/django-drf

name: django-drf
description: >
  Django REST Framework patterns.
  Trigger: When implementing generic DRF APIs (ViewSets, serializers, routers, permissions, filtersets). For Prowler API specifics (RLS/RBAC/Providers), also use prowler-api.
license: Apache-2.0
metadata:
  author: prowler-cloud
  version: "1.2.0"
  scope: [root, api]
  auto_invoke:
    - "Creating ViewSets, serializers, or filters in api/"
    - "Implementing JSON:API endpoints"
    - "Adding DRF pagination or permissions"
allowed-tools: Read, Edit, Write, Glob, Grep, Bash, WebFetch, WebSearch, Task

Critical Patterns

• ALWAYS separate serializers by operation: Read / Create / Update / Include
• ALWAYS use `filterset_class` for complex filtering (not `filterset_fields`)
• ALWAYS validate unknown fields in write serializers (inherit `BaseWriteSerializer`)
• ALWAYS use `select_related`/`prefetch_related` in `get_queryset()` to avoid N+1
• ALWAYS handle `swagger_fake_view` in `get_queryset()` for schema generation
• ALWAYS use `@extend_schema_field` for OpenAPI docs on `SerializerMethodField`
• NEVER put business logic in serializers - use services/utils
• NEVER use auto-increment PKs - use UUIDv4 or UUIDv7
• NEVER use trailing slashes in URLs (`trailing_slash=False`)

> **Note:** `swagger_fake_view` is specific to **drf-spectacular** for OpenAPI schema generation.

---

Implementation Checklist

When implementing a new endpoint, review these patterns in order:

| # | Pattern | Reference | Key Points | |---|---------|-----------|------------| | 1 | **Models** | `api/models.py` | UUID PK, `inserted_at`/`updated_at`, `JSONAPIMeta.resource_name` | | 2 | **ViewSets** | `api/base_views.py`, `api/v1/views.py` | Inherit `BaseRLSViewSet`, `get_queryset()` with N+1 prevention | | 3 | **Serializers** | `api/v1/serializers.py` | Separate Read/Create/Update/Include, inherit `BaseWriteSerializer` | | 4 | **Filters** | `api/filters.py` | Use `filterset_class`, inherit base filter classes | | 5 | **Permissions** | `api/base_views.py` | `required_permissions`, `set_required_permissions()` | | 6 | **Pagination** | `api/pagination.py` | Custom pagination class if needed | | 7 | **URL Routing** | `api/v1/urls.py` | `trailing_slash=False`, kebab-case paths | | 8 | **OpenAPI Schema** | `api/v1/views.py` | `@extend_schema_view` with drf-spectacular | | 9 | **Tests** | `api/tests/test_views.py` | JSON:API content type, fixture patterns |

> **Full file paths**: See [references/file-locations.md](references/file-locations.md)

---

Decision Trees

Which Serializer?

GET list/retrieve → <Model>Serializer
POST create       → <Model>CreateSerializer
PATCH update      → <Model>UpdateSerializer
?include=...      → <Model>IncludeSerializer

Which Base Serializer?

Read-only serializer   → BaseModelSerializerV1
Create with tenant_id  → RLSSerializer + BaseWriteSerializer (auto-injects tenant_id on create)
Update with validation → BaseWriteSerializer (tenant_id already exists on object)
Non-model data         → BaseSerializerV1

Which Filter Base?

Direct FK to Provider  → BaseProviderFilter
FK via Scan           → BaseScanProviderFilter
No provider relation  → FilterSet

Which Base ViewSet?

RLS-protected model  → BaseRLSViewSet (most common)
Tenant operations    → BaseTenantViewset
User operations      → BaseUserViewset
No RLS required      → BaseViewSet (rare)

Resource Name Format?

Single word model     → plural lowercase           (Provider → providers)
Multi-word model      → plural lowercase kebab     (ProviderGroup → provider-groups)
Through/join model    → parent-child pattern       (UserRoleRelationship → user-roles)
Aggregation/overview  → descriptive kebab plural   (ComplianceOverview → compliance-overviews)

---

Serializer Patterns

Base Class Hierarchy

# Read serializer (most common)
class ProviderSerializer(RLSSerializer):
    class Meta:
        model = Provider
        fields = ["id", "provider", "uid", "alias", "connected", "inserted_at"]

# Write serializer (validates unknown fields)
class ProviderCreateSerializer(RLSSerializer, BaseWriteSerializer):
    class Meta:
        model = Provider
        fields = ["provider", "uid", "alias"]

# Include serializer (sparse fields for ?include=)
class ProviderIncludeSerializer(RLSSerializer):
    class Meta:
        model = Provider
        fields = ["id", "alias"]  # Minimal fields

SerializerMethodField with OpenAPI

from drf_spectacular.utils import extend_schema_field

class ProviderSerializer(RLSSerializer):
    connection = serializers.SerializerMethodField(read_only=True)

    @extend_schema_field({
        "type": "object",
        "properties": {
            "connected": {"type": "boolean"},
            "last_checked_at": {"type": "string", "format": "date-time"},
        },
    })
    def get_connection(self, obj):
        return {
            "connected": obj.connected,
            "last_checked_at": obj.connection_last_checked_at,
        }

Included Serializers (JSON:API)

class ScanSerializer(RLSSerializer):
    included_serializers = {
        "provider": "api.v1.serializers.ProviderIncludeSerializer",
    }

Sensitive Data Masking

def to_representation(self, instance):
    data = super().to_representation(instance)
    # Mask by default, expose only on explicit request
    fields_param = self.context.get("request").query_params.get("fields[my-model]", "")
    if "api_key" in fields_param:
        data["api_key"] = instance.api_key_decoded
    else:
        data["api_key"] = "****" if instance.api_key else None
    return data

---

ViewSet Patterns

get_queryset() with N+1 Prevention

**Always combine** `swagger_fake_view` check with `select_related`/`prefetch_related`:

def get_queryset(self):
    # REQUIRED: Return empty queryset for OpenAPI schema generation
    if getattr(self, "swagger_fake