Make PushOptions a cross-domain framework

Problem

We are using push options as Hash object in many parts of the application and this has turned into a Primitive Obsession. Push options is more of a framework for passing data to GitLab backend via git push. Today we have various types of data (namespaces) of push options such as ci, merge_request, integrations, etc.

While groupsource code would own the framework (of passing data), each data namespace should be owned by various domains. The proposal below can be one way we could solve this in a modularized way.

Context

This issue is extracted from a code review where we introduced a CI-specific push options class rather than having specific parser logic defined in Git::BaseHooksService.

The following discussion from !186297 (merged) should be addressed:

• @fabiopitino started a discussion:

  non-blocking: I just realized that we do have Gitlab::PushOptions object that that is used in PostReceiveService https://gitlab.com/gitlab-org/gitlab/-/blob/c5c3ed711c5f47a4d872ecd63ad86451b09be56e/app/services/post_receive_service.rb#L61 but later it's pushed to the PostReceive Sidekiq worker as JSON and from there on we use it as Hash.

  It would be great to have a SSoT for dealing with push options but it would require an even bigger refactoring because:

  • Gitlab::PushOptions expects options in Array form (as it comes from Gitaly).
  • The initializer of Gitlab::PushOptions is primarily a parser. The rest of the class is a basic access object.
  • We could have Gitlab::PushOptions to be a SSoT for serialized and deserialized options
  • Each domain could implement their own Push Options namespace (e.g. ci.*) and be responsible for it.
  • The groupsource code would be responsible for the general push options framework while each team owns their own namespace

  class Gitlab::PushOptions
    def self.fabricate(push_options)
      # handle: array (gitaly), hash/json, PushOptions object, nil
    end
  
    NAMESPACES = {
      ci: ::Ci::PushOptions, # each domain owns their own push options
      merge_request: ::MergeRequests::PushOptions,
      # ...
    }
  
    def initialize(data)
      @data = data
      @opts = {}
  
      NAMESPACES.each do |namespace, handler|
        @opts[namespace] = handler.new(data.fetch(namespace.to_sym, {})) 
      end
  
      @opts.each(&:validate!)
    end
  
    def ci
      @opts.fetch(:ci)
    end
  
    def merge_request
      @opts.fetch(:merge_request)
    end
  
    def as_json(*_args)
      @data.as_json
    end
  end
  
  class Gitlab::PushOptions::Namespace
    def initialize(data)
      @data = data
    end
  
    def validate!
      # use locally defined ALLOWED_OPTIONS and MULTI_VALUE_OPTIONS
    end
  end
  
  class Ci::PushOptions < Gitlab::PushOptions::Namespace
    ALLOWED_OPTIONS = [:skip, :variable, :input]
    MULTI_VALUE_OPTIONS = [:input, :variable]
  
    def skip?
      data[:skip].present?
    end
  
    def variables
      # ...
    end
  
    def inputs
      # ...
    end
  end
  
  ####
  # Usage:
  push_options = Gitlab::PushOptions.fabricate(data)
  push_options.ci.skip? # => false
  push_options.ci.inputs # => { foo: 'bar' }
  push_options.merge_request.labels # => ['foo', 'bar']
  push_options.secret_push_protection.skip_all? # => true
  push_options.as_json # => { ... }