Fixed #35718 -- Add JSONArray to django.db.models.functions.

Co-authored-by: Sarah Boyce <42296566+sarahboyce@users.noreply.github.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

django/db/models/functions/__init__.py

@@ -25,7 +25,7 @@ from .datetime import (
     TruncWeek,
     TruncYear,
 )
-from .json import JSONObject
+from .json import JSONArray, JSONObject
 from .math import (
     Abs,
     ACos,
@@ -126,6 +126,7 @@ __all__ = [
     "TruncWeek",
     "TruncYear",
     # json
+    "JSONArray",
     "JSONObject",
     # math
     "Abs",

django/db/models/functions/json.py

@@ -5,6 +5,66 @@ from django.db.models.fields.json import JSONField
 from django.db.models.functions import Cast
 
 
+class JSONArray(Func):
+    function = "JSON_ARRAY"
+    output_field = JSONField()
+
+    def as_sql(self, compiler, connection, **extra_context):
+        if not connection.features.supports_json_field:
+            raise NotSupportedError(
+                "JSONFields are not supported on this database backend."
+            )
+        return super().as_sql(compiler, connection, **extra_context)
+
+    def as_native(self, compiler, connection, *, returning, **extra_context):
+        # PostgreSQL 16+ and Oracle remove SQL NULL values from the array by
+        # default. Adds the NULL ON NULL clause to keep NULL values in the
+        # array, mapping them to JSON null values, which matches the behavior
+        # of SQLite.
+        null_on_null = "NULL ON NULL" if len(self.get_source_expressions()) > 0 else ""
+
+        return self.as_sql(
+            compiler,
+            connection,
+            template=(
+                f"%(function)s(%(expressions)s {null_on_null} RETURNING {returning})"
+            ),
+            **extra_context,
+        )
+
+    def as_postgresql(self, compiler, connection, **extra_context):
+        # Casting source expressions is only required using JSONB_BUILD_ARRAY
+        # or when using JSON_ARRAY on PostgreSQL 16+ with server-side bindings.
+        # This is done in all cases for consistency.
+        casted_obj = self.copy()
+        casted_obj.set_source_expressions(
+            [
+                (
+                    # Conditional Cast to avoid unnecessary wrapping.
+                    expression
+                    if isinstance(expression, Cast)
+                    else Cast(expression, expression.output_field)
+                )
+                for expression in casted_obj.get_source_expressions()
+            ]
+        )
+
+        if connection.features.is_postgresql_16:
+            return casted_obj.as_native(
+                compiler, connection, returning="JSONB", **extra_context
+            )
+
+        return casted_obj.as_sql(
+            compiler,
+            connection,
+            function="JSONB_BUILD_ARRAY",
+            **extra_context,
+        )
+
+    def as_oracle(self, compiler, connection, **extra_context):
+        return self.as_native(compiler, connection, returning="CLOB", **extra_context)
+
+
 class JSONObject(Func):
     function = "JSON_OBJECT"
     output_field = JSONField()

docs/ref/models/database-functions.txt

@@ -841,6 +841,33 @@ that deal with time-parts can be used with ``TimeField``:
 JSON Functions
 ==============
 
+``JSONArray``
+-------------
+
+.. versionadded:: 5.2
+
+.. class:: JSONArray(*expressions)
+
+Accepts a list of field names or expressions and returns a JSON array
+containing those values.
+
+Usage example:
+
+.. code-block:: pycon
+
+    >>> from django.db.models import F
+    >>> from django.db.models.functions import JSONArray, Lower
+    >>> Author.objects.create(name="Margaret Smith", alias="msmith", age=25)
+    >>> author = Author.objects.annotate(
+    ...     json_array=JSONArray(
+    ...         Lower("name"),
+    ...         "alias",
+    ...         F("age") * 2,
+    ...     )
+    ... ).get()
+    >>> author.json_array
+    ['margaret smith', 'msmith', 50]
+
 ``JSONObject``
 --------------
 

docs/releases/5.2.txt

@@ -326,6 +326,10 @@ Models
 * :meth:`.QuerySet.explain` now supports the ``memory`` and ``serialize``
   options on PostgreSQL 17+.
 
+* The new :class:`~django.db.models.functions.JSONArray` database function
+  accepts a list of field names or expressions and returns a JSON array
+  containing those values.
+
 Requests and Responses
 ~~~~~~~~~~~~~~~~~~~~~~
 

tests/db_functions/json/test_json_array.py

@@ -0,0 +1,177 @@
+import unittest
+
+from django.db import NotSupportedError, connection
+from django.db.models import CharField, F, Value
+from django.db.models.functions import Cast, JSONArray, JSONObject, Lower
+from django.test import TestCase
+from django.test.testcases import skipIfDBFeature, skipUnlessDBFeature
+from django.utils import timezone
+
+from ..models import Article, Author
+
+
+@skipUnlessDBFeature("supports_json_field")
+class JSONArrayTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        Author.objects.create(name="Ivan Ivanov", alias="iivanov")
+
+    def test_empty(self):
+        obj = Author.objects.annotate(json_array=JSONArray()).first()
+        self.assertEqual(obj.json_array, [])
+
+    def test_basic(self):
+        obj = Author.objects.annotate(
+            json_array=JSONArray(Value("name"), F("name"))
+        ).first()
+        self.assertEqual(obj.json_array, ["name", "Ivan Ivanov"])
+
+    def test_expressions(self):
+        obj = Author.objects.annotate(
+            json_array=JSONArray(
+                Lower("name"),
+                F("alias"),
+                F("goes_by"),
+                Value(30000.15),
+                F("age") * 2,
+            )
+        ).first()
+        self.assertEqual(
+            obj.json_array,
+            [
+                "ivan ivanov",
+                "iivanov",
+                None,
+                30000.15,
+                60,
+            ],
+        )
+
+    def test_nested_json_array(self):
+        obj = Author.objects.annotate(
+            json_array=JSONArray(
+                F("name"),
+                JSONArray(F("alias"), F("age")),
+            )
+        ).first()
+        self.assertEqual(
+            obj.json_array,
+            [
+                "Ivan Ivanov",
+                ["iivanov", 30],
+            ],
+        )
+
+    def test_nested_empty_json_array(self):
+        obj = Author.objects.annotate(
+            json_array=JSONArray(
+                F("name"),
+                JSONArray(),
+            )
+        ).first()
+        self.assertEqual(
+            obj.json_array,
+            [
+                "Ivan Ivanov",
+                [],
+            ],
+        )
+
+    def test_textfield(self):
+        Article.objects.create(
+            title="The Title",
+            text="x" * 4000,
+            written=timezone.now(),
+        )
+        obj = Article.objects.annotate(json_array=JSONArray(F("text"))).first()
+        self.assertEqual(obj.json_array, ["x" * 4000])
+
+    @unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests")
+    def test_explicit_cast(self):
+        qs = Author.objects.annotate(
+            json_array=JSONArray(Cast("age", CharField()))
+        ).values("json_array")
+        with self.assertNumQueries(1) as ctx:
+            self.assertSequenceEqual(qs, [{"json_array": ["30"]}])
+        sql = ctx.captured_queries[0]["sql"]
+        self.assertIn("::varchar", sql)
+        self.assertNotIn("::varchar)::varchar", sql)
+
+    def test_order_by_key(self):
+        qs = Author.objects.annotate(arr=JSONArray(F("alias"))).order_by("arr__0")
+        self.assertQuerySetEqual(qs, Author.objects.order_by("alias"))
+
+    def test_order_by_nested_key(self):
+        qs = Author.objects.annotate(arr=JSONArray(JSONArray(F("alias")))).order_by(
+            "-arr__0__0"
+        )
+        self.assertQuerySetEqual(qs, Author.objects.order_by("-alias"))
+
+
+@skipIfDBFeature("supports_json_field")
+class JSONArrayNotSupportedTests(TestCase):
+    def test_not_supported(self):
+        msg = "JSONFields are not supported on this database backend."
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            Author.objects.annotate(json_array=JSONArray()).first()
+
+
+@skipUnlessDBFeature("has_json_object_function", "supports_json_field")
+class JSONArrayObjectTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        Author.objects.create(name="Ivan Ivanov", alias="iivanov")
+
+    def test_nested_json_array_object(self):
+        obj = Author.objects.annotate(
+            json_array=JSONArray(
+                JSONObject(
+                    name1="name",
+                    nested_json_object1=JSONObject(alias1="alias", age1="age"),
+                ),
+                JSONObject(
+                    name2="name",
+                    nested_json_object2=JSONObject(alias2="alias", age2="age"),
+                ),
+            )
+        ).first()
+        self.assertEqual(
+            obj.json_array,
+            [
+                {
+                    "name1": "Ivan Ivanov",
+                    "nested_json_object1": {"alias1": "iivanov", "age1": 30},
+                },
+                {
+                    "name2": "Ivan Ivanov",
+                    "nested_json_object2": {"alias2": "iivanov", "age2": 30},
+                },
+            ],
+        )
+
+    def test_nested_json_object_array(self):
+        obj = Author.objects.annotate(
+            json_object=JSONObject(
+                name="name",
+                nested_json_array=JSONArray(
+                    JSONObject(alias1="alias", age1="age"),
+                    JSONObject(alias2="alias", age2="age"),
+                ),
+            )
+        ).first()
+        self.assertEqual(
+            obj.json_object,
+            {
+                "name": "Ivan Ivanov",
+                "nested_json_array": [
+                    {"alias1": "iivanov", "age1": 30},
+                    {"alias2": "iivanov", "age2": 30},
+                ],
+            },
+        )
+
+    def test_order_by_nested_key(self):
+        qs = Author.objects.annotate(
+            arr=JSONArray(JSONObject(alias=F("alias")))
+        ).order_by("-arr__0__alias")
+        self.assertQuerySetEqual(qs, Author.objects.order_by("-alias"))