Fixed #36906 -- Handled coalescing JSON-primitive strings and JSON values on Oracle.

3 files changed, 20 insertions, 4 deletions

diff --git a/django/db/models/functions/comparison.py b/django/db/models/functions/comparison.py
index 8f7493f2fd..5827925e6e 100644
--- a/django/db/models/functions/comparison.py
+++ b/django/db/models/functions/comparison.py
@@ -86,9 +86,10 @@ class Coalesce(Func):
         return None
 
     def as_oracle(self, compiler, connection, **extra_context):
-        # Oracle prohibits mixing TextField (NCLOB) and CharField (NVARCHAR2),
-        # so convert all fields to NCLOB when that type is expected.
-        if self.output_field.get_internal_type() == "TextField":
+        # Oracle prohibits mixing TextField, JSONField (NCLOB) and CharField
+        # (NVARCHAR2), so convert all fields to NCLOB when that type is
+        # expected.
+        if self.output_field.get_internal_type() in ("TextField", "JSONField"):
             clone = self.copy()
             clone.set_source_expressions(
                 [
diff --git a/tests/model_fields/models.py b/tests/model_fields/models.py
index a594b89adb..c1e356bb53 100644
--- a/tests/model_fields/models.py
+++ b/tests/model_fields/models.py
@@ -452,6 +452,7 @@ class JSONNullDefaultModel(models.Model):
 class RelatedJSONModel(models.Model):
     value = models.JSONField()
     json_model = models.ForeignKey(NullableJSONModel, models.CASCADE)
+    summary = models.CharField(max_length=100, null=True, blank=True)
 
     class Meta:
         required_db_features = {"supports_json_field"}
diff --git a/tests/model_fields/test_jsonfield.py b/tests/model_fields/test_jsonfield.py
index 1afeef31eb..7b07a48a1e 100644
--- a/tests/model_fields/test_jsonfield.py
+++ b/tests/model_fields/test_jsonfield.py
@@ -40,7 +40,7 @@ from django.db.models.fields.json import (
     KeyTransformFactory,
     KeyTransformTextLookupMixin,
 )
-from django.db.models.functions import Cast
+from django.db.models.functions import Cast, Coalesce
 from django.test import (
     SimpleTestCase,
     TestCase,
@@ -1290,6 +1290,20 @@ class TestQuerying(TestCase):
         )
         self.assertQuerySetEqual(qs, all_objects)
 
+    @skipUnlessDBFeature("supports_primitives_in_json_field")
+    def test_json_type_casting_with_coalesce(self):
+        RelatedJSONModel.objects.create(
+            summary='"This is valid JSON primitive."',
+            value={"text": "test"},
+            json_model=self.objs[4],
+        )
+        result = RelatedJSONModel.objects.annotate(
+            coalesced_value=Coalesce(
+                Cast("summary", JSONField()), "value", output_field=JSONField()
+            )
+        ).first()
+        self.assertEqual(result.coalesced_value, "This is valid JSON primitive.")
+
 
 @skipUnlessDBFeature("supports_primitives_in_json_field")
 class JSONNullTests(TestCase):