Strong type Dependabot::Config::FileFetcher

common/lib/dependabot/config/file_fetcher.rb

@@ -1,30 +1,37 @@
-# typed: true
+# typed: strong
 # frozen_string_literal: true
 
+require "sorbet-runtime"
 require "dependabot/file_fetchers/base"
 require "dependabot/config/file"
 
 module Dependabot
   module Config
     class FileFetcher < FileFetchers::Base
-      CONFIG_FILE_PATHS = %w(.github/dependabot.yml .github/dependabot.yaml).freeze
+      extend T::Sig
 
+      CONFIG_FILE_PATHS = T.let(%w(.github/dependabot.yml .github/dependabot.yaml).freeze, T::Array[String])
+
+      sig { override.params(filenames: T::Array[String]).returns(T::Boolean) }
       def self.required_files_in?(filenames)
         CONFIG_FILE_PATHS.any? { |file| filenames.include?(file) }
       end
 
+      sig { override.returns(String) }
       def self.required_files_message
         "Repo must contain either a #{CONFIG_FILE_PATHS.join(' or a ')} file"
       end
 
+      sig { returns(T.nilable(Dependabot::DependencyFile)) }
       def config_file
-        @config_file ||= files.first
+        @config_file ||= T.let(files.first, T.nilable(Dependabot::DependencyFile))
       end
 
       private
 
+      sig { override.returns(T::Array[Dependabot::DependencyFile]) }
       def fetch_files
-        fetched_files = []
+        fetched_files = T.let([], T::Array[Dependabot::DependencyFile])
 
         CONFIG_FILE_PATHS.each do |file|
           fn = Pathname.new("/#{file}").relative_path_from(directory)