Add LocalizedRef expression for extracting the value in the current language

localized_fields/expressions.py

@@ -0,0 +1,25 @@
+from django.conf import settings
+from django.utils import translation
+
+from psqlextra import expressions
+
+
+class LocalizedRef(expressions.HStoreRef):
+    """Expression that selects the value in a field only in
+    the currently active language."""
+
+    def __init__(self, name: str, lang: str=None):
+        """Initializes a new instance of :see:LocalizedRef.
+
+        Arguments:
+            name:
+                The field/column to select from.
+
+            lang:
+                The language to get the field/column in.
+                If not specified, the currently active language
+                is used.
+        """
+
+        language = lang or translation.get_language() or settings.LANGUAGE_CODE
+        super().__init__(name, language)

localized_fields/fields/field.py

@@ -82,6 +82,12 @@ class LocalizedField(HStoreField):
 
             return result
 
+        # this is for when you select an individual key, it will be string,
+        # not a dictionary, we'll give it to you as a flat value, not as a
+        # localized value instance
+        if not isinstance(value, dict):
+            return value
+
         return cls.attr_class(value)
 
     def to_python(self, value: Union[dict, str, None]) -> LocalizedValue:

tests/test_expressions.py

@@ -0,0 +1,65 @@
+from django.test import TestCase
+from django.db import models
+from django.utils import translation
+from django.conf import settings
+
+from localized_fields.fields import LocalizedField
+from localized_fields.value import LocalizedValue
+from localized_fields.expressions import LocalizedRef
+
+from .fake_model import get_fake_model
+
+
+class LocalizedExpressionsTestCase(TestCase):
+    """Tests whether expressions properly work with :see:LocalizedField."""
+
+    TestModel1 = None
+    TestModel2 = None
+
+    @classmethod
+    def setUpClass(cls):
+        """Creates the test model in the database."""
+
+        super(LocalizedExpressionsTestCase, cls).setUpClass()
+
+        cls.TestModel1 = get_fake_model(
+            'LocalizedExpressionsTestCase2',
+            {
+                'name': models.CharField(null=False, blank=False, max_length=255),
+            }
+        )
+
+        cls.TestModel2 = get_fake_model(
+            'LocalizedExpressionsTestCase1',
+            {
+                'text': LocalizedField(),
+                'other': models.ForeignKey(cls.TestModel1, related_name='features')
+            }
+        )
+
+    @classmethod
+    def test_localized_ref(cls):
+        """Tests whether the :see:LocalizedRef expression properly works."""
+
+        obj = cls.TestModel1.objects.create(name='bla bla')
+        for i in range(0, 10):
+            cls.TestModel2.objects.create(
+                text=LocalizedValue(dict(en='text_%d_en' % i, ro='text_%d_ro' % i, nl='text_%d_nl' % i)),
+                other=obj
+            )
+
+        for lang_code, _ in settings.LANGUAGES:
+            translation.activate(lang_code)
+
+            queryset = (
+                cls.TestModel1.objects
+                .annotate(
+                    mytexts=LocalizedRef('features__text')
+                )
+                .values_list(
+                    'mytexts', flat=True
+                )
+            )
+
+            for index, value in enumerate(queryset):
+                assert str(index) in value