Crash on write of new instance when using GeneratedField

[Matt Hegarty]

We have an ​issue in django-import-export where imports of new instances fails when the model has a GeneratedField.

This occurs when an instance is being created which doesn't already exist in the database, which the ​docs imply is supported by GeneratedField:

A stored generated column is computed when it is written (inserted or updated)

The stack trace is attached.

Steps to reproduce:

1. Clone ​this repo and use the 'issue-1779-generatedfield' branch.
2. Create a ​venv
3. Install the example app following the instructions ​here
4. Navigate to "Books", click "Import", then select the attached sample.csv file.
5. Click "Submit" and you will see the error.

• python 3.12
• django 5.0.3

[Matt Hegarty]

sample csv for import

[Matt Hegarty]

stack trace

[Simon Charette]

This is similar to #35019 (fixed by 03af8fbd0f1cfc08edadda248cf5d3498e8ed2f7) but when dealing with instances that have a primary key assigned and force_insert is not specified.

When this is the case Mode.save ​will first attempt to perform an UPDATE as it cannot know whether or not the row exists.

It seems that the non_pk logic in _save_table needs to be adapted to also needs to exclude deferred fields when computing values for update purpose.

[Sarah Boyce <42296566+sarahboyce@…>]

In 8b53560e:

Fixed #35350 -- Fixed save() with pk set on models with GeneratedFields.

Thanks Matt Hegarty for the report and Simon Charette and Natalia Bidart for the reviews.

Regression in f333e35.

[Sarah Boyce <42296566+sarahboyce@…>]

In f075a19e:

[5.0.x] Fixed #35350 -- Fixed save() with pk set on models with GeneratedFields.

Thanks Matt Hegarty for the report and Simon Charette and Natalia Bidart for the reviews.

Regression in f333e35.

Backport of 8b53560eea9f10a1271d3bdf765dc6f969c7d9d5 from main.