Fix import/export not checking upload result

Previously if a project export were not saved or uploaded,
a user would receive notification that the export was successful.

We now check the return result of the service and notify the
user properly.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/349425

Changelog: fixed

app/services/projects/import_export/export_service.rb

@@ -47,8 +47,7 @@ module Projects
       end
 
       def save_all!
-        if save_exporters
-          Gitlab::ImportExport::Saver.save(exportable: project, shared: shared)
+        if save_exporters && save_export_archive
           notify_success
         else
           notify_error!
@@ -59,6 +58,10 @@ module Projects
         exporters.all?(&:save)
       end
 
+      def save_export_archive
+        Gitlab::ImportExport::Saver.save(exportable: project, shared: shared)
+      end
+
       def exporters
         [
           version_saver, avatar_saver, project_tree_saver, uploads_saver,

ee/spec/services/projects/import_export/export_service_spec.rb

@@ -20,7 +20,7 @@ RSpec.describe Projects::ImportExport::ExportService do
         end
 
         it 'succeeds' do
-          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project_template, shared: shared)
+          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project_template, shared: shared).and_return(true)
 
           subject
         end
@@ -32,7 +32,7 @@ RSpec.describe Projects::ImportExport::ExportService do
         end
 
         it 'succeeds' do
-          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project_template, shared: shared)
+          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project_template, shared: shared).and_return(true)
 
           subject
         end

lib/gitlab/import_export/saver.rb

@@ -54,6 +54,8 @@ module Gitlab
         File.open(archive_file) { |file| upload.export_file = file }
 
         upload.save!
+
+        true
       end
 
       def error_message

spec/services/projects/import_export/export_service_spec.rb

@@ -93,11 +93,23 @@ RSpec.describe Projects::ImportExport::ExportService do
       end
 
       it 'saves the project in the file system' do
-        expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project, shared: shared)
+        expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project, shared: shared).and_return(true)
 
         service.execute
       end
 
+      context 'when the upload fails' do
+        before do
+          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project, shared: shared).and_return(false)
+        end
+
+        it 'notifies the user of an error' do
+          expect(service).to receive(:notify_error).and_call_original
+
+          expect { service.execute }.to raise_error(Gitlab::ImportExport::Error)
+        end
+      end
+
       it 'calls the after export strategy' do
         expect(after_export_strategy).to receive(:execute)
 
@@ -107,6 +119,7 @@ RSpec.describe Projects::ImportExport::ExportService do
       context 'when after export strategy fails' do
         before do
           allow(after_export_strategy).to receive(:execute).and_return(false)
+          expect(Gitlab::ImportExport::Saver).to receive(:save).with(exportable: project, shared: shared).and_return(true)
         end
 
         after do