ensure metadata is dict in all cases (#6646)

Author: escattone

kitsune/products/admin.py

@@ -1,5 +1,6 @@
 from typing import Any
 
+from django import forms
 from django.contrib import admin
 from django.db.models.query import QuerySet
 from django.http import HttpRequest
@@ -14,6 +15,24 @@
 )
 
 
+class DictOnlyJSONField(forms.JSONField):
+    def to_python(self, value):
+        if value in self.empty_values:
+            return {}  # Convert an empty input value into an empty dict.
+        result = super().to_python(value)
+        if not isinstance(result, dict):
+            raise forms.ValidationError("Value must be a JSON object (dict).")
+        return result
+
+
+class TopicAdminForm(forms.ModelForm):
+    metadata = DictOnlyJSONField(required=False)
+
+    class Meta:
+        model = Topic
+        fields = "__all__"
+
+
 class ArchivedFilter(admin.SimpleListFilter):
     title = "Archived status"
     parameter_name = "is_archived"
@@ -71,6 +90,8 @@ def parent(obj):
     def get_products(obj):
         return ", ".join([p.title for p in obj.products.all()])
 
+    form = TopicAdminForm
+
     parent.short_description = "Parent"  # type: ignore
     get_products.short_description = "Products"  # type: ignore
 

kitsune/products/models.py

@@ -182,6 +182,12 @@ def save(self, *args, **kwargs):
                 cache_key = f"hierarchical_topics_{product.slug}"
                 cache.delete(cache_key)
 
+        # Ensure that the "metadata" field is a dict.
+        if self.metadata is None:
+            self.metadata = {}
+        elif not isinstance(self.metadata, dict):
+            raise ValueError('The "metadata" field must be a dict.')
+
         super().save(*args, **kwargs)
         self._topic_is_archived = self.is_archived