[Fix rubocop#2722] ExtraSpacing doesn't align optarg equals with assi…

…gnment equals

CHANGELOG.md

@@ -13,6 +13,7 @@
 
 ### Bug fixes
 
+* [#2722](https://github.com/bbatsov/rubocop/issues/2722): `Style/ExtraSpacing` does not attempt to align an equals sign in an argument list with one in an assignment statement. ([@alexdowad][])
 * [#3133](https://github.com/bbatsov/rubocop/issues/3133): `Style/MultilineMethodCallBraceLayout` does not register offenses for single-line calls. ([@alexdowad][])
 * [#3170](https://github.com/bbatsov/rubocop/issues/3170): `Style/MutableConstant` does not infinite-loop when correcting an array with no brackets. ([@alexdowad][])
 * [#3150](https://github.com/bbatsov/rubocop/issues/3150): Fix auto-correct for Style/MultilineArrayBraceLayout. ([@jspanjers][])

lib/rubocop/cop/style/extra_spacing.rb

@@ -27,8 +27,15 @@ class ExtraSpacing < Cop
         MSG_UNALIGNED_ASGN = '`=` is not aligned with the %s assignment.'.freeze
 
         def investigate(processed_source)
+          return if processed_source.ast.nil?
+
           if force_equal_sign_alignment?
             @asgn_tokens = processed_source.tokens.select { |t| equal_sign?(t) }
+            # we don't want to operate on equals signs which are part of an
+            #   optarg in a method definition
+            # e.g.: def method(optarg = default_val); end
+            @asgn_tokens = remove_optarg_equals(@asgn_tokens, processed_source)
+
             # Only attempt to align the first = on each line
             @asgn_tokens = Set.new(@asgn_tokens.uniq { |t| t.pos.line })
             @asgn_lines  = @asgn_tokens.map { |t| t.pos.line }
@@ -205,6 +212,12 @@ def align_column(asgn_token)
           spaces  = leading.size - (leading =~ / *\Z/)
           asgn_token.pos.last_column - spaces + 1
         end
+
+        def remove_optarg_equals(asgn_tokens, processed_source)
+          optargs    = processed_source.ast.each_node(:optarg)
+          optarg_eql = optargs.map { |o| o.loc.operator.begin_pos }.to_set
+          asgn_tokens.reject { |t| optarg_eql.include?(t.pos.begin_pos) }
+        end
       end
     end
   end

spec/rubocop/cop/style/extra_spacing_spec.rb

@@ -329,5 +329,13 @@
                                 'a.attribute_name = 2',
                                 'abc[1]           = 3'].join("\n"))
     end
+
+    it 'does not register an offense when optarg equals is not aligned with ' \
+       'assignment equals sign' do
+      inspect_source(cop, ['def method(arg = 1)',
+                           '  var = arg',
+                           'end'])
+      expect(cop.offenses).to be_empty
+    end
   end
 end