Allow to exclude methods from Metrics/MethodLength (#6286)

This makes it possible to exclude large methods about which it is known and such a dimension is permissible for them.

CHANGELOG.md

@@ -20,6 +20,7 @@
 
 ### Bug fixes
 
+* [#6286](https://github.com/rubocop-hq/rubocop/pull/6286): Allow exclusion of certain methods for `Metrics/MethodLength`. ([@akanoi][])
 * [#6267](https://github.com/rubocop-hq/rubocop/pull/6267): Fix undefined method 'method_name' for `Rails/FindEach`. ([@Knack][])
 * [#6278](https://github.com/rubocop-hq/rubocop/pull/6278): Fix false positive for `Naming/FileName` when investigating gemspecs. ([@kddeisz][])
 * [#6256](https://github.com/rubocop-hq/rubocop/pull/6256): Fix false positive for `Naming/FileName` when investigating dotfiles. ([@sinsoku][])
@@ -3585,6 +3586,7 @@
 [@schneems]: https://github.com/schneems
 [@ShockwaveNN]: https://github.com/ShockwaveNN
 [@Knack]: https://github.com/Knack
+[@akanoi]: https://github.com/akanoi
 [@yensaki]: https://github.com/yensaki
 [@ryanhageman]: https://github.com/ryanhageman
 [@autopp]: https://github.com/autopp

config/default.yml

@@ -1597,6 +1597,7 @@ Metrics/LineLength:
 Metrics/MethodLength:
   CountComments: false  # count full line comments?
   Max: 10
+  ExcludedMethods: []
 
 Metrics/ModuleLength:
   CountComments: false  # count full line comments?

lib/rubocop/cop/metrics/method_length.rb

@@ -12,6 +12,9 @@ class MethodLength < Cop
         LABEL = 'Method'.freeze
 
         def on_def(node)
+          excluded_methods = cop_config['ExcludedMethods']
+          return if excluded_methods.include?(String(node.method_name))
+
           check_code_length(node)
         end
         alias on_defs on_def

manual/cops_metrics.md

@@ -147,6 +147,7 @@ Name | Default value | Configurable values
 --- | --- | ---
 CountComments | `false` | Boolean
 Max | `10` | Integer
+ExcludedMethods | `[]` | Array
 
 ### References
 

spec/rubocop/config_loader_spec.rb

@@ -467,7 +467,8 @@ class FilePath < Cop
               'StyleGuide' => '#short-methods',
               'Enabled' => true,
               'CountComments' => false,
-              'Max' => 5
+              'Max' => 5,
+              'ExcludedMethods' => []
             }
           )
         expect do

spec/rubocop/cop/metrics/method_length_spec.rb

@@ -189,4 +189,35 @@ def m
       RUBY
     end
   end
+
+  context 'when method is defined in `ExcludedMethods`' do
+    before { cop_config['ExcludedMethods'] = ['foo'] }
+
+    it 'still rejects other methods with more than 5 lines' do
+      expect_offense(<<-RUBY.strip_indent)
+        def m 
+        ^^^^^^ Method has too many lines. [6/5]
+          a = 1
+          a = 2
+          a = 3
+          a = 4
+          a = 5
+          a = 6
+        end
+      RUBY
+    end
+
+    it 'accepts the foo method with more than 5 lines' do
+      expect_no_offenses(<<-RUBY.strip_indent)
+        def foo
+          a = 1
+          a = 2
+          a = 3
+          a = 4
+          a = 5
+          a = 6
+        end
+      RUBY
+    end
+  end
 end