From a1a50474bb640fa49afada86cd0e5cc76aea4d0d Mon Sep 17 00:00:00 2001
From: Greg Rychlewski <greg.rychlewski@gmail.com>
Date: Tue, 8 Oct 2024 14:56:01 -0400
Subject: [PATCH] Raise when empty list is given to `values/2` (#4523)

---
 lib/ecto/query.ex                     | 4 ++++
 lib/ecto/query/api.ex                 | 3 ++-
 test/ecto/query/builder/from_test.exs | 8 ++++++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/ecto/query.ex b/lib/ecto/query.ex
index 4168c49d1c..5af3cd3f4c 100644
--- a/lib/ecto/query.ex
+++ b/lib/ecto/query.ex
@@ -485,6 +485,10 @@ defmodule Ecto.Query do
     @moduledoc false
     defstruct [:types, :num_rows, :params]
 
+    def new([], _types) do
+      raise ArgumentError, "must provide a non-empty list to values/2"
+    end
+
     def new(values_list, types) do
       fields = fields(values_list)
       types = types!(fields, types)
diff --git a/lib/ecto/query/api.ex b/lib/ecto/query/api.ex
index 0ce9f8bcea..9d2c6ce540 100644
--- a/lib/ecto/query/api.ex
+++ b/lib/ecto/query/api.ex
@@ -515,7 +515,8 @@ defmodule Ecto.Query.API do
   and `Ecto.Query.join/5`.
 
   The first argument is a list of maps representing the values of the constant table.
-  Each entry in the list must have exactly the same fields or an error is raised.
+  An error is raised if the list is empty or if every map does not have exactly the
+  same fields.
 
   The second argument is a map of types corresponding to the fields in the first argument.
   Each field must be given a type or an error is raised. Any type that can be specified in
diff --git a/test/ecto/query/builder/from_test.exs b/test/ecto/query/builder/from_test.exs
index b6f4eeac76..8114e587d9 100644
--- a/test/ecto/query/builder/from_test.exs
+++ b/test/ecto/query/builder/from_test.exs
@@ -27,6 +27,14 @@ defmodule Ecto.Query.Builder.FromTest do
     types_kw = Enum.map(types, & &1)
     assert query.from.source == {:values, [], [types_kw, length(values)]}
 
+    # Empty values
+    msg = "must provide a non-empty list to values/2"
+
+    assert_raise ArgumentError, msg, fn ->
+      from v in values([], %{})
+    end
+
+
     # Missing type
     msg = "values/2 must declare the type for every field. The type was not given for field `text`"