832, in handle_exception
    reraise(*rewrite_traceback_stack(source=source))
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\venv\lib\site-packages\jinja2\_compat.py", line 28, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\source\database_website\applications\users\templates\users\login.html", line 3, in top-level template code
    {% from 'macros/_formhelpers.html' import render_field %}
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\source\database_website\templates\base.html", line 69, in top-level template code
    {% block content %}{% endblock %}
  File "C:\Users\ulman\PycharmProjects\database_website_optimised\source\database_website\applications\users\templates\users\login.html", line 9, in block "content"
    {{ form.hidden_tag() }}
TypeError: hidden_tag() missing 1 required positional argument: 'self'
127.0.0.1 - - [31/May/2020 11:29:52] "POST /login/ HTTP/1.1" 500 -

Here is my login.html file:

{% extends "base.html" %}

{% from 'macros/_formhelpers.html' import render_field %}

{% block content %}
 <div class="container">
        <div class="content-section">
            <form method="POST" action="">
                {{ form.hidden_tag() }}
                <fieldset class="form-group">
                    <legend class="border-bottom mb-4">Log In to your account</legend>
                    <div>
                        {{ render_field(form.email) }}
                    </div>
                    <div>
                        {{ render_field(form.password) }}
                    </div>
                    <div>{{ form.remember }} {{ form.remember.label }}</div>
                </fieldset>
                <div class="form-group">
                    {{ form.submit(class="btn btn-outline-info") }}
                </div>
            </form>
        </div>
        <div class="border-top pt-3">
            <small class="text-muted">
                Have not registered yet? <a href="{{ url_for('users.register') }}">Sign Up</a>
            </small>
        </div>
    </div>
{% endblock %}

And here is the macro _formhelpers.html file:

{% macro render_field(field) %}
    {{ field.label(class="form-control-label") }}

    {{ field(class="form-control form-control-lg") }}

    {% if field.errors %}
        <ul>
            {% for error in field.errors %}
                <li>{{ error }}</li>
            {% endfor %}
        </ul>
    {% endif %}
{% endmacro %}

Answer 1

Turns out it had nothing to do with my html file, instead when I was returning my login template again instead of

return render_template(self.template_name, title=self.title, form=self.form_class)

I needed to write this:

return render_template(self.template_name, title=self.title, form=self.form_class())

Got the solution idea from this post: Error: "TypeError: hidden_tag() missing 1 required positional argument: 'self' " in Flask, python