Add validation to ensure GitHub teams are unique (#62)

* Add a vaildation for unique github teams

* bump version

* fix readme typo

Author: Alex Evanczuk

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    code_ownership (1.32.14)
+    code_ownership (1.32.15)
       code_teams (~> 1.0)
       packs
       sorbet-runtime

README.md

@@ -125,7 +125,7 @@ CodeOwnership comes with a validation function to ensure the following things ar
 1) Only one mechanism is defining file ownership. That is -- you can't have a file annotation on a file owned via package-based or glob-based ownership. This helps make ownership behavior more clear by avoiding concerns about precedence.
 2) All teams referenced as an owner for any file or package is a valid team (i.e. it's in the list of `CodeTeams.all`).
 3) All files have ownership. You can specify in `unowned_globs` to represent a TODO list of files to add ownership to.
-3) The `.github/CODEOWNERS` file is up to date. This is automatically corrected and staged unless specified otherwise with `bin/codeownership validate --skip-autocorrect --skip-stage`. You can turn this validation off by setting `skip_codeowners_validation: true` in `code_ownership.yml`.
+3) The `.github/CODEOWNERS` file is up to date. This is automatically corrected and staged unless specified otherwise with `bin/codeownership validate --skip-autocorrect --skip-stage`. You can turn this validation off by setting `skip_codeowners_validation: true` in `config/code_ownership.yml`.
 
 CodeOwnership also allows you to specify which globs and file extensions should be considered ownable.
 

code_ownership.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = 'code_ownership'
-  spec.version       = '1.32.14'
+  spec.version       = '1.32.15'
   spec.authors       = ['Gusto Engineers']
   spec.email         = ['dev@gusto.com']
   spec.summary       = 'A gem to help engineering teams declare ownership of code'

lib/code_ownership/private/team_plugins/github.rb

@@ -18,6 +18,28 @@ def github
             raw_github['do_not_add_to_codeowners_file'] || false
           )
         end
+
+        sig { override.params(teams: T::Array[CodeTeams::Team]).returns(T::Array[String]) }
+        def self.validation_errors(teams)
+          all_github_teams = teams.flat_map { |team| self.for(team).github.team }
+
+          teams_used_more_than_once = all_github_teams.tally.select do |_team, count|
+            count > 1
+          end
+
+          errors = T.let([], T::Array[String])
+
+          if teams_used_more_than_once.any?
+            errors << <<~ERROR
+              The following teams are specified multiple times:
+              Each code team must have a unique GitHub team in order to write the CODEOWNERS file correctly.
+
+              #{teams_used_more_than_once.keys.join("\n")}
+            ERROR
+          end
+
+          errors
+        end
       end
     end
   end

spec/lib/code_ownership/private/validations/github_codeowners_up_to_date_spec.rb

@@ -592,5 +592,28 @@ module CodeOwnership
         end
       end
     end
+
+    describe 'uniqueness of github teams' do
+      before do
+        write_file('config/teams/bar.yml', <<~CONTENTS)
+          name: Bar
+          github:
+            team: '@MyOrg/bar-team'
+        CONTENTS
+
+        write_file('config/teams/foo.yml', <<~CONTENTS)
+          name: Bar
+          github:
+            team: '@MyOrg/bar-team'
+        CONTENTS
+      end
+
+      it 'expect code teams validations to fail' do
+        expect(CodeTeams.validation_errors(CodeTeams.all)).to eq([
+          "More than 1 definition for Bar found",
+          "The following teams are specified multiple times:\nEach code team must have a unique GitHub team in order to write the CODEOWNERS file correctly.\n\n@MyOrg/bar-team\n"
+        ])
+      end
+    end
   end
 end