1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
|
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_index
# * add_timestamps
# * create_table
# * create_join_table
# * remove_timestamps
# * rename_column
# * rename_index
# * rename_table
class CommandRecorder
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 unless respond_to?(method, true)
send(method, args, &block)
end
def respond_to?(*args) # :nodoc:
super || delegate.respond_to?(*args)
end
[: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,
:change_column, :execute, :remove_columns, :change_column_null,
:add_foreign_key, :remove_foreign_key
# irreversible methods need to be here too
].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 = *args
unless options && options.is_a?(Hash) && 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]]
end
alias :invert_add_belongs_to :invert_add_reference
alias :invert_remove_belongs_to :invert_remove_reference
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
# Forwards any missing method call to the \target.
def method_missing(method, *args, &block)
if @delegate.respond_to?(method)
@delegate.send(method, *args, &block)
else
super
end
end
end
end
end
|