Add `foreign_key` as an option to `references` for `change_table`

This has the same comments as 9af90ffa00ba35bdee888e3e1ab775ba0bdbe72c,
however it affects the `add_reference` method, and `t.references` in the
context of a `change_table` block.

There is a lot of duplication of code between creating and updating
tables. We should re-evaluate the structure of this code from a high
level so changes like this don't need to be made in two places. (Note to
self)

1 files changed, 43 insertions, 0 deletions

diff --git a/activerecord/test/cases/migration/references_foreign_key_test.rb b/activerecord/test/cases/migration/references_foreign_key_test.rb
index 2fa7584a60..c6f0d50a8d 100644
--- a/activerecord/test/cases/migration/references_foreign_key_test.rb
+++ b/activerecord/test/cases/migration/references_foreign_key_test.rb
@@ -54,6 +54,49 @@ module ActiveRecord
           end
         end
       end
+
+      test "foreign keys can be created while changing the table" do
+        @connection.create_table :testings
+        @connection.change_table :testings do |t|
+          t.references :testing_parent, foreign_key: true
+        end
+
+        fk = @connection.foreign_keys("testings").first
+        assert_equal "testings", fk.from_table
+        assert_equal "testing_parents", fk.to_table
+      end
+
+      test "foreign keys are not added by default when changing the table" do
+        @connection.create_table :testings
+        @connection.change_table :testings do |t|
+          t.references :testing_parent
+        end
+
+        assert_equal [], @connection.foreign_keys("testings")
+      end
+
+      test "foreign keys accept options when changing the table" do
+        @connection.change_table :testing_parents do |t|
+          t.integer :other_id
+          t.index :other_id, unique: true
+        end
+        @connection.create_table :testings
+        @connection.change_table :testings do |t|
+          t.references :testing_parent, foreign_key: { primary_key: :other_id }
+        end
+
+        fk = @connection.foreign_keys("testings").find { |k| k.to_table == "testing_parents" }
+        assert_equal "other_id", fk.primary_key
+      end
+
+      test "foreign keys cannot be added to polymorphic relations when changing the table" do
+        @connection.create_table :testings
+        @connection.change_table :testings do |t|
+          assert_raises(ArgumentError) do
+            t.references :testing_parent, polymorphic: true, foreign_key: true
+          end
+        end
+      end
     end
   end
 end