47 lines
1.9 KiB
Plaintext
47 lines
1.9 KiB
Plaintext
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This rule suggests avoiding the use of "null=True" on string-based fields such as CharField and TextField in Django models. Instead, it recommends using blank=True, which allows an empty string as a valid value while still maintaining the ability to query and filter on the field.
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== Why is this an issue?
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Using "null=True" on string-based fields can lead to inconsistent and unexpected behavior. In Django, "null=True" allows the field to have a NULL value in the database. However, the Django convention to represent the absence of data for a string is an empty string. Having two ways to represent the absence of data can cause problems when querying and filtering on the field. For example, if a CharField with "null=True" has a value of NULL in the database, querying for an empty string will not return that object.
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== How to fix it
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Instead of using "null=True", use "blank=True" on string-based fields such as CharField and TextField. This allows an empty string as a valid value while still maintaining the ability to query and filter on the field. If a field should not be left empty, specify a default value using the default argument.
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=== Code examples
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==== Noncompliant code example
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[source,python]
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----
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class ExampleModel(models.Model):
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name = models.CharField(max_length=50, null=True)
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----
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==== Compliant solution
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[source,python]
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----
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class ExampleModel(models.Model):
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name = models.CharField(max_length=50, blank=True)
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----
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== Exceptions
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If `unique=True` and `blank=True` are both set, `null=True` is required to avoid unique constraint violations when saving multiple objects with blank values. No issue will be raised in this scenario.
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== Resources
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=== Documentation
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https://docs.djangoproject.com/en/4.1/ref/models/fields[Django model field reference]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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include::message.adoc[]
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'''
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endif::env-github,rspecator-view[]
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