Rails 7 signup form doesn't show error messages - ruby-on-rails

Question

I am following a rails tutorial, in the signup form, if invalid user info is submitted, the signup page is supposed to be re-rendered with error messages, but actually it doesn't. It seems that even if the signup page is rendered by "render 'new'", the #user passed to it is empty. How to fix this?
Please note that the tutorial uses Rails 6 but I'm actually using Rails 7.0.2.3 with Ruby 3.1.1. Not sure if this is the cause.
app/controllers/users_controller.rb
class UsersController < ApplicationController
def new
#user = User.new
end
def create
#user = User.new(user_params)
if #user.save
else
render 'new'
end
end
def show
#user = User.find(params[:id])
end
private
def user_params
params.require(:user).permit(:name, :email, :password, :password_confirmation)
end
end
app/views/users/new.html.erb
<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= form_with(model: #user, local: true) do |f| %>
<%= render 'shared/error_messages' %>
<%= 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, "Confirmation" %>
<%= f.password_field :password_confirmation, class: 'form-control' %>
<%= f.submit "Create my account", class: "btn btn-primary" %>
<% end %>
</div>
</div>
app/views/shared/_error_messages.html.erb
<% if #user.errors.any? %>
<div id="error_explanation">
<div class="alert alert-danger">
The form contains <%= pluralize(#user.errors.count, "error") %>.
</div>
<ul>
<% #user.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
app/assets/stylesheets/custom.scss
#import "bootstrap-sprockets";
#import "bootstrap";
/* variables */
$gray-medium-light: #eaeaea;
/* mixins */
#mixin box_sizing {
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
box-sizing: border-box;
}
/* miscellaneous */
.debug_dump {
clear: both;
float: left;
width: 100%;
margin-top: 45px;
#include box_sizing;
}
/* universal */
body {
padding-top: 60px;
}
section {
overflow: auto;
}
textarea {
resize: vertical;
}
.center {
text-align: center;
h1 {
margin-bottom: 10px;
}
}
/* typography */
h1, h2, h3, h4, h5, h6 {
line-height: 1;
}
h1 {
font-size: 3em;
letter-spacing: -2px;
margin-bottom: 30px;
text-align: center;
}
h2 {
font-size: 1.2em;
letter-spacing: -1px;
margin-bottom: 30px;
text-align: center;
font-weight: normal;
color: $gray-light;
}
p {
font-size: 1.1em;
line-height: 1.7em;
}
/* header */
#logo {
float: left;
margin-right: 10px;
font-size: 1.7em;
color: white;
text-transform: uppercase;
letter-spacing: -1px;
padding-top: 9px;
font-weight: bold;
&:hover {
color: white;
text-decoration: none;
}
}
/* footer */
footer {
margin-top: 45px;
padding-top: 5px;
border-top: 1px solid $gray-medium-light;
color: $gray-light;
a {
color: $gray;
&:hover {
color: $gray-darker;
}
}
small {
float: left;
}
ul {
float: right;
list-style: none;
li {
float: left;
margin-left: 15px;
}
}
}
/* sidebar */
aside {
section.user_info {
margin-top: 20px;
}
section {
padding: 10px 0;
margin-top: 20px;
&:first-child {
border: 0;
padding-top: 0;
}
span {
display: block;
margin-bottom: 3px;
line-height: 1;
}
h1 {
font-size: 1.4em;
text-align: left;
letter-spacing: -1px;
margin-bottom: 3px;
margin-top: 0px;
}
}
}
.gravatar {
float: left;
margin-right: 10px;
}
.gravatar_edit {
margin-top: 15px;
}
/* forms */
input, textarea, select, .uneditable-input {
border: 1px solid #bbb;
width: 100%;
margin-bottom: 15px;
#include box_sizing;
}
input {
height: auto !important;
}
#error_explanation {
color: red;
ul {
color: red;
margin: 0 0 30px 0;
}
}
.field_with_errors {
#extend .has-error;
.form-control {
color: $state-danger-text;
}
}
Debug info of rails server when form submit button is clicked with invalid
Started POST "/users" for ::1 at 2022-04-06 00:55:04
Processing by UsersController#create as TURBO_STREAM
Parameters: {"authenticity_token"=>"[FILTERED]", "user"=>{"name"=>"foo123", "email"=>"foo123#asdf", "password"=>"[FILTERED]", "password_confirmation"=>"[FILTERED]"}, "commit"=>"Create my account"}
TRANSACTION (0.0ms) begin transaction
↳ app/controllers/users_controller.rb:8:in `create'
User Exists? (0.1ms) SELECT 1 AS one FROM "users" WHERE "users"."email" = ? LIMIT ? [["email", "foo123#asdf"], ["LIMIT", 1]]
↳ app/controllers/users_controller.rb:8:in `create'
TRANSACTION (0.0ms) rollback transaction
↳ app/controllers/users_controller.rb:8:in `create'
Rendering layout layouts/application.html.erb
Rendering users/new.html.erb within layouts/application
Rendered shared/_error_messages.html.erb (Duration: 0.4ms | Allocations: 403)
Rendered users/new.html.erb within layouts/application (Duration: 1.9ms | Allocations: 1891)
Rendered layouts/_shim.html.erb (Duration: 0.0ms | Allocations: 15)
Rendered layouts/_header.html.erb (Duration: 0.1ms | Allocations: 78)
Rendered layouts/_footer.html.erb (Duration: 0.1ms | Allocations: 51)
Rendered layout layouts/application.html.erb (Duration: 9.5ms | Allocations: 8695)
Completed 200 OK in 213ms (Views: 9.8ms | ActiveRecord: 0.2ms | Allocations: 11628)

Answer 1

In rails 7 forms are submitting as TURBO_STREAM by default. After submitting a form Turbo expects a redirect unless response status is in 400-599 range.
render :new # default status is 200
With status code 200 Turbo shows an error in the browser console and page doesn't re-render.
To make Turbo accept rendered html, change the response status. Default seems to be :unprocessable_entity (status code 422)
render :new, status: :unprocessable_entity
https://turbo.hotwired.dev/handbook/drive#redirecting-after-a-form-submission
https://github.com/hotwired/turbo/commit/4670f2b57c5d0246dfc0f6d10ff7d9a52a63fdca
Update: a note on "Content-Type". This applies to default form submission with turbo.
In this set up turbo is expecting an html response with Content-Type: text/html;. #puerile noted that omitting .html extension in your views also breaks the response.
Rails uses .html extension to set response content type to text/html. When extension is omitted content type is set to text/vnd.turbo-stream.html because the form is submitted as TURBO_STREAM, since our response doesn't have a <turbo-stream> it is the wrong content type.
>> Mime[:turbo_stream].to_str
=> "text/vnd.turbo-stream.html"
If we have a view views/users/new.erb, this will not work:
if #user.save
redirect_to #user
else
# NOTE: this will render `new.erb` and set
# `Content-Type: text/vnd.turbo-stream.html` header;
# turbo is not happy.
render :new, status: :unprocessable_entity
end
To fix it, use respond_to method:
respond_to do |format|
if #user.save
format.html { redirect_to #user }
else
# NOTE: this will render `new.erb` and set
# `Content-Type: text/html` header;
# turbo is happy.
format.html { render(:new, status: :unprocessable_entity) }
end
end
or set content type manually:
if #user.save
redirect_to #user
else
render :new, status: :unprocessable_entity, content_type: "text/html"
# NOTE: you can also set headers like this
headers["Content-Type"] = "text/html"
end
One caveat with the last set up is that the layout has to be without .html extension as well, otherwise, render :new will render new.erb without a layout and turbo won't be happy again. This is not an issue when using respond_to method.
https://api.rubyonrails.org/classes/ActionController/MimeResponds.html#method-i-respond_to

Answer 2

If you look at the logs you can see that Rails is getting an AJAX request in the form of a turbo stream:
Processing by UsersController#create as TURBO_STREAM
Where it should read:
Processing by UsersController#create as HTML
To disable turbo you want need to set a data-turbo="false" attribute on the form:
<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= form_with(model: #user, data: { turbo: false }) do |f| %>
<%= render 'shared/error_messages' %>
<%= 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, "Confirmation" %>
<%= f.password_field :password_confirmation, class: 'form-control' %>
<%= f.submit "Create my account", class: "btn btn-primary" %>
<% end %>
</div>
</div>
The local: false option only works with the old Rails UJS javascript library which was the default prior to Rails 7. You can also disable Turbo by default with:
import { Turbo } from "#hotwired/turbo-rails"
Turbo.session.drive = false
See:
https://turbo.hotwired.dev/handbook/drive#disabling-turbo-drive-on-specific-links-or-forms