[Fix rubocop#515] Fix an error for Rails/BulkChangeTable

Fixes rubocop#515
Follow up ruby/psych#487 and rails/rails@255b5ff

This PR fixes an error for `Rails/BulkChangeTable` when using Psych 4.0.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#515](https://github.com/rubocop/rubocop-rails/issues/515): Fix an error for `Rails/BulkChangeTable` when using Psych 4.0. ([@koic][])
+
 ## 2.11.1 (2021-06-25)
 
 ### Bug fixes

lib/rubocop/cop/rails/bulk_change_table.rb

@@ -194,7 +194,11 @@ def database_from_yaml
         def database_yaml
           return nil unless File.exist?('config/database.yml')
 
-          yaml = YAML.load_file('config/database.yml')
+          yaml = if YAML.respond_to?(:unsafe_load_file)
+                   YAML.unsafe_load_file('config/database.yml')
+                 else
+                   YAML.load_file('config/database.yml')
+                 end
           return nil unless yaml.is_a? Hash
 
           config = yaml['development']

spec/rubocop/cop/rails/bulk_change_table_spec.rb

@@ -414,12 +414,9 @@ def change
     let(:yaml) { nil }
 
     before do
-      allow(File).to receive(:exist?)
-        .with('config/database.yml')
-        .and_return(true)
-      allow(YAML).to receive(:load_file)
-        .with('config/database.yml')
-        .and_return(yaml)
+      allow(File).to receive(:exist?).with('config/database.yml').and_return(true)
+      allow(YAML).to receive(:load_file).with('config/database.yml').and_return(yaml)
+      allow(YAML).to receive(:unsafe_load_file).with('config/database.yml').and_return(yaml)
     end
 
     context 'mysql2' do