Attempts to fix update_change_reason for nullable JSONField fields (issue #1181)

[martinschwinzerl]

Description

As reported in issue #1181, the implementation of the utility update_change_reason() method does not work for models with a nullable JSONField. This is caused by the slightly more convoluted querying mechanisms that has to be applied for JSONFields, please cf. here: django dev documentation

This attempts to fix this by checking

• if a field is a JSONField
• is nullable
• and then using different query language, depending on the null status of the field in question.

The strategy assumes that

• a nullable JSONField with a value of None is not set at all
• a non-nullable JSONField with a value of None is actually a "NULL" dictionary

Note: I am aware that this is not the only way to handle this. But it is the convention I am using in my project and this fixed the issue for me. It may be worthwhile to implement a policy switch to decide how to interpret None in this specific case.

Related Issue

• This attempts to fix issue Calling update_change_reason on a null JSONField with a postgres DB raise an AttributeError #1181

Motivation and Context

I did run into the same issue as the original reporter of the bug report and was stuck. The fix, while admittedly maybe not yet fully universal, depending on the interpretation of a "nullable" JSONField, did solve the issue for me

How Has This Been Tested?

Tested using my local installation. No unit test implemented but this can be done, if required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have run the pre-commit run command to format and lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have added my name and/or github handle to AUTHORS.rst
• I have added my change to CHANGES.rst
• All new and existing tests passed.

[martinschwinzerl]

Sorry, I had some issues with running the pre-commit hooks on my development machine as I do not have a python 3.8 environment available.

[INFO] Installing environment for https://github.com/psf/black.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
An unexpected error has occurred: CalledProcessError: command: ('/home/martin/.virtualenvs/ps_sps_users/bin/python', '-mvirtualenv', '/home/martin/.cache/pre-commit/repo5rnoh46q/py_env-python3.8', '-p', 'python3.8')
return code: 1
stdout:
    RuntimeError: failed to find interpreter for Builtin discover of python_spec='python3.8'
stderr: (none)
Check the log at /home/martin/.cache/pre-commit/pre-commit.log

I did locally modify the commit hooks to use python 3.11 and everything seemed to work but now my local branch contains this change to the pre-commit hooks and everything is a bit of a mess.

I am in a hurry but may have time to run again later next week on an older machine with python 3.8, any suggestions or pointers on how to handle this in a less awkward fashion would be highly appreciated!

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (29108a5) 96.87% compared to head (7ea2597) 96.56%.

Files	Patch %	Lines
simple_history/utils.py	20.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1282      +/-   ##
==========================================
- Coverage   96.87%   96.56%   -0.31%     
==========================================
  Files          23       23              
  Lines        1278     1282       +4     
  Branches      211      213       +2     
==========================================
  Hits         1238     1238              
- Misses         21       24       +3     
- Partials       19       20       +1     

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