Refs #24928 -- Added introspection support for PostgreSQL JSONField

Thanks Adam Johnson and Tim Graham for the reviews.

tests/postgres_tests/test_introspection.py

@@ -0,0 +1,26 @@
+from io import StringIO
+
+from django.core.management import call_command
+from django.test.utils import modify_settings
+
+from . import PostgreSQLTestCase
+
+
+@modify_settings(INSTALLED_APPS={'append': 'django.contrib.postgres'})
+class InspectDBTests(PostgreSQLTestCase):
+    def assertFieldsInModel(self, model, field_outputs):
+        out = StringIO()
+        call_command(
+            'inspectdb',
+            table_name_filter=lambda tn: tn.startswith(model),
+            stdout=out,
+        )
+        output = out.getvalue()
+        for field_output in field_outputs:
+            self.assertIn(field_output, output)
+
+    def test_json_field(self):
+        self.assertFieldsInModel(
+            'postgres_tests_jsonmodel',
+            ['field = django.contrib.postgresql.fields.JSONField(blank=True, null=True)'],
+        )