16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
52 lines
2.0 KiB
Plaintext
52 lines
2.0 KiB
Plaintext
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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=== Message
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If "blank=True" is not set:
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Replace this "null=True" flag with "blank=True".
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If "blank=True" is set:
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Remove this "null=True" flag.
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'''
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endif::env-github,rspecator-view[] |