Ignore ENOENT when reading file annotations

Errno::ENOENT is occuring intermittently for some users.
This can happen even when the file seems to exist at the time.
Since we were already returning quietly if a file did not exist, just
try to read the file and rescue exceptions, returning silently.

Fixes #98

Author: martinemde

lib/code_ownership/private/ownership_mappers/file_annotations.rb

@@ -73,19 +73,20 @@ def update_cache(cache, files)
 
         sig { params(filename: String).returns(T.nilable(CodeTeams::Team)) }
         def file_annotation_based_owner(filename)
-          # If for a directory is named with an ownable extension, we need to skip
-          # so File.foreach doesn't blow up below. This was needed because Cypress
-          # screenshots are saved to a folder with the test suite filename.
-          return if File.directory?(filename)
-          return unless File.file?(filename)
-
           # The annotation should be on line 1 but as of this comment
           # there's no linter installed to enforce that. We therefore check the
           # first line (the Ruby VM makes a single `read(1)` call for 8KB),
           # and if the annotation isn't in the first two lines we assume it
           # doesn't exist.
 
-          line1 = File.foreach(filename).first
+          begin
+            line1 = File.foreach(filename).first
+          rescue Errno::EISDIR, Errno::ENOENT
+            # Ignore files that don't exist to avoid an intermittent (harmless?) bug.
+            # Ignoring directories is needed because Cypress
+            # screenshots are saved to a folder with the test suite filename.
+            return
+          end
 
           return if !line1
 

spec/lib/code_ownership/private/ownership_mappers/file_annotations_spec.rb

@@ -37,6 +37,28 @@ module CodeOwnership
     end
 
     describe '.for_file' do
+      context 'path is a directory' do
+        it 'returns nil' do
+          write_configuration
+          write_file('config/teams/bar.yml', <<~CONTENTS)
+            name: Bar
+          CONTENTS
+
+          expect(CodeOwnership.for_file('config/teams')).to be_nil
+        end
+      end
+
+      context 'path does not exist' do
+        it 'returns nil' do
+          write_configuration
+          write_file('config/teams/bar.yml', <<~CONTENTS)
+            name: Bar
+          CONTENTS
+
+          expect(CodeOwnership.for_file('config/teams/foo.yml')).to be_nil
+        end
+      end
+
       context 'ruby owned file' do
         before do
           write_configuration