Specify failing dependencies in the callout message

To avoid unexpected side-effects elsewhere, we only
return the detailed message in the build details entity.
This is because we only want to show this message in the
job details page.

app/models/ci/build.rb

@@ -758,6 +758,10 @@ module Ci
       true
     end
 
+    def invalid_dependencies
+      dependencies.reject(&:valid_dependency?)
+    end
+
     def runner_required_feature_names
       strong_memoize(:runner_required_feature_names) do
         RUNNER_FEATURES.select do |feature, method|

app/serializers/build_details_entity.rb

@@ -121,4 +121,28 @@ class BuildDetailsEntity < JobEntity
   def can_admin_build?
     can?(request.current_user, :admin_build, project)
   end
+
+  def callout_message
+    return super unless build.failure_reason.to_sym == :missing_dependency_failure
+
+    docs_url = "https://docs.gitlab.com/ce/ci/yaml/README.html#when-a-dependent-job-will-fail"
+
+    [
+      failure_message.html_safe,
+      help_message(docs_url).html_safe
+    ].join("<br />")
+  end
+
+  def invalid_dependencies
+    build.invalid_dependencies.map(&:name).join(', ')
+  end
+
+  def failure_message
+    _("There were missing dependencies from the following job(s): %{invalid_dependencies}") %
+      { invalid_dependencies: invalid_dependencies }
+  end
+
+  def help_message(docs_url)
+    _("Please refer to <a href=\"%{docs_url}\">%{docs_url}</a>") % { docs_url: docs_url }
+  end
 end

changelogs/unreleased/eb-missing-dependencies-custom-callout-message.yml

+---
+title: Include in the callout message a list of jobs that caused missing dependencies
+  failure.
+merge_request: 18219
+author:
+type: added

spec/models/ci/build_spec.rb

@@ -3925,4 +3925,14 @@ describe Ci::Build do
       end
     end
   end
+
+  describe '#invalid_dependencies' do
+    let!(:pre_stage_job_valid) { create(:ci_build, :manual, pipeline: pipeline, name: 'test1', stage_idx: 0) }
+    let!(:pre_stage_job_invalid) { create(:ci_build, :success, :expired, pipeline: pipeline, name: 'test2', stage_idx: 1) }
+    let!(:job) { create(:ci_build, :pending, pipeline: pipeline, stage_idx: 2, options: { dependencies: %w(test1 test2) }) }
+
+    it 'returns invalid dependencies' do
+      expect(job.invalid_dependencies).to eq([pre_stage_job_invalid])
+    end
+  end
 end

spec/serializers/build_details_entity_spec.rb

@@ -123,6 +123,24 @@ describe BuildDetailsEntity do
       end
 
       it { is_expected.to include(failure_reason: 'unmet_prerequisites') }
+      it { is_expected.to include(callout_message: CommitStatusPresenter.callout_failure_messages[:unmet_prerequisites]) }
+    end
+
+    context 'when the build has failed due to a missing dependency' do
+      let!(:test1) { create(:ci_build, :success, :expired, pipeline: pipeline, name: 'test1', stage_idx: 0) }
+      let!(:test2) { create(:ci_build, :success, :expired, pipeline: pipeline, name: 'test2', stage_idx: 1) }
+      let!(:build) { create(:ci_build, :pending, pipeline: pipeline, stage_idx: 2, options: { dependencies: %w(test1 test2) }) }
+      let(:message) { subject[:callout_message] }
+
+      before do
+        build.drop!(:missing_dependency_failure)
+      end
+
+      it { is_expected.to include(failure_reason: 'missing_dependency_failure') }
+
+      it 'includes the failing dependencies in the callout message' do
+        expect(message).to include('test2, test1')
+      end
     end
 
     context 'when a build has environment with latest deployment' do