1 files changed, 25 insertions, 8 deletions
diff --git a/actionpack/lib/action_dispatch/journey/formatter.rb b/actionpack/lib/action_dispatch/journey/formatter.rb
index 0323360faa..52396ec901 100644
--- a/actionpack/lib/action_dispatch/journey/formatter.rb
+++ b/actionpack/lib/action_dispatch/journey/formatter.rb
@@ -1,10 +1,13 @@
-require 'action_controller/metal/exceptions'
+# frozen_string_literal: true
+
+require "action_controller/metal/exceptions"
 
 module ActionDispatch
+  # :stopdoc:
   module Journey
     # The Formatter class is used for formatting URLs. For example, parameters
     # passed to +url_for+ in Rails will eventually call Formatter#generate.
-    class Formatter # :nodoc:
+    class Formatter
       attr_reader :routes
 
       def initialize(routes)
@@ -14,7 +17,7 @@ module ActionDispatch
 
       def generate(name, options, path_parameters, parameterize = nil)
         constraints = path_parameters.merge(options)
-        missing_keys = nil # need for variable scope
+        missing_keys = nil
 
         match_route(name, constraints) do |route|
           parameterized_parts = extract_parameterized_parts(route, options, path_parameters, parameterize)
@@ -32,15 +35,24 @@ module ActionDispatch
 
           defaults       = route.defaults
           required_parts = route.required_parts
-          parameterized_parts.keep_if do |key, value|
-            (defaults[key].nil? && value.present?) || value.to_s != defaults[key].to_s || required_parts.include?(key)
+
+          route.parts.reverse_each do |key|
+            break if defaults[key].nil? && parameterized_parts[key].present?
+            next if parameterized_parts[key].to_s != defaults[key].to_s
+            break if required_parts.include?(key)
+
+            parameterized_parts.delete(key)
           end
 
           return [route.format(parameterized_parts), params]
         end
 
-        message = "No route matches #{Hash[constraints.sort_by{|k,v| k.to_s}].inspect}"
-        message << " missing required keys: #{missing_keys.sort.inspect}" if missing_keys && !missing_keys.empty?
+        unmatched_keys = (missing_keys || []) & constraints.keys
+        missing_keys = (missing_keys || []) - unmatched_keys
+
+        message = +"No route matches #{Hash[constraints.sort_by { |k, v| k.to_s }].inspect}"
+        message << ", missing required keys: #{missing_keys.sort.inspect}" if missing_keys && !missing_keys.empty?
+        message << ", possible unmatched constraints: #{unmatched_keys.sort.inspect}" if unmatched_keys && !unmatched_keys.empty?
 
         raise ActionController::UrlGenerationError, message
       end
@@ -82,7 +94,11 @@ module ActionDispatch
           else
             routes = non_recursive(cache, options)
 
-            hash = routes.group_by { |_, r| r.score(options) }
+            supplied_keys = options.each_with_object({}) do |(k, v), h|
+              h[k.to_s] = true if v
+            end
+
+            hash = routes.group_by { |_, r| r.score(supplied_keys) }
 
             hash.keys.sort.reverse_each do |score|
               break if score < 0
@@ -169,4 +185,5 @@ module ActionDispatch
         end
     end
   end
+  # :startdoc:
 end