# frozen_string_literal: true
module ActiveRecord
class Migration
# <tt>ActiveRecord::Migration::CommandRecorder</tt> records commands done during
# a migration and knows how to reverse those commands. The CommandRecorder
# knows how to invert the following commands:
#
# * add_column
# * add_foreign_key
# * add_index
# * add_reference
# * add_timestamps
# * change_column
# * change_column_default (must supply a :from and :to option)
# * change_column_null
# * create_join_table
# * create_table
# * disable_extension
# * drop_join_table
# * drop_table (must supply a block)
# * enable_extension
# * remove_column (must supply a type)
# * remove_columns (must specify at least one column name or more)
# * remove_foreign_key (must supply a second table)
# * remove_index
# * remove_reference
# * remove_timestamps
# * rename_column
# * rename_index
# * rename_table
class CommandRecorder
ReversibleAndIrreversibleMethods = [:create_table, :create_join_table, :rename_table, :add_column, :remove_column,
:rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps,
:change_column_default, :add_reference, :remove_reference, :transaction,
:drop_join_table, :drop_table, :execute_block, :enable_extension, :disable_extension,
:change_column, :execute, :remove_columns, :change_column_null,
:add_foreign_key, :remove_foreign_key
]
include JoinTable
attr_accessor :commands, :delegate, :reverting
def initialize(delegate = nil)
@commands = []
@delegate = delegate
@reverting = false
end
# While executing the given block, the recorded will be in reverting mode.
# All commands recorded will end up being recorded reverted
# and in reverse order.
# For example:
#
# recorder.revert{ recorder.record(:rename_table, [:old, :new]) }
# # same effect as recorder.record(:rename_table, [:new, :old])
def revert
@reverting = !@reverting
previous = @commands
@commands = []
yield
ensure
@commands = previous.concat(@commands.reverse)
@reverting = !@reverting
end
# Record +command+. +command+ should be a method name and arguments.
# For example:
#
# recorder.record(:method_name, [:arg1, :arg2])
def record(*command, &block)
if @reverting
@commands << inverse_of(*command, &block)
else
@commands << (command << block)
end
end
# Returns the inverse of the given command. For example:
#
# recorder.inverse_of(:rename_table, [:old, :new])
# # => [:rename_table, [:new, :old]]
#
# This method will raise an +IrreversibleMigration+ exception if it cannot
# invert the +command+.
def inverse_of(command, args, &block)
method = :"invert_#{command}"
raise IrreversibleMigration, <<-MSG.strip_heredoc unless respond_to?(method, true)
This migration uses #{command}, which is not automatically reversible.
To make the migration reversible you can either:
1. Define #up and #down methods in place of the #change method.
2. Use the #reversible method to define reversible behavior.
MSG
send(method, args, &block)
end
ReversibleAndIrreversibleMethods.each do |method|
class_eval <<-EOV, __FILE__, __LINE__ + 1
def #{method}(*args, &block) # def create_table(*args, &block)
record(:"#{method}", args, &block) # record(:create_table, args, &block)
end # end
EOV
end
alias :add_belongs_to :add_reference
alias :remove_belongs_to :remove_reference
def change_table(table_name, options = {}) # :nodoc:
yield delegate.update_table_definition(table_name, self)
end
private
module StraightReversions
private
{ transaction: :transaction,
execute_block: :execute_block,
create_table: :drop_table,
create_join_table: :drop_join_table,
add_column: :remove_column,
add_timestamps: :remove_timestamps,
add_reference: :remove_reference,
enable_extension: :disable_extension
}.each do |cmd, inv|
[[inv, cmd], [cmd, inv]].uniq.each do |method, inverse|
class_eval <<-EOV, __FILE__, __LINE__ + 1
def invert_#{method}(args, &block) # def invert_create_table(args, &block)
[:#{inverse}, args, block] # [:drop_table, args, block]
end # end
EOV
end
end
end
include StraightReversions
def invert_drop_table(args, &block)
if args.size == 1 && block == nil
raise ActiveRecord::IrreversibleMigration, "To avoid mistakes, drop_table is only reversible if given options or a block (can be empty)."
end
super
end
def invert_rename_table(args)
[:rename_table, args.reverse]
end
def invert_remove_column(args)
raise ActiveRecord::IrreversibleMigration, "remove_column is only reversible if given a type." if args.size <= 2
super
end
def invert_rename_index(args)
[:rename_index, [args.first] + args.last(2).reverse]
end
def invert_rename_column(args)
[:rename_column, [args.first] + args.last(2).reverse]
end
def invert_add_index(args)
table, columns, options = *args
options ||= {}
index_name = options[:name]
options_hash = index_name ? { name: index_name } : { column: columns }
[:remove_index, [table, options_hash]]
end
def invert_remove_index(args)
table, options_or_column = *args
if (options = options_or_column).is_a?(Hash)
unless options[:column]
raise ActiveRecord::IrreversibleMigration, "remove_index is only reversible if given a :column option."
end
options = options.dup
[:add_index, [table, options.delete(:column), options]]
elsif (column = options_or_column).present?
[:add_index, [table, column]]
end
end
alias :invert_add_belongs_to :invert_add_reference
alias :invert_remove_belongs_to :invert_remove_reference
def invert_change_column_default(args)
table, column, options = *args
unless options && options.is_a?(Hash) && options.has_key?(:from) && options.has_key?(:to)
raise ActiveRecord::IrreversibleMigration, "change_column_default is only reversible if given a :from and :to option."
end
[:change_column_default, [table, column, from: options[:to], to: options[:from]]]
end
def invert_change_column_null(args)
args[2] = !args[2]
[:change_column_null, args]
end
def invert_add_foreign_key(args)
from_table, to_table, add_options = args
add_options ||= {}
if add_options[:name]
options = { name: add_options[:name] }
elsif add_options[:column]
options = { column: add_options[:column] }
else
options = to_table
end
[:remove_foreign_key, [from_table, options]]
end
def invert_remove_foreign_key(args)
from_table, to_table, remove_options = args
raise ActiveRecord::IrreversibleMigration, "remove_foreign_key is only reversible if given a second table" if to_table.nil? || to_table.is_a?(Hash)
reversed_args = [from_table, to_table]
reversed_args << remove_options if remove_options
[:add_foreign_key, reversed_args]
end
def respond_to_missing?(method, _)
super || delegate.respond_to?(method)
end
# Forwards any missing method call to the \target.
def method_missing(method, *args, &block)
if delegate.respond_to?(method)
delegate.public_send(method, *args, &block)
else
super
end
end
end
end
end
