✨ Use DRF field info to extract filter param model field

Author: sergei-maertens

vng_api_common/inspectors/query.py

@@ -1,4 +1,3 @@
-from django.core.exceptions import FieldDoesNotExist
 from django.db import models
 from django.utils.encoding import force_text
 from django.utils.translation import ugettext as _
@@ -10,6 +9,7 @@
 
 from ..filters import URLModelChoiceFilter
 from ..utils import underscore_to_camel
+from .utils import get_target_field
 
 
 class FilterInspector(CoreAPICompatInspector):
@@ -29,13 +29,7 @@ def get_filter_parameters(self, filter_backend):
 
             for parameter in fields:
                 filter_field = filter_class.base_filters[parameter.name]
-
-                try:
-                    model_field = queryset.model._meta.get_field(
-                        parameter.name.split("__")[0]
-                    )
-                except FieldDoesNotExist:
-                    model_field = None
+                model_field = get_target_field(queryset.model, parameter.name)
 
                 help_text = filter_field.extra.get(
                     "help_text", model_field.help_text if model_field else ""

vng_api_common/inspectors/utils.py

@@ -0,0 +1,40 @@
+from typing import Optional, Type
+
+from django.db import models
+
+from rest_framework.utils.model_meta import get_field_info
+
+
+def get_target_field(model: Type[models.Model], field: str) -> Optional[models.Field]:
+    """
+    Retrieve the end-target that ``field`` points to.
+
+    :param field: A string containing a lookup, potentially spanning relations. E.g.:
+      foo__bar__lte.
+    :return: A Django model field instance or `None`
+    """
+
+    start, *remaining = field.split("__")
+    field_info = get_field_info(model)
+
+    # simple, non relational field?
+    if start in field_info.fields:
+        return field_info.fields[start]
+
+    # simple relational field?
+    if start in field_info.forward_relations:
+        relation_info = field_info.forward_relations[start]
+        if not remaining:
+            return relation_info.model_field
+        else:
+            return get_target_field(relation_info.related_model, "__".join(remaining))
+
+    # check the reverse relations - note that the model name is used instead of model_name_set
+    # in the queries -> we can't just test for containment in field_info.reverse_relations
+    for relation_info in field_info.reverse_relations.values():
+        # not sure about this - what if there are more relations with different related names?
+        if relation_info.related_model._meta.model_name != start:
+            continue
+        return get_target_field(relation_info.related_model, "__".join(remaining))
+
+    return None