4.6 KiB
API styleguide
This styleguide recommends best practices for API development.
Instance variables
Please do not use instance variables, there is no need for them (we don't need to access them as we do in Rails views), local variables are fine.
Entities
Always use an Entity to present the endpoint's payload.
Documentation
API endpoints must come with documentation, unless it is internal or behind a feature flag. The docs should be in the same merge request, or, if strictly necessary, in a follow-up with the same milestone as the original merge request.
Methods and parameters description
Every method must be described using the Grape DSL (see https://gitlab.com/gitlab-org/gitlab/blob/master/lib/api/environments.rb for a good example):
-
desc
for the method summary. You should pass it a block for additional details such as:- The GitLab version when the endpoint was added. If it is behind a feature flag, mention that instead: This feature is gated by the :feature_flag_symbol feature flag.
- If the endpoint is deprecated, and if so, when will it be removed
-
params
for the method params. This acts as description, validation, and coercion of the parameters
A good example is as follows:
desc 'Get all broadcast messages' do
detail 'This feature was introduced in GitLab 8.12.'
success Entities::BroadcastMessage
end
params do
optional :page, type: Integer, desc: 'Current page number'
optional :per_page, type: Integer, desc: 'Number of messages per page'
end
get do
messages = BroadcastMessage.all
present paginate(messages), with: Entities::BroadcastMessage
end
Declared params
Grape allows you to access only the parameters that have been declared by your
params
block. It filters out the params that have been passed, but are not allowed.
– https://github.com/ruby-grape/grape#declared
Exclude params from parent namespaces
By default
declared(params)
includes parameters that were defined in all parent namespaces.
– https://github.com/ruby-grape/grape#include-parent-namespaces
In most cases you will want to exclude params from the parent namespaces:
declared(params, include_parent_namespaces: false)
When to use declared(params)
You should always use declared(params)
when you pass the params hash as
arguments to a method call.
For instance:
# bad
User.create(params) # imagine the user submitted `admin=1`... :)
# good
User.create(declared(params, include_parent_namespaces: false).to_h)
Note:
declared(params)
return aHashie::Mash
object, on which you will have to call.to_h
.
But we can use params[key]
directly when we access single elements.
For instance:
# good
Model.create(foo: params[:foo])
Using HTTP status helpers
For non-200 HTTP responses, use the provided helpers in lib/api/helpers.rb
to ensure correct behaviour (not_found!
, no_content!
etc.). These will throw
inside Grape and abort the execution of your endpoint.
For DELETE
requests, you should also generally use the destroy_conditionally!
helper which by default returns a 204 No Content
response on success, or a 412 Precondition Failed
response if the given If-Unmodified-Since
header is out of range. This helper calls #destroy
on the passed resource, but you can also implement a custom deletion method by passing a block.
Using API path helpers in GitLab Rails codebase
Because we support installing GitLab under a relative URL, one must take this
into account when using API path helpers generated by Grape. Any such API path
helper usage must be in wrapped into the expose_path
helper call.
For instance:
- endpoint = expose_path(api_v4_projects_issues_related_merge_requests_path(id: @project.id, issue_iid: @issue.iid))
Internal API
The internal API is documented for internal use. Please keep it up to date so we know what endpoints different components are making use of.
Testing
When writing tests for new API endpoints, consider using a schema fixture located in /spec/fixtures/api/schemas
. You can expect
a response to match a given schema:
expect(response).to match_response_schema('merge_requests')