Backport to 4-2-stable "Let t.foreign_key use the same to_table twice"

activerecord/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Fix a bug where using `t.foreign_key` twice with the same `to_table` within
+    the same table definition would only create one foreign key.
+
+    *George Millo*
+
 *   Fix regression in dirty attribute tracking after #dup.  Changes to the
     clone no longer show as changed attributes in the original object.
 

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -99,7 +99,7 @@ class TableDefinition
       def initialize(types, name, temporary, options, as = nil)
         @columns_hash = {}
         @indexes = {}
-        @foreign_keys = {}
+        @foreign_keys = []
         @native = types
         @temporary = temporary
         @options = options
@@ -289,7 +289,7 @@ def index(column_name, options = {})
       end
 
       def foreign_key(table_name, options = {}) # :nodoc:
-        foreign_keys[table_name] = options
+        foreign_keys.push([table_name, options])
       end
 
       # Appends <tt>:datetime</tt> columns <tt>:created_at</tt> and

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -227,7 +227,7 @@ def create_table(table_name, options = {})
           end
         end
 
-        td.foreign_keys.each_pair do |other_table_name, foreign_key_options|
+        td.foreign_keys.each do |other_table_name, foreign_key_options|
           add_foreign_key(table_name, other_table_name, foreign_key_options)
         end
 

activerecord/test/cases/migration/references_foreign_key_test.rb

@@ -127,6 +127,22 @@ class ReferencesForeignKeyTest < ActiveRecord::TestCase
           @connection.drop_table "testing", if_exists: true
         end
       end
+
+      test "multiple foreign keys can be added to the same table" do
+        @connection.create_table :testings do |t|
+          t.integer :col_1
+          t.integer :col_2
+
+          t.foreign_key :testing_parents, column: :col_1
+          t.foreign_key :testing_parents, column: :col_2
+        end
+
+        fks = @connection.foreign_keys("testings").sort_by(&:column)
+
+        fk_definitions = fks.map {|fk| [fk.from_table, fk.to_table, fk.column] }
+        assert_equal([["testings", "testing_parents", "col_1"],
+                      ["testings", "testing_parents", "col_2"]], fk_definitions)
+      end
     end
   end
 end