Fix #72: LocalizedIntegerField should sort numerically, not lexicographically

localized_fields/fields/integer_field.py

@@ -1,6 +1,7 @@
 from typing import Dict, Optional, Union
 
 from django.conf import settings
+from django.contrib.postgres.fields.hstore import KeyTransform
 from django.db.utils import IntegrityError
 
 from ..forms import LocalizedIntegerFieldForm
@@ -8,17 +9,42 @@ from ..value import LocalizedIntegerValue, LocalizedValue
 from .field import LocalizedField
 
 
+class LocalizedIntegerFieldKeyTransform(KeyTransform):
+    """Transform that selects a single key from a hstore value and casts it to
+    an integer."""
+
+    def as_sql(self, compiler, connection):
+        sql, params = super().as_sql(compiler, connection)
+        return f"{sql}::integer", params
+
+
 class LocalizedIntegerField(LocalizedField):
     """Stores integers as a localized value."""
 
     attr_class = LocalizedIntegerValue
 
+    def get_transform(self, name):
+        """Gets the transformation to apply when selecting this value.
+
+        This is where the SQL expression to grab a single is added and
+        the cast to integer so that sorting by a hstore value works as
+        expected.
+        """
+
+        def _transform(*args, **kwargs):
+            return LocalizedIntegerFieldKeyTransform(name, *args, **kwargs)
+
+        return _transform
+
     @classmethod
     def from_db_value(cls, value, *_) -> Optional[LocalizedIntegerValue]:
         db_value = super().from_db_value(value)
         if db_value is None:
             return db_value
 
+        if isinstance(db_value, str):
+            return int(db_value)
+
         # if we were used in an expression somehow then it might be
         # that we're returning an individual value or an array, so
         # we should not convert that into an :see:LocalizedIntegerValue

tests/test_integer_field.py

@@ -1,3 +1,5 @@
+import django
+
 from django.conf import settings
 from django.db import connection
 from django.db.utils import IntegrityError
@@ -194,3 +196,33 @@ class LocalizedIntegerFieldTestCase(TestCase):
         )
         obj.refresh_from_db()
         assert obj.score.get(settings.LANGUAGE_CODE) == 75
+
+    def test_order_by(self):
+        """Tests whether ordering by a :see:LocalizedIntegerField key works
+        expected."""
+
+        # using key transforms (score__en) in order_by(..) is only
+        # supported since Django 2.1
+        # https://github.com/django/django/commit/2162f0983de0dfe2178531638ce7ea56f54dd4e7#diff-0edd853580d56db07e4020728d59e193
+
+        if django.VERSION < (2, 1):
+            return
+
+        model = get_fake_model(
+            {
+                "score": LocalizedIntegerField(
+                    default={settings.LANGUAGE_CODE: 1337}, null=True
+                )
+            }
+        )
+
+        model.objects.create(score=dict(en=982))
+        model.objects.create(score=dict(en=382))
+        model.objects.create(score=dict(en=1331))
+
+        res = list(
+            model.objects.values_list("score__en", flat=True).order_by(
+                "-score__en"
+            )
+        )
+        assert res == [1331, 982, 382]