We’re now using `contract` as the first step and validations for
mandatory parameters have been added.
To simplify specs a bit, we only assert the service contract is run as
expected without testing each validation case. We’re now testing the
contract itself in isolation.
This is a combined work of Martin Brennan, Loïc Guitaut, and Joffrey Jaffeux.
---
This commit implements a base service object when working in chat. The documentation is available at https://discourse.github.io/discourse/chat/backend/Chat/Service.html
Generating documentation has been made as part of this commit with a bigger goal in mind of generally making it easier to dive into the chat project.
Working with services generally involves 3 parts:
- The service object itself, which is a series of steps where few of them are specialized (model, transaction, policy)
```ruby
class UpdateAge
include Chat::Service::Base
model :user, :fetch_user
policy :can_see_user
contract
step :update_age
class Contract
attribute :age, :integer
end
def fetch_user(user_id:, **)
User.find_by(id: user_id)
end
def can_see_user(guardian:, **)
guardian.can_see_user(user)
end
def update_age(age:, **)
user.update!(age: age)
end
end
```
- The `with_service` controller helper, handling success and failure of the service within a service and making easy to return proper response to it from the controller
```ruby
def update
with_service(UpdateAge) do
on_success { render_serialized(result.user, BasicUserSerializer, root: "user") }
end
end
```
- Rspec matchers and steps inspector, improving the dev experience while creating specs for a service
```ruby
RSpec.describe(UpdateAge) do
subject(:result) do
described_class.call(guardian: guardian, user_id: user.id, age: age)
end
fab!(:user) { Fabricate(:user) }
fab!(:current_user) { Fabricate(:admin) }
let(:guardian) { Guardian.new(current_user) }
let(:age) { 1 }
it { expect(user.reload.age).to eq(age) }
end
```
Note in case of unexpected failure in your spec, the output will give all the relevant information:
```
1) UpdateAge when no channel_id is given is expected to fail to find a model named 'user'
Failure/Error: it { is_expected.to fail_to_find_a_model(:user) }
Expected model 'foo' (key: 'result.model.user') was not found in the result object.
[1/4] [model] 'user' ❌
[2/4] [policy] 'can_see_user'
[3/4] [contract] 'default'
[4/4] [step] 'update_age'
/Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/update_age.rb:32:in `fetch_user': missing keyword: :user_id (ArgumentError)
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:202:in `instance_exec'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:202:in `call'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:219:in `call'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `block in run!'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `each'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `run!'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:411:in `run'
from <internal:kernel>:90:in `tap'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:302:in `call'
from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/spec/services/update_age_spec.rb:15:in `block (3 levels) in <main>'
```
Loïc Guitaut
Martin Brennan