Support empty GIDsnil-safe-object_from_id

In places we use the pattern `gid ? object_from_id(gid) : nil`, which
is a bit confusing to read. Such usages can be improved by providing a
separate method which allows non-present arguments, returning nil when
so called.

2 files changed, 29 insertions, 0 deletions

diff --git a/app/graphql/gitlab_schema.rb b/app/graphql/gitlab_schema.rb
index 7edd14e48f7..ac04eff44c1 100644
--- a/app/graphql/gitlab_schema.rb
+++ b/app/graphql/gitlab_schema.rb
@@ -57,6 +57,10 @@ class GitlabSchema < GraphQL::Schema
       object.to_global_id
     end
 
+    def object_from_id_when_present(global_id)
+      object_from_id(global_id) if global_id.present?
+    end
+
     def object_from_id(global_id)
       gid = GlobalID.parse(global_id)
 
diff --git a/spec/graphql/gitlab_schema_spec.rb b/spec/graphql/gitlab_schema_spec.rb
index dec6b23d72a..d101a3fd109 100644
--- a/spec/graphql/gitlab_schema_spec.rb
+++ b/spec/graphql/gitlab_schema_spec.rb
@@ -122,6 +122,31 @@ describe GitlabSchema do
     end
   end
 
+  describe '.object_from_id_when_present' do
+    context 'when the input is nil' do
+      it 'returns nil' do
+        expect(described_class.object_from_id_when_present(nil)).to be_nil
+      end
+    end
+
+    context 'when the input is an empty string' do
+      it 'returns nil' do
+        expect(described_class.object_from_id_when_present('')).to be_nil
+      end
+    end
+
+    context 'when the object is not nil' do
+      it 'behaves as object_from_id' do
+        user = create(:user)
+        gid = user.to_global_id.to_s
+
+        result = described_class.object_from_id_when_present(gid).__sync
+
+        expect(result).to eq(described_class.object_from_id(gid).__sync)
+      end
+    end
+  end
+
   describe '.object_from_id' do
     context 'for subclasses of `ApplicationRecord`' do
       it 'returns the correct record' do