Clarify binding naming convention in error message

Author: svkrieger

lib/cloud_controller/diego/service_binding_files_builder.rb

@@ -24,7 +24,7 @@ def build
         @service_bindings.select(&:create_succeeded?).each do |service_binding|
           sb_hash = ServiceBindingPresenter.new(service_binding, include_instance: true).to_hash
           name = sb_hash[:name]
-          raise IncompatibleBindings.new("Invalid binding name: #{name}") unless valid_name?(name)
+          raise IncompatibleBindings.new("Invalid binding name: '#{name}'. Name must match #{binding_naming_convention.inspect}") unless valid_name?(name)
           raise IncompatibleBindings.new("Duplicate binding name: #{name}") if names.add?(name).nil?
 
           # add the credentials first
@@ -47,6 +47,10 @@ def build
 
       private
 
+      def binding_naming_convention
+        /^[a-z0-9\-.]{1,253}$/
+      end
+
       # - adds a Diego::Bbs::Models::File object to the service_binding_files hash
       # - binding name is used as the directory name, key is used as the file name
       # - returns the bytesize of the path and content
@@ -71,7 +75,7 @@ def add_file(service_binding_files, name, key, value)
       end
 
       def valid_name?(name)
-        name.match?(/^[a-z0-9\-.]{1,253}$/)
+        name.match?(binding_naming_convention)
       end
 
       def transform_vcap_services_attribute(name)

spec/unit/lib/cloud_controller/diego/service_binding_files_builder_spec.rb

@@ -239,7 +239,7 @@ module VCAP::CloudController::Diego
           let(:binding_name) { 'binding_name' }
 
           it 'raises an exception' do
-            expect { service_binding_files }.to raise_error(ServiceBindingFilesBuilder::IncompatibleBindings, 'Invalid binding name: binding_name')
+            expect { service_binding_files }.to raise_error(ServiceBindingFilesBuilder::IncompatibleBindings, "Invalid binding name: 'binding_name'. Name must match /^[a-z0-9\\-.]{1,253}$/")
           end
         end