Route constraints with an array do not allow building a path only parsing a path.

[urkle]

Steps to reproduce

# Given a route like this.
MyApplication::Application.routes.draw do
    get '/download/:platform' => 'download#platform',
        constraints: {
          platform: %w[windows linux macos],
        },
        as: :download_platform
end

Expected behavior

Routing test (rspec)

expect(get("/download/windows")).to route_to('download#platform',
                                                         platform: platform)

url building test (rspec)

def some_function(platform)
    download_platform_path(platform: platform)
end

expect(some_function('windows')).to eq(download_platform_path('windows'))

Actual behavior

The routing spec passes, but the url building test fails with a No route matches ... possible unmatched constraints: [:platform] error.

However,

If I change the constraint to this

MyApplication::Application.routes.draw do
    get '/download/:platform' => 'download#platform',
        constraints: {
          platform: /(windows|linux|macos)/,
        },
        as: :download_platform
end

both pass correctly.

System configuration

Rails version: 2.7.3

Ruby version: 6.0.5

[dorianmariecom]

I can reproduce with:

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", github: "rails/rails", branch: "main"
end

require "action_controller/railtie"

class DownloadController < ActionController::Base
  def platform
  end
end

class TestApp < Rails::Application
  routes.draw do
    get '/download/:platform' => 'download#platform',
      constraints: {
        platform: %w[windows linux macos],
      },
      as: :download_platform
  end
end

require "minitest/autorun"

class BugTest < Minitest::Test
  include Rails.application.routes.url_helpers

  def test_returns_success
    assert_equal "/download/windows", download_platform_path("windows")
  end
end

[dorianmariecom]

The constraints triggers the bug

[dorianmariecom]

Here is a patch with the a failing test on rails/rails:

diff --git a/actionpack/test/dispatch/routing/custom_url_helpers_test.rb b/actionpack/test/dispatch/routing/custom_url_helpers_test.rb
index a1a1e79884..56cb2ec2ab 100644
--- a/actionpack/test/dispatch/routing/custom_url_helpers_test.rb
+++ b/actionpack/test/dispatch/routing/custom_url_helpers_test.rb
@@ -85,6 +85,11 @@ class ProductPage < Page; end
     get "/profile", to: "users#profile", as: :profile
     get "/media/:id", to: "media#show", as: :media
     get "/pages/:id", to: "pages#show", as: :page
+    get(
+      "/download/:platform" => "download#platform",
+      constraints: { platform: %w[windows linux macos] },
+      as: :download
+    )
 
     resources :categories, :collections, :products, :manufacturers
 
@@ -145,6 +150,10 @@ def params
     ActionController::Parameters.new(page: 2, size: 25)
   end
 
+  def test_constraints_path
+    assert_equal "/download/macos", download_path(platform: :macos)
+  end
+
   def test_direct_paths
     assert_equal "/", website_path
     assert_equal "/", Routes.url_helpers.website_path

[dorianmariecom]

It looks like array constraints aren't supported and that your array is being converted to a regexp

route.path.requirements_for_missing_keys_check
# => {:platform=>/\A["windows", "linux", "macos"]\Z/}

[dorianmariecom]

Ok, got a patch, gonna submit a pull request:

diff --git a/actionpack/lib/action_dispatch/journey/formatter.rb b/actionpack/lib/action_dispatch/journey/formatter.rb
index 61d6d5c184..cf2ca9d7d3 100644
--- a/actionpack/lib/action_dispatch/journey/formatter.rb
+++ b/actionpack/lib/action_dispatch/journey/formatter.rb
@@ -175,6 +175,11 @@ def missing_keys(route, parts)
                 missing_keys ||= []
                 missing_keys << key
               end
+            when Array
+              unless tests[key].any? { |value| value.match?(parts[key]) }
+                missing_keys ||= []
+                missing_keys << key
+              end
             else
               unless tests[key].match?(parts[key])
                 missing_keys ||= []
diff --git a/actionpack/lib/action_dispatch/journey/path/pattern.rb b/actionpack/lib/action_dispatch/journey/path/pattern.rb
index d156adc108..29253e4211 100644
--- a/actionpack/lib/action_dispatch/journey/path/pattern.rb
+++ b/actionpack/lib/action_dispatch/journey/path/pattern.rb
@@ -172,8 +172,14 @@ def to_regexp
         end
 
         def requirements_for_missing_keys_check
-          @requirements_for_missing_keys_check ||= requirements.transform_values do |regex|
-            /\A#{regex}\Z/
+          @requirements_for_missing_keys_check ||= requirements.transform_values do |object|
+            if object.is_a?(Array)
+              object.map do |element|
+                /\A#{element}\Z/
+              end
+            else
+              /\A#{object}\Z/
+            end
           end
         end

[javierav]

It looks like array constraints aren't supported and that your array is being converted to a regexp

route.path.requirements_for_missing_keys_check
# => {:platform=>/\A["windows", "linux", "macos"]\Z/}

I also have the same issue. The documentation is clear, but not works:

https://api.rubyonrails.org/classes/ActionDispatch/Routing/Mapper/Base.html#method-i-match

:constraints
Constrains parameters with a hash of regular expressions or an object that responds to matches?. In addition, constraints other than path can also be specified with any object that responds to === (e.g. String, Array, Range, etc.).