Expose IDs in GraphQL as a GlobalID

This exposes all fields named `id` as GlobalIDs so they can be used
across our entire GraphQL implementation.

When the objects loaded are `ApplicationRecord`s. We'll use our
existing batchloading to find them. Otherwise, we'll fall back to the
default implementation of `GlobalID`: Calling the `.find` method on
the class.

2 files changed, 30 insertions, 0 deletions

diff --git a/app/graphql/gitlab_schema.rb b/app/graphql/gitlab_schema.rb
index f8ad6bee21b..2e5bdbd79c8 100644
--- a/app/graphql/gitlab_schema.rb
+++ b/app/graphql/gitlab_schema.rb
@@ -45,6 +45,31 @@ class GitlabSchema < GraphQL::Schema
       super(query_str, **kwargs)
     end
 
+    def id_from_object(object)
+      unless object.respond_to?(:to_global_id)
+        # This is an error in our schema and needs to be solved. So raise a
+        # more meaningfull error message
+        raise "#{object} does not implement `to_global_id`. "\
+              "Include `GlobalID::Identification` into `#{object.class}"
+      end
+
+      object.to_global_id
+    end
+
+    def object_from_id(global_id)
+      gid = GlobalID.parse(global_id)
+
+      unless gid
+        raise Gitlab::Graphql::Errors::ArgumentError, "#{global_id} is not a valid GitLab id."
+      end
+
+      if gid.model_class < ApplicationRecord
+        Gitlab::Graphql::Loaders::BatchModelLoader.new(gid.model_class, gid.model_id).find
+      else
+        gid.find
+      end
+    end
+
     private
 
     def max_query_complexity(ctx)
diff --git a/app/graphql/types/base_object.rb b/app/graphql/types/base_object.rb
index 82b78abd573..e40059c46bb 100644
--- a/app/graphql/types/base_object.rb
+++ b/app/graphql/types/base_object.rb
@@ -6,5 +6,10 @@ module Types
     prepend Gitlab::Graphql::ExposePermissions
 
     field_class Types::BaseField
+
+    # All graphql fields exposing an id, should expose a global id.
+    def id
+      GitlabSchema.id_from_object(object)
+    end
   end
 end