[Fix rubocop#144] false positive for Rails/ReversibleMigration

change_table_comment is only irreversible when passing a string as
the comment. If we pass a hash with `:from` and `:to` keys, it
works as a reversible migration

Fixes rubocop#144

CHANGELOG.md

@@ -13,6 +13,8 @@
 * [#131](https://github.com/rubocop-hq/rubocop-rails/pull/131): Fix an incorrect autocorrect for `Rails/Presence` when using `[]` method. ([@forresty][])
 * [#142](https://github.com/rubocop-hq/rubocop-rails/pull/142): Fix an incorrect autocorrect for `Rails/EnumHash` when using nested constants. ([@koic][])
 * [#136](https://github.com/rubocop-hq/rubocop-rails/pull/136): Fix a false positive for `Rails/ReversibleMigration` when using `change_default` with `:from` and `:to` options. ([@sinsoku][])
+* [#144](https://github.com/rubocop-hq/rubocop-rails/issues/144): Fix a false positive for `Rails/ReversibleMigration` when using change_table_comment with a `:from` and `:to` hash. ([@DNA][])
+
 
 ## 2.3.2 (2019-09-01)
 
@@ -97,3 +99,4 @@
 [@forresty]: https://github.com/forresty
 [@sinsoku]: https://github.com/sinsoku
 [@pocke]: https://github.com/pocke
+[@DNA]: https://github.com/DNA

lib/rubocop/cop/rails/reversible_migration.rb

@@ -129,17 +129,13 @@ class ReversibleMigration < Cop
  MSG = '%<action>s is not reversible.'
 
  def_node_matcher :irreversible_schema_statement_call, <<-PATTERN
- (send nil? ${:change_table_comment :execute :remove_belongs_to} ...)
+ (send nil? ${:execute :remove_belongs_to} ...)
  PATTERN
 
  def_node_matcher :drop_table_call, <<-PATTERN
  (send nil? :drop_table ...)
  PATTERN
 
- def_node_matcher :change_column_default_call, <<-PATTERN
- (send nil? :change_column_default {[(sym _) (sym _)] (splat _)} $...)
- PATTERN
-
  def_node_matcher :remove_column_call, <<-PATTERN
  (send nil? :remove_column $...)
  PATTERN
@@ -158,7 +154,7 @@ def on_send(node)
 
  check_irreversible_schema_statement_node(node)
  check_drop_table_node(node)
- check_change_column_default_node(node)
+ check_reversible_hash_node(node)
  check_remove_column_node(node)
  check_remove_foreign_key_node(node)
  end
@@ -190,17 +186,15 @@ def check_drop_table_node(node)
  end
  end
 
- def check_change_column_default_node(node)
- change_column_default_call(node) do |args|
- unless all_hash_key?(args.last, :from, :to)
- add_offense(
- node,
- message: format(
- MSG, action: 'change_column_default(without :from and :to)'
- )
- )
- end
- end
+ def check_reversible_hash_node(node)
+ return if reversible_change_table_call?(node)
+
+ add_offense(
+ node,
+ message: format(
+ MSG, action: "#{node.method_name}(without :from and :to)"
+ )
+ )
  end
 
  def check_remove_column_node(node)
@@ -253,7 +247,8 @@ def reversible_change_table_call?(node)
  case node.method_name
  when :change, :remove
  false
- when :change_default
+ when :change_default, :change_column_default, :change_table_comment,
+ :change_column_comment
  all_hash_key?(node.arguments.last, :from, :to)
  else
  true

spec/rubocop/cop/rails/reversible_migration_spec.rb

@@ -126,6 +126,30 @@ def change
  RUBY
  end
 
+ context 'change_table_comment' do
+ it_behaves_like 'accepts',
+ 'change_table_comment(with :from and :to)', <<-RUBY
+ change_table_comment(:posts, from: nil, to: "draft")
+ RUBY
+
+ it_behaves_like 'offense',
+ 'change_table_comment(without :from and :to)', <<-RUBY
+ change_table_comment(:suppliers, 'new')
+ RUBY
+ end
+
+ context 'change_column_comment' do
+ it_behaves_like 'accepts',
+ 'change_column_comment(with :from and :to)', <<-RUBY
+ change_column_comment(:posts, :state, from: nil, to: "draft")
+ RUBY
+
+ it_behaves_like 'offense',
+ 'change_column_comment(without :from and :to)', <<-RUBY
+ change_column_comment(:suppliers, :qualification, 'new')
+ RUBY
+ end
+
  context 'remove_column' do
  it_behaves_like 'accepts', 'remove_column(with type)', <<-RUBY
  remove_column(:suppliers, :qualification, :string)