fk: support dependent option (:delete, :nullify and :restrict).

7 files changed, 83 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
index ad62eab4d2..57790d5667 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -19,11 +19,13 @@ module ActiveRecord
         end
 
         def visit_AddForeignKey(o)
-          <<-SQL
+          sql = <<-SQL
 ADD CONSTRAINT #{quote_column_name(o.name)}
 FOREIGN KEY (#{quote_column_name(o.column)})
   REFERENCES #{quote_table_name(o.to_table)} (#{quote_column_name(o.primary_key)})
           SQL
+          sql << " #{dependency_sql(o.dependent)}" if o.dependent
+          sql
         end
 
         def visit_DropForeignKey(name)
@@ -98,6 +100,15 @@ FOREIGN KEY (#{quote_column_name(o.column)})
           def options_include_default?(options)
             options.include?(:default) && !(options[:null] == false && options[:default].nil?)
           end
+
+          def dependency_sql(dependency)
+            case dependency
+              when :nullify then "ON DELETE SET NULL"
+              when :delete  then "ON DELETE CASCADE"
+              when :restrict then "ON DELETE RESTRICT"
+              else ""
+            end
+          end
       end
     end
   end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index c18ebf1014..66ebf82971 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -37,6 +37,10 @@ module ActiveRecord
       def primary_key
         options[:primary_key]
       end
+
+      def dependent
+        options[:dependent]
+      end
     end
 
     # Represents the schema of an SQL table in an abstract way. This class
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index db04ebc802..fe752126ad 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -652,7 +652,8 @@ module ActiveRecord
         options = {
           column: options.fetch(:column),
           primary_key: primary_key,
-          name: foreign_key_name(from_table, options)
+          name: foreign_key_name(from_table, options),
+          dependent: options.fetch(:dependent, nil)
         }
         at = create_alter_table from_table
         at.add_foreign_key to_table, options
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 6ba226765c..9610296043 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -524,7 +524,19 @@ module ActiveRecord
         create_table_info = select_one("SHOW CREATE TABLE #{quote_table_name(table_name)}")["Create Table"]
 
         fk_info.map do |row|
-          options = {column: row['column'], name: row['name'], primary_key: row['primary_key']}
+          options = {
+            column: row['column'],
+            name: row['name'],
+            primary_key: row['primary_key']
+          }
+
+          if create_table_info =~ /CONSTRAINT #{quote_column_name(row['name'])} FOREIGN KEY .* REFERENCES .* ON DELETE (CASCADE|SET NULL|RESTRICT)/
+            options[:dependent] = case $1
+              when 'CASCADE'  then :delete
+              when 'SET NULL' then :nullify
+              end
+          end
+
           ForeignKeyDefinition.new(table_name, row['to_table'], options)
         end
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index c061337e71..7b61ff81ba 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -467,7 +467,14 @@ ORDER BY c.conname
             options = {
               column: row['column'],
               name: row['name'],
-              primary_key: row['primary_key'] }
+              primary_key: row['primary_key']
+            }
+
+            options[:dependent] = case row['dependency']
+              when 'c'; :delete
+              when 'n'; :nullify
+              when 'r'; :restrict
+              end
             ForeignKeyDefinition.new(table_name, row["to_table"], options)
           end
         end
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 3db36458db..c415236c45 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -226,6 +226,8 @@ HEADER
                      'primary_key: ' + foreign_key.primary_key.inspect,
                      'name: ' + foreign_key.name.inspect
                     ]
+            parts << ('dependent: ' + foreign_key.dependent.inspect) if foreign_key.dependent
+
             '  ' + parts.join(', ')
           end
 
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index f299762b42..fbdb921334 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -77,6 +77,41 @@ module ActiveRecord
         end
       end
 
+      def test_add_dependent_restrict_foreign_key
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", dependent: :restrict
+
+        foreign_keys = @connection.foreign_keys("astronauts")
+        assert_equal 1, foreign_keys.size
+
+        fk = foreign_keys.first
+        if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
+          # ON DELETE RESTRICT is the default on MySQL
+          assert_equal nil, fk.dependent
+        else
+          assert_equal :restrict, fk.dependent
+        end
+      end
+
+      def test_add_dependent_delete_foreign_key
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", dependent: :delete
+
+        foreign_keys = @connection.foreign_keys("astronauts")
+        assert_equal 1, foreign_keys.size
+
+        fk = foreign_keys.first
+        assert_equal :delete, fk.dependent
+      end
+
+      def test_add_dependent_nullify_foreign_key
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", dependent: :nullify
+
+        foreign_keys = @connection.foreign_keys("astronauts")
+        assert_equal 1, foreign_keys.size
+
+        fk = foreign_keys.first
+        assert_equal :nullify, fk.dependent
+      end
+
       def test_remove_foreign_key
         @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id"
 
@@ -97,6 +132,13 @@ module ActiveRecord
         output = dump_table_schema "fk_test_has_fk"
         assert_match %r{\s+add_foreign_key "fk_test_has_fk", "fk_test_has_pk", column: "fk_id", primary_key: "id", name: "fk_name"$}, output
       end
+
+      def test_schema_dumping_dependent_option
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", dependent: :nullify
+
+        output = dump_table_schema "astronauts"
+        assert_match %r{\s+add_foreign_key "astronauts",.+dependent: :nullify$}, output
+      end
     end
   end
 end