Fix invalid pipeline build chain tag evaluation

lib/gitlab/ci/pipeline/chain/build.rb

@@ -3,8 +3,6 @@ module Gitlab
     module Pipeline
       module Chain
         class Build < Chain::Base
-          include Chain::Helpers
-
           def perform!
             @pipeline.assign_attributes(
               source: @command.source,
@@ -51,6 +49,10 @@ module Gitlab
           def protected_ref?
             @project.protected_for?(ref)
           end
+
+          def tag_exists?
+            project.repository.tag_exists?(ref)
+          end
         end
       end
     end

lib/gitlab/ci/pipeline/chain/helpers.rb

@@ -3,16 +3,22 @@ module Gitlab
     module Pipeline
       module Chain
         module Helpers
+          include Gitlab::Utils::StrongMemoize
+
           def branch_exists?
-            return @is_branch if defined?(@is_branch)
+            strong_memoize(:is_branch) do
+              raise ArgumentError unless pipeline.ref
 
-            @is_branch = project.repository.branch_exists?(pipeline.ref)
+              project.repository.branch_exists?(pipeline.ref)
+            end
           end
 
           def tag_exists?
-            return @is_tag if defined?(@is_tag)
+            strong_memoize(:is_tag) do
+              raise ArgumentError unless pipeline.ref
 
-            @is_tag = project.repository.tag_exists?(pipeline.ref)
+              project.repository.tag_exists?(pipeline.ref)
+            end
           end
 
           def error(message)

spec/lib/gitlab/ci/pipeline/chain/build_spec.rb

@@ -21,31 +21,64 @@ describe Gitlab::Ci::Pipeline::Chain::Build do
 
   before do
     stub_repository_ci_yaml_file(sha: anything)
-
-    step.perform!
   end
 
   it 'never breaks the chain' do
+    step.perform!
+
     expect(step.break?).to be false
   end
 
   it 'fills pipeline object with data' do
+    step.perform!
+
     expect(pipeline.sha).not_to be_empty
     expect(pipeline.sha).to eq project.commit.id
     expect(pipeline.ref).to eq 'master'
+    expect(pipeline.tag).to be false
     expect(pipeline.user).to eq user
     expect(pipeline.project).to eq project
   end
 
   it 'sets a valid config source' do
+    step.perform!
+
     expect(pipeline.repository_source?).to be true
   end
 
   it 'returns a valid pipeline' do
+    step.perform!
+
     expect(pipeline).to be_valid
   end
 
   it 'does not persist a pipeline' do
+    step.perform!
+
     expect(pipeline).not_to be_persisted
   end
+
+  context 'when pipeline is running for a tag' do
+    let(:command) do
+      double('command', source: :push,
+                        origin_ref: 'mytag',
+                        checkout_sha: project.commit.id,
+                        after_sha: nil,
+                        before_sha: nil,
+                        trigger_request: nil,
+                        schedule: nil,
+                        project: project,
+                        current_user: user)
+    end
+
+    before do
+      allow(step).to receive(:tag_exists?).and_return(true)
+
+      step.perform!
+    end
+
+    it 'correctly indicated that this is a tagged pipeline' do
+      expect(pipeline).to be_tag
+    end
+  end
 end

spec/services/ci/create_pipeline_service_spec.rb

@@ -518,5 +518,25 @@ describe Ci::CreatePipelineService do
         end
       end
     end
+
+    context 'when pipelie is running for a tag' do
+      before do
+        allow_any_instance_of(Repository)
+          .to receive(:tag_exists?).and_return(false)
+        allow_any_instance_of(Repository)
+          .to receive(:tag_exists?).with('refs/tags/mytag').and_return(true)
+
+        config = YAML.dump(test: { script: 'test', only: ['branches'] },
+                                   deploy: { script: 'deploy', only: ['tags'] })
+
+        stub_ci_pipeline_yaml_file(config)
+      end
+
+      it 'creates a tagged pipeline' do
+        pipeline = execute_service(ref: 'mytag')
+
+        expect(pipeline.tag?).to be true
+      end
+    end
   end
 end