From 9c2de81c498ae637aeb78796e403dc2dd8fc2699 Mon Sep 17 00:00:00 2001
From: Aleh Kanoika <aleh.i.kanoika@gmail.com>
Date: Mon, 24 Sep 2018 08:15:11 +0300
Subject: [PATCH] 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                                  |  2 ++
 config/default.yml                            |  1 +
 lib/rubocop/cop/metrics/method_length.rb      |  3 ++
 manual/cops_metrics.md                        |  1 +
 spec/rubocop/config_loader_spec.rb            |  3 +-
 .../rubocop/cop/metrics/method_length_spec.rb | 31 +++++++++++++++++++
 6 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f8438c93ef..f0b01444cf9 100644
--- a/CHANGELOG.md
+++ b/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
diff --git a/config/default.yml b/config/default.yml
index 9a2b04290ad..be61caaa6a3 100644
--- a/config/default.yml
+++ b/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?
diff --git a/lib/rubocop/cop/metrics/method_length.rb b/lib/rubocop/cop/metrics/method_length.rb
index 39601bae353..fb65cdb3d73 100644
--- a/lib/rubocop/cop/metrics/method_length.rb
+++ b/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
diff --git a/manual/cops_metrics.md b/manual/cops_metrics.md
index 37e557f8631..7e269277f3f 100644
--- a/manual/cops_metrics.md
+++ b/manual/cops_metrics.md
@@ -147,6 +147,7 @@ Name | Default value | Configurable values
 --- | --- | ---
 CountComments | `false` | Boolean
 Max | `10` | Integer
+ExcludedMethods | `[]` | Array
 
 ### References
 
diff --git a/spec/rubocop/config_loader_spec.rb b/spec/rubocop/config_loader_spec.rb
index 1bd3e30cbf1..5b0d9e265b1 100644
--- a/spec/rubocop/config_loader_spec.rb
+++ b/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
diff --git a/spec/rubocop/cop/metrics/method_length_spec.rb b/spec/rubocop/cop/metrics/method_length_spec.rb
index 8cfb8c80751..03e24bc0d51 100644
--- a/spec/rubocop/cop/metrics/method_length_spec.rb
+++ b/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