GitHub import: Handle nil published_at dates

GitHub releases will have a null `published_at` field if they are in
the draft state. If no date is available in the release, just fill
it in with today's date since our database schema requires this.

Closes https://gitlab.com/gitlab-org/gitlab/issues/33732

changelogs/unreleased/sh-github-import-handle-nil-dates.yml

+---
+title: 'GitHub import: Handle nil published_at dates'
+merge_request: 18355
+author:
+type: fixed

lib/gitlab/github_import/importer/releases_importer.rb

@@ -37,7 +37,8 @@ module Gitlab
             description: description_for(release),
             created_at: release.created_at,
             updated_at: release.created_at,
-            released_at: release.published_at,
+            # Draft releases will have a null published_at
+            released_at: release.published_at || Time.current,
             project_id: project.id
           }
         end

lib/gitlab/legacy_github_import/release_formatter.rb

@@ -10,7 +10,8 @@ module Gitlab
           name: raw_data.name,
           description: raw_data.body,
           created_at: raw_data.created_at,
-          released_at: raw_data.published_at,
+          # Draft releases will have a null published_at
+          released_at: raw_data.published_at || Time.current,
           updated_at: raw_data.created_at
         }
       end

spec/lib/gitlab/github_import/importer/releases_importer_spec.rb

@@ -34,6 +34,22 @@ describe Gitlab::GithubImport::Importer::ReleasesImporter do
 
       importer.execute
     end
+
+    it 'imports draft releases' do
+      release_double = double(
+        name: 'Test',
+        body: 'This is description',
+        tag_name: '1.0',
+        description: 'This is my release',
+        created_at: created_at,
+        updated_at: created_at,
+        published_at: nil
+      )
+
+      expect(importer).to receive(:each_release).and_return([release_double])
+
+      expect { importer.execute }.to change { Release.count }.by(1)
+    end
   end
 
   describe '#build_releases' do

spec/lib/gitlab/legacy_github_import/release_formatter_spec.rb

@@ -37,6 +37,14 @@ describe Gitlab::LegacyGithubImport::ReleaseFormatter do
 
       expect(release.attributes).to eq(expected)
     end
+
+    context 'with a nil published_at date' do
+      let(:published_at) { nil }
+
+      it 'inserts a timestamp for released_at' do
+        expect(release.attributes[:released_at]).to be_a(Time)
+      end
+    end
   end
 
   describe '#valid' do