Using Rails 5 (the API flag) and getting no route error despite route declared

Question

This is my controller:

class Api::V1::UsersController < ApplicationController
  respond_to :json

  def show
    respond_with User.find(params[:id])
  end
end

This is my routes.rb

require 'api_constraints'

Rails.application.routes.draw do
  devise_for :users
  # Api definition
  namespace :api, defaults: { format: :json }, constraints: { subdomain: 'api' }, path: '/' do
    scope module: :v1, constraints: ApiConstraints.new(version: 1, default: true) do
      resources :users, :only => [:show]
    end
  end
end

This is my lib/api_constraints.rb

class ApiConstraints
  def initialize(options)
    @version = options[:version]
    @default = options[:default]
  end

  def matches?(req)
    @default || req.headers['Accept'].include?("application/vnd.myapp.v#{@version}")
  end
end

I added a record to my DB as can be seen here:

[3] pry(main)> User.all
  User Load (0.4ms)  SELECT "users".* FROM "users"
=> [#<User:0x007fbdb31079f8
  id: 1,
  email: "[email protected]",
  encrypted_password: "$2a$11$rvOrK1bmuuNwwc78ERxG3eCrKiUu9NTZsJ/nmirqb.3yRBHYUK69S",
  reset_password_token: nil,
  reset_password_sent_at: nil,
  remember_created_at: nil,
  sign_in_count: 0,
  current_sign_in_at: nil,
  last_sign_in_at: nil,
  current_sign_in_ip: nil,
  last_sign_in_ip: nil,
  created_at: Mon, 11 Apr 2016 10:35:39 UTC +00:00,
  updated_at: Mon, 11 Apr 2016 10:35:39 UTC +00:00>]

Yet this is the error I get in my rails console:

ActionController::RoutingError (No route matches [GET] "/users/1"):

actionpack (5.0.0.beta3) lib/action_dispatch/middleware/debug_exceptions.rb:53:in `call'
web-console (3.1.1) lib/web_console/middleware.rb:131:in `call_app'
web-console (3.1.1) lib/web_console/middleware.rb:28:in `block in call'
web-console (3.1.1) lib/web_console/middleware.rb:18:in `catch'
web-console (3.1.1) lib/web_console/middleware.rb:18:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:36:in `call_app'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `block in call'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `block in tagged'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `tagged'
railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/request_id.rb:24:in `call'
rack (2.0.0.alpha) lib/rack/runtime.rb:22:in `call'
activesupport (5.0.0.beta3) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/load_interlock.rb:13:in `call'
actionpack (5.0.0.beta3) lib/action_dispatch/middleware/static.rb:136:in `call'
rack (2.0.0.alpha) lib/rack/sendfile.rb:111:in `call'
railties (5.0.0.beta3) lib/rails/engine.rb:522:in `call'
puma (3.2.0) lib/puma/configuration.rb:227:in `call'
puma (3.2.0) lib/puma/server.rb:561:in `handle_request'
puma (3.2.0) lib/puma/server.rb:406:in `process_client'
puma (3.2.0) lib/puma/server.rb:271:in `block in run'
puma (3.2.0) lib/puma/thread_pool.rb:111:in `block in spawn_thread'

And this is what I see in my browser:

{"status":404,"error":"Not Found","exception":"#\u003cActionController::RoutingError: No route matches [GET] \"/users/1\"\u003e","traces":{"Application Trace":[],"Framework Trace":[{"id":0,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/debug_exceptions.rb:53:in `call'"},{"id":1,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:131:in `call_app'"},{"id":2,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:28:in `block in call'"},{"id":3,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:18:in `catch'"},{"id":4,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:18:in `call'"},{"id":5,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'"},{"id":6,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:36:in `call_app'"},{"id":7,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `block in call'"},{"id":8,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `block in tagged'"},{"id":9,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:26:in `tagged'"},{"id":10,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `tagged'"},{"id":11,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `call'"},{"id":12,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/request_id.rb:24:in `call'"},{"id":13,"trace":"rack (2.0.0.alpha) lib/rack/runtime.rb:22:in `call'"},{"id":14,"trace":"activesupport (5.0.0.beta3) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'"},{"id":15,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/load_interlock.rb:13:in `call'"},{"id":16,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/static.rb:136:in `call'"},{"id":17,"trace":"rack (2.0.0.alpha) lib/rack/sendfile.rb:111:in `call'"},{"id":18,"trace":"railties (5.0.0.beta3) lib/rails/engine.rb:522:in `call'"},{"id":19,"trace":"puma (3.2.0) lib/puma/configuration.rb:227:in `call'"},{"id":20,"trace":"puma (3.2.0) lib/puma/server.rb:561:in `handle_request'"},{"id":21,"trace":"puma (3.2.0) lib/puma/server.rb:406:in `process_client'"},{"id":22,"trace":"puma (3.2.0) lib/puma/server.rb:271:in `block in run'"},{"id":23,"trace":"puma (3.2.0) lib/puma/thread_pool.rb:111:in `block in spawn_thread'"}],"Full Trace":[{"id":0,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/debug_exceptions.rb:53:in `call'"},{"id":1,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:131:in `call_app'"},{"id":2,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:28:in `block in call'"},{"id":3,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:18:in `catch'"},{"id":4,"trace":"web-console (3.1.1) lib/web_console/middleware.rb:18:in `call'"},{"id":5,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/show_exceptions.rb:31:in `call'"},{"id":6,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:36:in `call_app'"},{"id":7,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `block in call'"},{"id":8,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `block in tagged'"},{"id":9,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:26:in `tagged'"},{"id":10,"trace":"activesupport (5.0.0.beta3) lib/active_support/tagged_logging.rb:70:in `tagged'"},{"id":11,"trace":"railties (5.0.0.beta3) lib/rails/rack/logger.rb:24:in `call'"},{"id":12,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/request_id.rb:24:in `call'"},{"id":13,"trace":"rack (2.0.0.alpha) lib/rack/runtime.rb:22:in `call'"},{"id":14,"trace":"activesupport (5.0.0.beta3) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'"},{"id":15,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/load_interlock.rb:13:in `call'"},{"id":16,"trace":"actionpack (5.0.0.beta3) lib/action_dispatch/middleware/static.rb:136:in `call'"},{"id":17,"trace":"rack (2.0.0.alpha) lib/rack/sendfile.rb:111:in `call'"},{"id":18,"trace":"railties (5.0.0.beta3) lib/rails/engine.rb:522:in `call'"},{"id":19,"trace":"puma (3.2.0) lib/puma/configuration.rb:227:in `call'"},{"id":20,"trace":"puma (3.2.0) lib/puma/server.rb:561:in `handle_request'"},{"id":21,"trace":"puma (3.2.0) lib/puma/server.rb:406:in `process_client'"},{"id":22,"trace":"puma (3.2.0) lib/puma/server.rb:271:in `block in run'"},{"id":23,"trace":"puma (3.2.0) lib/puma/thread_pool.rb:111:in `block in spawn_thread'"}]}}

Edit 1

This is my rake routes

$ rake routes
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead.
                  Prefix Verb   URI Pattern                    Controller#Action
        new_user_session GET    /users/sign_in(.:format)       devise/sessions#new
            user_session POST   /users/sign_in(.:format)       devise/sessions#create
    destroy_user_session DELETE /users/sign_out(.:format)      devise/sessions#destroy
           user_password POST   /users/password(.:format)      devise/passwords#create
       new_user_password GET    /users/password/new(.:format)  devise/passwords#new
      edit_user_password GET    /users/password/edit(.:format) devise/passwords#edit
                         PATCH  /users/password(.:format)      devise/passwords#update
                         PUT    /users/password(.:format)      devise/passwords#update
cancel_user_registration GET    /users/cancel(.:format)        devise/registrations#cancel
       user_registration POST   /users(.:format)               devise/registrations#create
   new_user_registration GET    /users/sign_up(.:format)       devise/registrations#new
  edit_user_registration GET    /users/edit(.:format)          devise/registrations#edit
                         PATCH  /users(.:format)               devise/registrations#update
                         PUT    /users(.:format)               devise/registrations#update
                         DELETE /users(.:format)               devise/registrations#destroy
                api_user GET    /users/:id(.:format)           api/v1/users#show {:format=>:json, :subdomain=>"api"}

Edit 2

This is my application controller:

class ApplicationController < ActionController::API
end

Edit 3

This is my users_controller_spec.rb test that actually passes:

require 'rails_helper'

describe Api::V1::UsersController do
  before(:each) { request.headers['Accept'] = "application/vnd.myapp.v1" }

  describe "GET #show" do
    before(:each) do
      @user = FactoryGirl.create :user
      get :show, id: @user.id, format: :json
    end

    it "returns the information about a user on a hash" do
      user_response = JSON.parse(response.body, symbolize_names: true)
      expect(user_response[:email]).to eql @user.email
    end

    it { should respond_with 200 }
  end

end

This is the result:

$ rspec spec/controllers
DEPRECATION WARNING: use_transactional_fixtures= is deprecated and will be removed from Rails 5.1 (use use_transactional_tests= instead). (called from <top (required)> at /myapp/spec/controllers/api/v1/users_controller_spec.rb:3)
DEPRECATION WARNING: ActionController::TestCase HTTP request methods will accept only
keyword arguments in future Rails versions.

Examples:

get :show, params: { id: 1 }, session: { user_id: 1 }
process :update, method: :post, params: { id: 1 }
 (called from block (3 levels) in <top (required)> at /myapp/spec/controllers/api/v1/users_controller_spec.rb:9)
DEPRECATION WARNING: ActionController::TestCase HTTP request methods will accept only
keyword arguments in future Rails versions.

Examples:

get :show, params: { id: 1 }, session: { user_id: 1 }
process :update, method: :post, params: { id: 1 }
 (called from block (3 levels) in <top (required)> at /myapp/spec/controllers/api/v1/users_controller_spec.rb:9)
.DEPRECATION WARNING: ActionController::TestCase HTTP request methods will accept only
keyword arguments in future Rails versions.

Examples:

get :show, params: { id: 1 }, session: { user_id: 1 }
process :update, method: :post, params: { id: 1 }
 (called from block (3 levels) in <top (required)> at /myapp/spec/controllers/api/v1/users_controller_spec.rb:9)
DEPRECATION WARNING: ActionController::TestCase HTTP request methods will accept only
keyword arguments in future Rails versions.

Examples:

get :show, params: { id: 1 }, session: { user_id: 1 }
process :update, method: :post, params: { id: 1 }
 (called from block (3 levels) in <top (required)> at /myapp/spec/controllers/api/v1/users_controller_spec.rb:9)
.

Finished in 0.41411 seconds (files took 3.33 seconds to load)
2 examples, 0 failures

Answer 1

The problem is that your route has a constraint requiring a subdomain of api. So http://api.lvh.me:3000/users/1.json will work, but not http://localhost:3000/users/1.json or http://lvh.me:3000/users/1.json.

You should change your Ajax call to use an api subdomain. You can also confirm this by writing a request test (not a controller test), and see that it gets a 200 when using an api subdomain, and a 404 otherwise.