mcp-server-semgrep/semgrep-rules/python/django/correctness/string-field-null-checks.yaml

MCP Server for Semgrep Integration - static code analysis with AI

rules:
  - id: no-null-string-field
    patterns:
      - pattern-inside: |
          class $M(...):
            ...
      - pattern-not: $F = django.db.models.CharField(..., null=True, unique=True, blank=True, ...)
      - pattern-not: $F = django.db.models.TextField(..., null=True, unique=True, blank=True, ...)
      - pattern-either:
          - pattern: $F = django.db.models.CharField(..., null=True, ...)
          - pattern: $F = django.db.models.TextField(..., null=True, ...)
    message: >-
      Avoid using null on string-based fields such as CharField and TextField. If a string-based field
      has null=True, that means it has two possible values for "no data": NULL, and the empty string. In
      most cases, it's redundant to have two possible values for "no data;" the Django convention is to
      use the empty string, not NULL.
    languages: [python]
    severity: WARNING
    metadata:
      category: correctness
      technology:
        - django
  - id: string-field-must-set-null-true
    patterns:
      - pattern-inside: |
          class $M(...):
            ...
      - pattern-not: $F = django.db.models.CharField(..., unique=True, blank=True, null=True, ...)
      - pattern-not: $F = django.db.models.TextField(..., unique=True, blank=True, null=True, ...)
      - pattern-either:
          - pattern: $F = django.db.models.CharField(..., unique=True, blank=True, ...)
          - pattern: $F = django.db.models.TextField(..., unique=True, blank=True, ...)
    message:
      If a text field declares unique=True and blank=True, null=True must also be set to avoid unique constraint violations
      when saving multiple objects with blank values.
    languages: [python]
    severity: ERROR
    metadata:
      category: correctness
      technology:
        - django