GithubImporter: Expose import stats on import status endpoint

doc/api/project_import_export.md

@@ -294,6 +294,7 @@ The `failed_relations` array is capped to 100 items.
   "path_with_namespace": "gitlab-org/gitlab-test",
   "created_at": "2017-08-29T04:36:44.383Z",
   "import_status": "started",
+  "import_type": "github",
   "correlation_id": "mezklWso3Za",
   "failed_relations": [
     {
@@ -302,8 +303,58 @@ The `failed_relations` array is capped to 100 items.
       "exception_class": "RuntimeError",
       "exception_message": "A failure occurred",
       "source": "custom error context",
-      "relation_name": "merge_requests"
+      "relation_name": "merge_requests",
+      "line_number": 0
     }
   ]
 }
 ```
+
+When importing from GitHub, the a `stats` field lists how many objects were already fetched from
+GitHub and how many were already imported:
+
+```json
+{
+  "id": 1,
+  "description": "Itaque perspiciatis minima aspernatur corporis consequatur.",
+  "name": "Gitlab Test",
+  "name_with_namespace": "Gitlab Org / Gitlab Test",
+  "path": "gitlab-test",
+  "path_with_namespace": "gitlab-org/gitlab-test",
+  "created_at": "2017-08-29T04:36:44.383Z",
+  "import_status": "started",
+  "import_type": "github",
+  "correlation_id": "mezklWso3Za",
+  "failed_relations": [
+    {
+      "id": 42,
+      "created_at": "2020-04-02T14:48:59.526Z",
+      "exception_class": "RuntimeError",
+      "exception_message": "A failure occurred",
+      "source": "custom error context",
+      "relation_name": "merge_requests",
+      "line_number": 0
+    }
+  ],
+  "stats": {
+    "fetched": {
+      "diff_note": 19,
+      "issue": 3,
+      "label": 1,
+      "note": 3,
+      "pull_request": 2,
+      "pull_request_merged_by": 1,
+      "pull_request_review": 16
+    },
+    "imported": {
+      "diff_note": 19,
+      "issue": 3,
+      "label": 1,
+      "note": 3,
+      "pull_request": 2,
+      "pull_request_merged_by": 1,
+      "pull_request_review": 16
+    }
+  }
+}
+```

lib/api/entities/project_import_status.rb

@@ -16,6 +16,12 @@ module API
       expose :import_error do |project, _options|
         project.import_state&.last_error
       end
+
+      expose :stats do |project, _options|
+        if project.github_import?
+          ::Gitlab::GithubImport::ObjectCounter.summary(project)
+        end
+      end
     end
   end
 end

spec/lib/api/entities/project_import_status_spec.rb

@@ -17,6 +17,7 @@ RSpec.describe API::Entities::ProjectImportStatus, :aggregate_failures do
         expect(subject[:correlation_id]).to be_nil
         expect(subject[:import_error]).to be_nil
         expect(subject[:failed_relations]).to eq([])
+        expect(subject[:stats]).to be_nil
       end
     end
 
@@ -76,5 +77,22 @@ RSpec.describe API::Entities::ProjectImportStatus, :aggregate_failures do
         expect(subject[:failed_relations]).to eq([])
       end
     end
+
+    context 'when importing from github', :clean_gitlab_redis_cache do
+      let(:project) { create(:project, :import_failed, import_type: 'github') }
+      let(:entity) { described_class.new(project) }
+
+      before do
+        ::Gitlab::GithubImport::ObjectCounter.increment(project, :issues, :fetched, value: 10)
+        ::Gitlab::GithubImport::ObjectCounter.increment(project, :issues, :imported, value: 8)
+      end
+
+      it 'exposes the import stats' do
+        expect(subject[:stats]).to eq(
+          'fetched' => { 'issues' => 10 },
+          'imported' => { 'issues' => 8 }
+        )
+      end
+    end
   end
 end