Fixed #28330 -- Prevented passing positional arguments to an Index.

Thanks Tim Graham for the review.

django/contrib/postgres/indexes.py

@@ -11,11 +11,11 @@ class BrinIndex(Index):
     # applicable.
     max_name_length = 31
 
-    def __init__(self, fields=[], name=None, pages_per_range=None):
+    def __init__(self, *, pages_per_range=None, **kwargs):
         if pages_per_range is not None and pages_per_range <= 0:
             raise ValueError('pages_per_range must be None or a positive integer')
         self.pages_per_range = pages_per_range
-        super().__init__(fields, name)
+        super().__init__(**kwargs)
 
     def deconstruct(self):
         path, args, kwargs = super().deconstruct()
@@ -33,10 +33,10 @@ class BrinIndex(Index):
 class GinIndex(Index):
     suffix = 'gin'
 
-    def __init__(self, fields=[], name=None, fastupdate=None, gin_pending_list_limit=None):
+    def __init__(self, *, fastupdate=None, gin_pending_list_limit=None, **kwargs):
         self.fastupdate = fastupdate
         self.gin_pending_list_limit = gin_pending_list_limit
-        super().__init__(fields, name)
+        super().__init__(**kwargs)
 
     def deconstruct(self):
         path, args, kwargs = super().deconstruct()

django/db/models/indexes.py

@@ -11,7 +11,7 @@ class Index:
     # cross-database compatibility with Oracle)
     max_name_length = 30
 
-    def __init__(self, fields=[], name=None):
+    def __init__(self, *, fields=[], name=None):
         if not isinstance(fields, list):
             raise ValueError('Index.fields must be a list.')
         if not fields:

docs/ref/contrib/postgres/indexes.txt

@@ -12,7 +12,7 @@ available from the ``django.contrib.postgres.indexes`` module.
 ``BrinIndex``
 =============
 
-.. class:: BrinIndex(fields=[], name=None, pages_per_range=None)
+.. class:: BrinIndex(pages_per_range=None, **options)
 
     Creates a `BRIN index
     <https://www.postgresql.org/docs/current/static/brin-intro.html>`_.
@@ -22,7 +22,7 @@ available from the ``django.contrib.postgres.indexes`` module.
 ``GinIndex``
 ============
 
-.. class:: GinIndex(fields=[], name=None, fastupdate=None, gin_pending_list_limit=None)
+.. class:: GinIndex(fastupdate=None, gin_pending_list_limit=None, **options)
 
     Creates a `gin index
     <https://www.postgresql.org/docs/current/static/gin.html>`_.

docs/releases/2.0.txt

@@ -404,6 +404,17 @@ For custom management commands that use options not created using
     class MyCommand(BaseCommand):
         stealth_options = ('option_name', ...)
 
+Indexes no longer accept positional arguments
+---------------------------------------------
+
+For example::
+
+    models.Index(['headline', '-pub_date'], 'index_name')
+
+raises an exception and should be replaced with::
+
+    models.Index(fields=['headline', '-pub_date'], name='index_name')
+
 Miscellaneous
 -------------