[5.1.x] Fixed #35665 -- Fixed a crash when passing an empty order_by to Window.

This also caused un-ordered sliced prefetches to crash as they rely on Window.

Regression in e16d0c176e9b89628cdec5e58c418378c4a2436a that made OrderByList
piggy-back ExpressionList without porting the empty handling that the latter
provided.

Supporting explicit empty ordering on Window functions and slicing is arguably
a foot-gun design due to how backends will return undeterministic results but
this is a problem that requires a larger discussion.

Refs #35064.

Thanks Andrew Backer for the report and Mariusz for the review.

Backport of 602fe961e6834d665f2359087a1272e9f9806b71 from main.

2 files changed, 6 insertions, 7 deletions

diff --git a/django/db/backends/oracle/features.py b/django/db/backends/oracle/features.py
index a83560b892..72c6180f50 100644
--- a/django/db/backends/oracle/features.py
+++ b/django/db/backends/oracle/features.py
@@ -116,6 +116,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "Oracle requires ORDER BY in row_number, ANSI:SQL doesn't.": {
                 "expressions_window.tests.WindowFunctionTests."
                 "test_row_number_no_ordering",
+                "prefetch_related.tests.PrefetchLimitTests.test_empty_order",
             },
             "Oracle doesn't support changing collations on indexed columns (#33671).": {
                 "migrations.test_operations.OperationTests."
diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py
index 0f5e68b0d4..c24c585658 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -1377,16 +1377,14 @@ class ExpressionList(Func):
 
     template = "%(expressions)s"
 
-    def __init__(self, *expressions, **extra):
-        if not expressions:
-            raise ValueError(
-                "%s requires at least one expression." % self.__class__.__name__
-            )
-        super().__init__(*expressions, **extra)
-
     def __str__(self):
         return self.arg_joiner.join(str(arg) for arg in self.source_expressions)
 
+    def as_sql(self, *args, **kwargs):
+        if not self.source_expressions:
+            return "", ()
+        return super().as_sql(*args, **kwargs)
+
     def as_sqlite(self, compiler, connection, **extra_context):
         # Casting to numeric is unnecessary.
         return self.as_sql(compiler, connection, **extra_context)