TypeError: object of type 'NoneType' has no len()

[mplewis]

Hello! I'm having trouble using Excalibur out of the box.

What I did

Installed Excalibur and set it up:

pip install excalibur-py
excalibur initdb
excalibur webserver

Then, uploaded a PDF via the web interface.

Expected behavior

Excalibur extracts data from my PDF for me.

Actual behavior

I receive a 500 Internal Server Error at http://localhost:5000/workspaces/c644cced-85fe-42a7-92c9-aa6dcc6fc72a:

❯ excalibur webserver
 * Serving Flask app 'excalibur.www.app'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET / HTTP/1.1" 302 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /files HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/css/vendor/bootstrap.min.css HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/js/vendor/jquery-3.3.1.min.js HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/css/base.css HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/js/vendor/popper.min.js HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/js/vendor/bootstrap.min.js HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/js/files.js HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:05] "GET /static/favicon.ico HTTP/1.1" 200 -
127.0.0.1 - - [08/Jan/2025 11:40:12] "POST /files HTTP/1.1" 200 -
[2025-01-08 11:40:12,401] ERROR in app: Exception on /workspaces/c644cced-85fe-42a7-92c9-aa6dcc6fc72a [GET]
Traceback (most recent call last):
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/flask/app.py", line 1511, in wsgi_app
    response = self.full_dispatch_request()
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/flask/app.py", line 919, in full_dispatch_request
    rv = self.handle_user_exception(e)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/flask/app.py", line 917, in full_dispatch_request
    rv = self.dispatch_request()
         ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/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 "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/excalibur/www/views.py", line 106, in workspaces
    return render_template(
           ^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/flask/templating.py", line 150, in render_template
    return _render(app, template, context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/flask/templating.py", line 131, in _render
    rv = template.render(context)
         ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/jinja2/environment.py", line 1295, in render
    self.environment.handle_exception()
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/jinja2/environment.py", line 942, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/excalibur/www/templates/workspace.html", line 1, in top-level template code
    {% extends "base.html" %}
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/excalibur/www/templates/base.html", line 61, in top-level template code
    {% block workspace %}{% endblock %}
    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/mplewis/.local/share/mise/installs/python/3.12.7/lib/python3.12/site-packages/excalibur/www/templates/workspace.html", line 12, in block 'workspace'
    {% if imagepaths is not none or imagepaths|length == 0 %}
    ^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: object of type 'NoneType' has no len()
127.0.0.1 - - [08/Jan/2025 11:40:12] "GET /workspaces/c644cced-85fe-42a7-92c9-aa6dcc6fc72a HTTP/1.1" 500 -

Versions

>>> import platform; print(platform.platform())
macOS-15.2-arm64-arm-64bit
>>> import sys; print('Python', sys.version)
Python 3.12.7 (main, Oct  2 2024, 15:45:55) [Clang 18.1.8 ]
>>> import numpy; print('NumPy', numpy.__version__)
NumPy 2.2.1
>>> import cv2; print('OpenCV', cv2.__version__)
OpenCV 4.10.0
>>> import excalibur; print('Excalibur', excalibur.__version__)
Excalibur 1.0.1

Let me know if I can provide any more info to help you replicate this issue. Thanks!