[Fix rubocop#7814] Fix a false positive for Migrate/DepartmentName cop

### Summary

Fixes rubocop#7814.

This PR fixes a false positive for `Migrate/DepartmentName` cop
when inspecting an unexpected disable comment format.

e.g. `# rubocop:disable Style:BlockComments`

The above expected format is `# rubocop:disable Style/BlockComments`.

### Other Information

`Migration/DepartmentName` cop's role is to complement a department name.
The role would be simple if another feature could detect unexpected
disable comment format.

CHANGELOG.md

@@ -44,6 +44,7 @@
 * [#7682](https://github.com/rubocop-hq/rubocop/issues/7682): Fix `Style/InverseMethods` autofix leaving parenthesis. ([@tejasbubane][])
 * [#7745](https://github.com/rubocop-hq/rubocop/issues/7745): Suppress a pending cop warnings when pending cop's department is disabled. ([@koic][])
 * [#7759](https://github.com/rubocop-hq/rubocop/issues/7759): Fix an error for `Layout/LineLength` cop when using lambda syntax that argument is not enclosed in parentheses. ([@koic][])
+* [#7814](https://github.com/rubocop-hq/rubocop/issues/7814): Fix a false positive for `Migrate/DepartmentName` cop when inspecting an unexpected disabled comment format. ([@koic][])
 
 ### Changes
 

lib/rubocop/cop/migration/department_name.rb

@@ -14,19 +14,24 @@ class DepartmentName < Cop
           /\A(# *rubocop *: *((dis|en)able|todo) +)(.*)/.freeze
 
         # The token that makes up a disable comment.
-        # The token used after `# rubocop: disable` are `A-z`, `/`, and `,`.
-        # Also `A-z` includes `all`.
-        DISABLING_COPS_CONTENT_TOKEN = %r{[A-z/,]+}.freeze
+        # The allowed specification for comments after `# rubocop: disable` is
+        # `DepartmentName/CopName` or` all`.
+        DISABLING_COPS_CONTENT_TOKEN = %r{[A-z]+/[A-z]+|all}.freeze
 
         def investigate(processed_source)
           processed_source.each_comment do |comment|
             next if comment.text !~ DISABLE_COMMENT_FORMAT
 
             offset = Regexp.last_match(1).length
-            Regexp.last_match(4).scan(%r{[\w/]+|\W+}) do |name|
-              break unless valid_content_token?(name.strip)
 
-              check_cop_name(name, comment, offset)
+            Regexp.last_match(4).scan(/[^,]+|[\W]+/) do |name|
+              trimmed_name = name.strip
+
+              break if contain_plain_comment?(trimmed_name)
+
+              unless valid_content_token?(trimmed_name)
+                check_cop_name(trimmed_name, comment, offset)
+              end
 
               offset += name.length
             end
@@ -47,16 +52,24 @@ def autocorrect(range)
 
         private
 
-        def check_cop_name(name, comment, offset)
-          return if name !~ /^[A-Z]/ || name =~ %r{/}
+        def disable_comment_offset
+          Regexp.last_match(1).length
+        end
 
+        def check_cop_name(name, comment, offset)
           start = comment.location.expression.begin_pos + offset
           range = range_between(start, start + name.length)
+
           add_offense(range, location: range)
         end
 
         def valid_content_token?(content_token)
-          !DISABLING_COPS_CONTENT_TOKEN.match(content_token).nil?
+          !/\W+/.match(content_token).nil? ||
+            !DISABLING_COPS_CONTENT_TOKEN.match(content_token).nil?
+        end
+
+        def contain_plain_comment?(name)
+          name == '#'
         end
 
         def qualified_legacy_cop_name(cop_name)

spec/rubocop/cop/migration/department_name_spec.rb

@@ -89,4 +89,16 @@
       RUBY
     end
   end
+
+  # `Migration/DepartmentName` cop's role is to complement a department name.
+  # The role would be simple if another feature could detect unexpected
+  # disable comment format.
+  context 'when an unexpected disable comment format' do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        # rubocop:disable Style:Alias
+        alias :ala :bala
+      RUBY
+    end
+  end
 end