#devise_for should handle NoDatabaseError gracefully

[cryptogopher]

Once Devise routes are configured using #devise_for, they are created always when application starts. #devise_for causes associated model to be loaded. If - for some reason - the model needs access to database on load, #devise_for causes unhandled exception if database does not exist. That effectively makes impossible to create non-existing database once #devise_for is added to routes.

Example:

routes.rb:

...
devise_for :users
...

app/models/user.rb:

...
validates :email, presence: true, uniqueness: true, length: {maximum: type_for_attribute(:email).limit}
...

Now, when trying to execute below command, unhandled exception happens:

rails db:create
bin/rails aborted!
ActiveRecord::NoDatabaseError: We could not find your database: database_name. Available database configurations can be found in config/database.yml. (ActiveRecord::NoDatabaseError)

To resolve this error:

- Did you not create the database, or did you delete it? To create the database, run:

    bin/rails db:create

- Has the database name changed? Verify that config/database.yml contains the correct database name.

Database can only be created if #devise_for is temporarily removed from routes.

Fragment of backtrace between #devise_for call and model loading:

...
/var/www/app/models/user.rb:1:in `<top (required)>'
/var/www/.gem/ruby/3.3.0/gems/zeitwerk-2.7.2/lib/zeitwerk/core_ext/kernel.rb:26:in `require'
/var/www/.gem/ruby/3.3.0/gems/activesupport-7.2.2.1/lib/active_support/inflector/methods.rb:290:in `const_get'
/var/www/.gem/ruby/3.3.0/gems/activesupport-7.2.2.1/lib/active_support/inflector/methods.rb:290:in `constantize'
/var/www/.gem/ruby/3.3.0/gems/activesupport-7.2.2.1/lib/active_support/core_ext/string/inflections.rb:74:in `constantize'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise.rb:327:in `get'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/mapping.rb:83:in `to'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/mapping.rb:78:in `modules'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/mapping.rb:95:in `routes'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/mapping.rb:162:in `default_used_route'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/mapping.rb:72:in `initialize'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise.rb:361:in `new'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise.rb:361:in `add_mapping'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/rails/routes.rb:243:in `block in devise_for'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/rails/routes.rb:242:in `each'
/var/www/.gem/ruby/3.3.0/gems/devise-4.9.4/lib/devise/rails/routes.rb:242:in `devise_for'
/var/www/config/routes.rb:23:in `block in <top (required)>'
...