different hashing in release_feedback and fetch_feedback

Operating system

Ubuntu 20.04.5 LTS

nbgrader --version

0.8.0

jupyterhub --version (if used with JupyterHub)

2.3.1

jupyter notebook --version

6.4.12

jupyter lab --version

3.4.6

Expected behavior

same result from notebook_hash in release_feedback.py and fetch_feedback.py

Actual behavior

different results, resulting in [FetchFeedbackApp | WARNING] Could not find feedback for ... during nbgrader fetch_feedback --debug

Steps to reproduce the behavior

As instructor do nbgrader release_feedback --debug <assignment>. Then as student do nbgradere fetch_feedback --debug <assignment>.

Explanation

We are using nbgrader with jupyterhub and jupyter lab for one of our courses much to our liking. For several months all was working well but very recently we stumbled on the following incident. Two students (of 20) are not able to fetch the feedback of one particular assignment.

After some debugging I found that the hash in release_feedback.py was generated with different values than in fetch_feedback.py:

nbgrader release_feedback --debug 'Assignment 3 Wavefront sensing

[ReleaseFeedbackApp | DEBUG] nbfile is: /home/grader-ap3122/ap3122/submitted/<username>/Assignment 3 Wavefront sensing/Assignment Wavefront aberrations.ipynb
[ReleaseFeedbackApp | DEBUG] Unique key is: ap3122+Assignment 3 Wavefront sensing+Assignment Wavefront aberrations+<username>[phone]:17:36.574853 UTC
[ReleaseFeedbackApp | DEBUG] checksum is: f9990f2f5f029af5091cbc417c5a591e
[ReleaseFeedbackApp | DEBUG] dest is: /usr/local/share/nbgrader/exchange/ap3122/feedback/f9990f2f5f029af5091cbc417c5a591e.html

nbgrader fetch_feedback --debug 'Assignment 3 Wavefront sensing

[FetchFeedbackApp | DEBUG] notebook is: /data/jupyterhub/home/<username>/.local/share/jupyter/nbgrader_cache/ap3122/<username>+Assignment 3 Wavefront sensing+2022-11-11 15:17:36.574853 UTC/Assignment Wavefront aberrations.ipynb
[FetchFeedbackApp | DEBUG] Unique key is: ap3122+Assignment 3 Wavefront sensing+Assignment Wavefront aberrations+<username>[phone]:17:36.574853 UTC
[FetchFeedbackApp | DEBUG] nb_hash is: 209d0cfb1a1a05ba8d64273f2fd04271
[FetchFeedbackApp | DEBUG] feedbackpath is: /usr/local/share/nbgrader/exchange/ap3122/feedback/209d0cfb1a1a05ba8d64273f2fd04271.html

the student name has been replaced with <username>

I’ve added some debugging code to the two python-scripts logging the values of the appropriate variables

Clearly the nbfile and notebook have very different value resulting in different hash values. This is reflected in the different values of dest and feedbackpath which should be the same.

[perllaghu]

Ah… my apologies - I miss-read the original.

Let me have a look-see - I would be surprised if this was not just two different names for the same string… but I’ll check

[ykazakov]

@ronligt We have experienced a similar problem, which could be traced to the following situation:

• students produce corrupted notebooks, e.g., by deleting or duplicating answer cells
• nbgrader refuses to auto-grade such submissions, so instructors “fix” the submitted versions of the students (copied from the exchange)
• the feedback is generated against the modified submission, so students could not fetch feedback because of the different hash value, which is a part of the feedback file name (students are not permitted to list files in the exchange directory, but if they “know” the file name of the feedback, they can copy it)