Treat `Set` as an `Array` in `Relation#where`

I do not want to set the expectation that any enumerable object should
behave this way, but this case in particular comes up frequently enough
that I'm caving on this one.

Fixes #30684.

1 files changed, 13 insertions, 0 deletions

diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index ae1dc35bff..6270533dc2 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -1912,6 +1912,19 @@ class RelationTest < ActiveRecord::TestCase
     end
   end
 
+  test "#where with set" do
+    david = authors(:david)
+    mary = authors(:mary)
+
+    authors = Author.where(name: ["David", "Mary"].to_set)
+    assert_equal [david, mary], authors
+  end
+
+  test "#where with empty set" do
+    authors = Author.where(name: Set.new)
+    assert_empty authors
+  end
+
   private
     def custom_post_relation
       table_alias = Post.arel_table.alias("omg_posts")