Document that fields cannot be named 'check'

[Francisco Camerini]

I've been tasked with migrating a large codebase from Django 3.2 to 4.2.

Upon updating to 4.0, I noticed that the ​models.E020 system check was being triggered.

This project has had multiple models with "check" fields for many years. This error was not being triggered before 4.0 because class methods were protected from being overwritten by fields. This behavior ​was changed here

​This commit's message is very explicit about "check" being a reserved word that cannot be redefined as anything else other than a method. However, the ​documentation on field name restrictions is silent about that, only stating that:

• A field name cannot be a Python reserved word, because that would result in a Python syntax error.
• A field name cannot contain more than one underscore in a row, due to the way Django’s query lookup syntax works.
• A field name cannot end with an underscore.

For now I've silenced the models.E020 error, but this is far from ideal, what would be the best way to still run all model system checks without having to change our models to use a different field name?

[Sarah Boyce]

For context, this check was introduced in ​Django 1.7.1. I agree that fields are not allowed to be called check should be added to the ​documentation on field names 👍
I am going to slightly repurpose and accept this ticket for this.

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Replying to Francisco Camerini:

For now I've silenced the models.E020 error, but this is far from ideal, what would be the best way to still run all model system checks without having to change our models to use a different field name?

I am not sure there is another option. I think that this check wasn't being raised before might have been down to the model hierarchy structure (hard to tell without seeing the models - refs #30427, #16176). You may have to update the field names and set db_column="check". You might get more support if you were to ask this on one of our ​support channels

[Mohammad Salehi]

I have created a PR: ​https://github.com/django/django/pull/18465

[Sarah Boyce <42296566+sarahboyce@…>]

In ca47884:

Fixed #35623 -- Documented that a field cannot be named 'check'.