[Python] Debugging admin_base_template undefined using Flask Admin and Flask-security to...

Attempting to build a site using Python and Flask. I had made some basic pages before tackling an admin page for the uploading of content. Currently I am using Flask-Admin v 2.0.0a0 and Flask-Security 5.6.0. The problem I have is using the flask-admin views and attempting to integrate flask-security with the security_context_processor decorator. Admin page is returning and I cannot view the db items (since I am not logged in) but when I manually go to login page I receive a jinja error: jinja2.exceptions.UndefinedError: 'admin_base_template' is undefined

A majority of this is pulled from the flask-admin/flask-security working example from HERE but I am at a loss for what is going wrong

The route is admin/login/ which is set in config.py as such:

# Flask Security Config
# Flask-Security URLs, overridden because they don't put a / at the end
SECURITY_LOGIN_URL = "/login/"
SECURITY_POST_LOGIN_VIEW = "/admin/"
# Flask-Security config
SECURITY_URL_PREFIX = "/admin"


Below is the gist of the code and application structure:

Directory Structure
AppFolder
|
|- app.py
|- config.py
|- templates
|- base.html
|- index.html
|- admin <
| | - index.html
| | - user_edit.html
| | - post_edit.html
|- security <
| - login_user.html
| - _macros.html
| - _messages.html



app.py (relevant parts)

## App and App Config
app = Flask(__name__)
app.config.from_pyfile("config.py")
db = SQLAlchemy(app)
admin = Admin(app, name='demo', theme=Bootstrap4Theme(swatch='solar'))

# Define models
roles_users = db.Table(
"roles_users",
db.Column("user_id", db.Integer(), db.ForeignKey("user.id")),
db.Column("role_id", db.Integer(), db.ForeignKey("role.id")),
)


class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
first_name = db.Column(db.String(255))
last_name = db.Column(db.String(255))
email = db.Column(db.String(255), unique=True)
password = db.Column(db.String(255))
active = db.Column(db.Boolean())
confirmed_at = db.Column(db.DateTime())
roles = db.relationship(
"Role", secondary=roles_users, backref=db.backref("users", lazy="dynamic")
)
fs_uniquifier = db.Column(db.String(64), unique=True, nullable=False)

class Role(db.Model, RoleMixin):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30))
description = db.Column(db.String(255))

def __str__(self):
return self.name

class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(75), nullable=False)
content = db.Column(db.String(255), nullable=False)
created = db.Column(db.DateTime, default=datetime.utcnow)


user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app, user_datastore)

class UserView(ModelView):
def is_accessible(self):
return (
current_user.is_active
and current_user.is_authenticated
and current_user.has_role("superuser")
)

def _handle_view(self, name, **kwargs):
if not self.is_accessible():
if current_user.is_authenticated:
# permission denied
abort(403)
else:
# login
return redirect(url_for("security.login", next=request.url))
edit_modal = True


class PostView(ModelView):
def is_accessible(self):
return (
current_user.is_active
and current_user.is_authenticated
and current_user.has_role("superuser")
)

def _handle_view(self, name, **kwargs):
if not self.is_accessible():
if current_user.is_authenticated:
# permission denied
abort(403)
else:
# login
return redirect(url_for("security.login", next=request.url))
edit_modal = True

admin.add_view(UserView(User, db.session))
admin.add_view(PostView(Post, db.session))

def security_context_processor():
return dict(
admin_base_template=admin.theme.base_template,
admin_view=admin.index_view,
theme=admin.theme,
h=admin_helpers,
)



login_user.html

{% extends 'admin/master.html' %}

{% block body %}
<h1>Login</h1>
{% endblock %}



STACK TRACE

127.0.0.1 - - [26/Feb/2025 14:33:10] "GET /admin/login HTTP/1.1" 308 -
[2025-02-26 14:33:10,735] ERROR in app: Exception on /admin/login/ [GET]
Traceback (most recent call last):
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\app.py", line 1511, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\app.py", line 919, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\app.py", line 917, in full_dispatch_request
rv = self.dispatch_request()
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\app.py", line 902, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args) # type: ignore[no-any-return]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask_security\decorators.py", line 471, in decorated
return current_app.ensure_sync(fn)(*args, **kwargs)
~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask_security\views.py", line 233, in login
return _security.render_template(
~~~~~~~~~~~~~~~~~~~~~~~~~^
cv("LOGIN_USER_TEMPLATE"),
^^^^^^^^^^^^^^^^^^^^^^^^^^
...<2 lines>...
**_ctx("login"),
^^^^^^^^^^^^^^^^
)
^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask_security\utils.py", line 1189, in default_render_template
return render_template(*args, **kwargs)
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\templating.py", line 150, in render_template
return _render(app, template, context)
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\templating.py", line 131, in _render
rv = template.render(context)
File "C:\Users\Me\DemoApp\env\Lib\site-packages\jinja2\environment.py", line 1295, in render
self.environment.handle_exception()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\jinja2\environment.py", line 942, in handle_exception
raise rewrite_traceback_stack(source=source)
File "C:\Users\Me\DemoApp\templates\security\login_user.html", line 1, in top-level template code
{% extends 'admin/master.html' %}
^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask_admin\templates\bootstrap4\admin\master.html", line 1, in top-level template code
{% extends admin_base_template %}
^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\templating.py", line 65, in get_source
return self._get_source_fast(environment, template)
~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Me\DemoApp\env\Lib\site-packages\flask\templating.py", line 96, in _get_source_fast
return loader.get_source(environment, template)
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
a2\loaders.py", line 197, in get_source
pieces = split_template_path(template)
File "C:\Users\Me\DemoApp\env\Lib\site-packages\jinja2\loaders.py", line 30, in split_template_path
for piece in template.split("/"):
^^^^^^^^^^^^^^
jinja2.exceptions.UndefinedError: 'admin_base_template' is undefined
127.0.0.1 - - [26/Feb/2025 14:33:10] "GET /admin/login/ HTTP/1.1" 500 -


I had similar errors with the post_edit and user_edit templates which resolved after adding {% extends 'admin/<ModelName>/edit.html' %} into the mentioned html pages. From what I understand the login template is where it should be and it should only extend admin/master.html. I also tried by copying the login_user.html from the linked project above along with the macros/messages html in security folder and it still gives me the same error. I am kind of at a loss and would like to understand what I am missing as far as the admin_base_template error. Please halp

Edit

I am unsure what this means but after copying over the login_user.html from the source project and adding the decorator on security.context_processor it fails on the third line but boils down to the same error. I removed the line but it would fail on whatever I put there pointing first to the 3rd line then to the stack trace error of extends admin_base_template ... admin_base_template undefined.

For reference the line that I see changing in the stack trace is {% include "security/_messages.html" %} of login_user.html but if I remove that or add an empty newline it still says line 3.

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