Fix bug when exposing non existing artifacts

When `expose_as` is used and no artifacts have been
uploaded it raises an unexpected error.

app/services/ci/find_exposed_artifacts_service.rb

@@ -46,6 +46,8 @@ module Ci
     # it could contain many. We only need to know whether it has 1 or more
     # artifacts, so fetching the first 2 would be sufficient.
     def first_2_metadata_entries_for_artifacts_paths(job)
+      return [] unless job.artifacts_metadata
+
       job.artifacts_paths
         .lazy
         .map { |path| job.artifacts_metadata_entry(path, recursive: true) }

changelogs/unreleased/fix-no-artifacts-when-exposed.yml

+---
+title: Fix bug when trying to expose artifacts and no artifacts are produced by the job
+merge_request: 22378
+author:
+type: fixed

spec/services/ci/find_exposed_artifacts_service_spec.rb

@@ -50,10 +50,39 @@ describe Ci::FindExposedArtifactsService do
       end
     end
 
+    shared_examples 'does not find any matches' do
+      it 'returns empty array' do
+        expect(subject).to eq []
+      end
+    end
+
     let_it_be(:pipeline) { create(:ci_pipeline, project: project) }
 
     subject { described_class.new(project, user).for_pipeline(pipeline) }
 
+    context 'with jobs having no exposed artifacts' do
+      let!(:job) do
+        create_job_with_artifacts(artifacts: {
+          paths: ['other_artifacts_0.1.2/doc_sample.txt', 'something-else.html']
+        })
+      end
+
+      it_behaves_like 'does not find any matches'
+    end
+
+    context 'with jobs having no artifacts (metadata)' do
+      let!(:job) do
+        create(:ci_build, pipeline: pipeline, options: {
+          artifacts: {
+            expose_as: 'Exposed artifact',
+            paths: ['other_artifacts_0.1.2/doc_sample.txt', 'something-else.html']
+          }
+        })
+      end
+
+      it_behaves_like 'does not find any matches'
+    end
+
     context 'with jobs having at most 1 matching exposed artifact' do
       let!(:job) do
         create_job_with_artifacts(artifacts: {