Inserting yield() into form_for() raises an error uncaught by test

Question

I'm following the http://railstutorial.org. I finished everything up to 10.2 section excluded. Then I encountered some kind of a problem. My current application codes are below.

Exercise 2 in section 7.3.4 made me add some additional code to application. As a result I had to update routes and create my very own solution to exercise 2 in section 10.1.1 (author suggested using yield and provide methods, which I did - seen in codes). After doing so I created a test for successful and unsuccessful edit of user (section 10.1.3 and 10.1.4). Both tests passed, but my application wasn't working as expected.

Problem description: When I log in (not required though, authorization is a goal of 10.2 section) and go to edit page /users/:id/edit, site works. When I press "Save changes" button, it returns an error (no matter which user I try to edit):

No route matches [PATCH] "/users/1/edit"
Rails.root: /home/akazecik/workspace/sample_app

and all tests pass.

On the other hand, when I replace @user with user_path(@user) in edit.html.erb file, the error is gone and site works fine. All test still pass.

On the 'third hand' when I replace yield(:needed_link) with @user in _form.html.erb file (and therefore omit the use of yield method from first case) and ignore non-passing test (obvious thing):

FAIL["test_invalid_signup_information", UsersSignupTest, 0.5256564110004547]
test_invalid_signup_information#UsersSignupTest (0.53s)
        Expected at least 1 element matching "form[action="/signup"]", found 0..
        Expected 0 to be >= 1.
        test/integration/users_signup_test.rb:6:in `block in <class:UsersSignupTest>'

I again get working site and the rest of tests seem to pass.

---

So my questions are:

• Why are the tests passing even though my site isn't working? Why is the users_edit_test.rb able to update the user, even though I can't?
• What is the difference between @user and yield(:needed_link) with provide(:needed_link, @user)?
• Right at the beginning of section 10.2 we read that actions edit and update:

they allow anyone (even non-logged-in users) to access either action, and any logged-in user can update the information for any other user

That is not the case, because I can UPDATE information even as a non-logged-in user. What am I missing? By logged-in, I mean that logged_in? method in app/helpers/sessions_helper.rb returns true.

---

/app/views/users/new.html.erb

<% provide(:title, 'Sign up') %>
<% provide(:button_text, 'Create my account') %>
<% provide(:needed_link, signup_path) %>
<h1>Sign up</h1>
<div class="row">
  <div class="col-md-6 col-md-offset-3">
    <%= render 'form' %>
  </div>
</div>

/app/views/users/edit.html.erb

<% provide(:title, 'Edit user') %>
<% provide(:button_text, 'Save changes') %>
<% provide(:needed_link, @user) %>
<h1>Update your profile</h1>
<div class="row">
  <div class="col-md-6 col-md-offset-3">
    <%= render 'form' %>
    <div class="gravatar_edit">
      <%= gravatar_for @user %>
      <a href="http://gravatar.com/emails" target="_blank">Change</a>
    </div>
  </div>
</div>

/app/views/users/_form.html.erb

<%= form_for(@user, url: yield(:needed_link)) do |f| %>
  <%= render 'shared/error_messages', object: @user %>

  <%= f.label :name %>
  <%= f.text_field :name, class: 'form-control' %>

  <%= f.label :email %>
  <%= f.email_field :email, class: 'form-control' %>

  <%= f.label :password %>
  <%= f.password_field :password, class: 'form-control' %>

  <%= f.label :password_confirmation %>
  <%= f.password_field :password_confirmation, class: 'form-control' %>

  <%= f.submit yield(:button_text), class: "btn btn-primary" %>
<% end %>

app/controllers/users_controller.rb

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
  end
  def new
    @user = User.new
  end
  def create
    @user = User.new(user_params)     # Not the final implementation!
    if @user.save
      log_in @user
        flash[:success] = "Welcome to the Sample App!"
        redirect_to user_url(@user)
    else
        render 'new'
    end
  end
  def edit
    @user = User.find(params[:id])
  end
  def update
    @user = User.find(params[:id])
    if @user.update_attributes(user_params)
      flash[:success] = "Profile updated"
      redirect_to user_path(@user)
    else
      render 'edit'
    end
  end
  private
      def user_params
        params.require(:user).permit(:name, :email, :password, :password_confirmation)
    end
end

test/integration/users_edit_test.rb

require 'test_helper'

class UsersEditTest < ActionDispatch::IntegrationTest
  def setup
    @user = users(:michael)
  end

  test "unsuccessful edit" do
    get edit_user_path(@user)
    assert_template 'users/edit'
    patch user_path(@user), params: {user: { name: "", email: "foo@invalid", password: "foo", password_confirmation: "bar" } }
    assert_template 'users/edit'
    assert_select 'div.alert', "The form contains 4 errors."
  end

  test "successful edit" do
    get edit_user_path(@user)
    assert_template 'users/edit'
    name  = "Foo Bar"
    email = "foo@bar.com"
    patch user_path(@user), params: { user: { name:  name,
                                              email: email,
                                              password:              "",
                                              password_confirmation: "" } }
    assert_not flash.empty?
    assert_redirected_to @user
    @user.reload
    assert_equal name,  @user.name
    assert_equal email, @user.email
  end
end

test/fixtures/users.yml

michael:
  name: Michael Example
  email: michael@example.com
  password_digest: <%= User.digest('password') %>

app/helpers/sessions_helper.rb

module SessionsHelper
    # Logs in the given user.
    def log_in(user)
        session[:user_id] = user.id
    end

  # Remembers a user in a persistent session.
  def remember(user)
    user.remember
    cookies.permanent.signed[:user_id] = user.id
    cookies.permanent[:remember_token] = user.remember_token
  end

    # Returns the current logged-in user (if any).
    def current_user
      if (user_id = session[:user_id])
        @current_user ||= User.find_by(id: user_id)
      elsif (user_id = cookies.signed[:user_id])
        user = User.find_by(id: user_id)
        if user && user.authenticated?(cookies[:remember_token])
          log_in user
          @current_user = user
        end
      end
    end

    # Returns true if the user is logged in, false otherwise.
    def logged_in?
        !current_user.nil?
    end

  # Forgets a persistent session.
  def forget(user)
    user.forget
    cookies.delete(:user_id)
    cookies.delete(:remember_token)
  end

  # Logs out the current user.
  def log_out
    forget(current_user)
    session.delete(:user_id)
    @current_user = nil
  end
end

Answer 1

<% provide(:needed_link, @user) %>

@user isn't a link - it is a user instance. You can pass an instance of a model to a link-generating-method (eg render in a controller or link_to in a template) and the method uses Rails-magic* to turn the model into a link... but it isn't a link of itself, so if you try to use it in a place that isn't one of the special (unwritten) methods... it won't work.

This might be why the :link_needed stuff isn't working the way you'd expect.

The url for a form is probably just not one of those methods... so you need to actually create the link using the edit_user_path(@user) method instead.

* behind-the-scenes, some rails methods call url_for on a model to turn it into a proper link - but only some methods.