Fix bug when file annotation is removed (#63)

* Add failing test

* fix failing test

* bump version

Author: Alex Evanczuk

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    code_ownership (1.32.15)
+    code_ownership (1.32.16)
       code_teams (~> 1.0)
       packs
       sorbet-runtime

code_ownership.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = 'code_ownership'
-  spec.version       = '1.32.15'
+  spec.version       = '1.32.16'
   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/ownership_mappers/file_annotations.rb

@@ -47,10 +47,19 @@ def globs_to_owner(files)
           override.params(cache: GlobsToOwningTeamMap, files: T::Array[String]).returns(GlobsToOwningTeamMap)
         end
         def update_cache(cache, files)
-          cache.merge!(globs_to_owner(files))
+          # We map files to nil owners so that files whose annotation have been removed will be properly
+          # overwritten (i.e. removed) from the cache.
+          updated_cache_for_files = globs_to_owner(files)
+          cache.merge!(updated_cache_for_files)
+
           invalid_files = cache.keys.select do |file|
-            !Private.file_tracked?(file)
+            # If a file is not tracked, it should be removed from the cache
+            !Private.file_tracked?(file) ||
+            # If a file no longer has a file annotation (i.e. `globs_to_owner` doesn't map it)
+            # it should be removed from the cache
+            !updated_cache_for_files.key?(file)
           end
+
           invalid_files.each do |invalid_file|
             cache.delete(invalid_file)
           end

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

@@ -577,6 +577,58 @@ module CodeOwnership
             end
           end
         end
+
+        context 'in an application with a CODEOWNERS file that has a reference to a file that has had an annotation removed' do
+          before do
+            write_configuration
+
+            write_file('packs/my_pack/had_annotation_file.rb', <<~CONTENTS)
+            CONTENTS
+
+            write_file('config/teams/bar.yml', <<~CONTENTS)
+              name: Bar
+              github:
+                team: '@MyOrg/bar-team'
+            CONTENTS
+          end
+
+          it 'prints out the diff' do
+            FileUtils.mkdir('.github')
+            codeowners_path.write <<~CODEOWNERS
+              # STOP! - DO NOT EDIT THIS FILE MANUALLY
+              # This file was automatically generated by "bin/codeownership validate".
+              #
+              # CODEOWNERS is used for GitHub to suggest code/file owners to various GitHub
+              # teams. This is useful when developers create Pull Requests since the
+              # code/file owner is notified. Reference GitHub docs for more details:
+              # https://help.github.com/en/articles/about-code-owners
+
+              # Annotations at the top of file
+              /packs/my_pack/had_annotation_file.rb @MyOrg/bar-team
+
+              # Team YML ownership
+              /config/teams/bar.yml @MyOrg/bar-team
+            CODEOWNERS
+
+            expect_any_instance_of(codeowners_validation).to_not receive(:`) # rubocop:disable RSpec/AnyInstance
+            expect { CodeOwnership.validate!(autocorrect: false) }.to raise_error do |e|
+              expect(e).to be_a CodeOwnership::InvalidCodeOwnershipConfigurationError
+              expect(e.message).to eq <<~EXPECTED.chomp
+                Some files are missing ownership:
+
+                - packs/my_pack/had_annotation_file.rb
+
+                CODEOWNERS out of date. Run `bin/codeownership validate` to update the CODEOWNERS file
+
+                CODEOWNERS should not contain the following lines, but it does:
+                - "# Annotations at the top of file"
+                - "/packs/my_pack/had_annotation_file.rb @MyOrg/bar-team"
+
+                See https://github.com/rubyatscale/code_ownership#README.md for more details
+              EXPECTED
+            end
+          end
+        end
       end
 
       context 'code_ownership.yml has skip_codeowners_validation set' do