maven: stop querying repositories once one returns a result

maven/lib/dependabot/maven/update_checker/version_finder.rb

@@ -57,8 +57,10 @@ def versions
           version_details =
             repositories.map do |repository_details|
               url = repository_details.fetch("url")
-              dependency_metadata(repository_details).
-                css("versions > version").
+              xml = dependency_metadata(repository_details)
+              next [] unless xml
+
+              break xml.css("versions > version").
                 select { |node| version_class.correct?(node.content) }.
                 map { |node| version_class.new(node.content) }.
                 map { |version| { version: version, source_url: url } }
@@ -166,15 +168,16 @@ def fetch_dependency_metadata(repository_details)
             headers: repository_details.fetch("auth_headers")
           )
           check_response(response, repository_details.fetch("url"))
+          return unless response.status < 400
 
           Nokogiri::XML(response.body)
         rescue URI::InvalidURIError
-          Nokogiri::XML("")
+          nil
         rescue Excon::Error::Socket, Excon::Error::Timeout,
                Excon::Error::TooManyRedirects
           raise if central_repo_urls.include?(repository_details["url"])
 
-          Nokogiri::XML("")
+          nil
         end
 
         def check_response(response, repository_url)

maven/lib/dependabot/maven/version.rb

@@ -43,6 +43,10 @@ def initialize(version)
         super(version.to_s.tr("_", "-"))
       end
 
+      def inspect
+        "#<#{self.class} #{@version_string}>"
+      end
+
       def to_s
         @version_string
       end

maven/spec/dependabot/maven/update_checker/version_finder_spec.rb

@@ -707,9 +707,12 @@
             fixture("maven_central_metadata", "with_date_releases.xml")
           stub_request(:get, maven_central_metadata_url).
             to_return(status: 200, body: body)
+          # 404 causes Dependabot to fall back to the central repo
+          stub_request(:get, jboss_metadata_url).
+            to_return(status: 404)
         end
 
-        its(:count) { is_expected.to eq(87) }
+        its(:count) { is_expected.to eq(17) }
 
         describe "the first version" do
           subject { versions.first }