Refs #31211 -- Prevented SearchConfig nesting in SearchVector and SearchQuery init.

Passing a SearchConfig instance directly to SearchVector and
SearchQuery would result in nested SearchConfig instance.

django/contrib/postgres/search.py

@@ -41,6 +41,12 @@ class SearchConfig(Expression):
             config = Value(config)
         self.config = config
 
+    @classmethod
+    def from_parameter(cls, config):
+        if config is None or isinstance(config, cls):
+            return config
+        return cls(config)
+
     def get_source_expressions(self):
         return [self.config]
 
@@ -75,7 +81,7 @@ class SearchVector(SearchVectorCombinable, Func):
     def __init__(self, *expressions, **extra):
         super().__init__(*expressions, **extra)
         config = self.extra.get('config', self.config)
-        self.config = SearchConfig(config) if config else None
+        self.config = SearchConfig.from_parameter(config)
         weight = self.extra.get('weight')
         if weight is not None and not hasattr(weight, 'resolve_expression'):
             weight = Value(weight)
@@ -162,7 +168,7 @@ class SearchQuery(SearchQueryCombinable, Value):
     }
 
     def __init__(self, value, output_field=None, *, config=None, invert=False, search_type='plain'):
-        self.config = SearchConfig(config) if config else None
+        self.config = SearchConfig.from_parameter(config)
         self.invert = invert
         if search_type not in self.SEARCH_TYPES:
             raise ValueError("Unknown search_type argument '%s'." % search_type)

tests/postgres_tests/test_search.py

@@ -6,13 +6,13 @@ All text copyright Python (Monty) Pictures. Thanks to sacred-texts.com for the
 transcript.
 """
 from django.contrib.postgres.search import (
-    SearchQuery, SearchRank, SearchVector,
+    SearchConfig, SearchQuery, SearchRank, SearchVector,
 )
 from django.db import connection
 from django.db.models import F
 from django.test import SimpleTestCase, modify_settings, skipUnlessDBFeature
 
-from . import PostgreSQLTestCase
+from . import PostgreSQLSimpleTestCase, PostgreSQLTestCase
 from .models import Character, Line, Scene
 
 
@@ -118,6 +118,13 @@ class SearchVectorFieldTest(GrailTestData, PostgreSQLTestCase):
         self.assertNotIn('COALESCE(COALESCE', str(searched.query))
 
 
+class SearchConfigTests(PostgreSQLSimpleTestCase):
+    def test_from_parameter(self):
+        self.assertIsNone(SearchConfig.from_parameter(None))
+        self.assertEqual(SearchConfig.from_parameter('foo'), SearchConfig('foo'))
+        self.assertEqual(SearchConfig.from_parameter(SearchConfig('bar')), SearchConfig('bar'))
+
+
 class MultipleFieldsTest(GrailTestData, PostgreSQLTestCase):
 
     def test_simple_on_dialogue(self):