Tests invalid search operators and removes a useless check.

wagtail/wagtailsearch/backends/base.py

@@ -279,12 +279,6 @@ class BaseSearchBackend(object):
             for prefetch in prefetch_related:
                 queryset = queryset.prefetch_related(prefetch)
 
-        # Check operator
-        if operator is not None:
-            operator = operator.lower()
-            if operator not in ['or', 'and']:
-                raise ValueError("operator must be either 'or' or 'and'")
-
         # Search
         search_query = self.query_compiler_class(
             queryset, query, fields=fields, operator=operator, order_by_relevance=order_by_relevance

wagtail/wagtailsearch/query.py

@@ -138,9 +138,9 @@ class PlainText(SearchQueryShortcut):
     def __init__(self, query_string: str, operator: str = DEFAULT_OPERATOR,
                  boost: float = 1):
         self.query_string = query_string
-        if operator.lower() not in self.OPERATORS:
+        self.operator = operator.lower()
+        if self.operator not in self.OPERATORS:
             raise ValueError("`operator` must be either 'or' or 'and'.")
-        self.operator = operator
         self.boost = boost
 
     def apply(self, func):

wagtail/wagtailsearch/tests/test_backends.py

@@ -538,6 +538,36 @@ class BackendTests(WagtailTestUtils):
         self.assertSetEqual({r.title for r in results},
                             {'JavaScript: The Definitive Guide'})
 
+    def test_plain_text_operator_case(self):
+        results = self.backend.search(PlainText('Guide', operator='AND'),
+                                      models.Book.objects.all())
+        self.assertSetEqual({r.title for r in results},
+                            {'JavaScript: The Definitive Guide'})
+
+        results = self.backend.search(PlainText('Guide', operator='aNd'),
+                                      models.Book.objects.all())
+        self.assertSetEqual({r.title for r in results},
+                            {'JavaScript: The Definitive Guide'})
+
+        results = self.backend.search('Guide', models.Book.objects.all(),
+                                      operator='AND')
+        self.assertSetEqual({r.title for r in results},
+                            {'JavaScript: The Definitive Guide'})
+
+        results = self.backend.search('Guide', models.Book.objects.all(),
+                                      operator='aNd')
+        self.assertSetEqual({r.title for r in results},
+                            {'JavaScript: The Definitive Guide'})
+
+    def test_plain_text_invalid_operator(self):
+        with self.assertRaises(ValueError):
+            self.backend.search(PlainText('Guide', operator='xor'),
+                                models.Book.objects.all())
+
+        with self.assertRaises(ValueError):
+            self.backend.search('Guide', models.Book.objects.all(),
+                                operator='xor')
+
     def test_filter_equivalent(self):
         filter = Filter(Term('Javascript'))
         term = filter.child