API: Return 404 if the tag for a release does not exist

app/services/create_release_service.rb

+require_relative 'base_service'
+
+class CreateReleaseService < BaseService
+  def execute(tag_name, release_description)
+
+    repository = project.repository
+    existing_tag = repository.find_tag(tag_name)
+
+    # Only create a release if the tag exists
+    if existing_tag
+      release = project.releases.find_or_initialize_by(tag: tag_name)
+      release.update_attributes(description: release_description)
+
+      success(release)
+    else
+      error('Tag does not exist')
+    end
+  end
+
+  def success(release)
+    out = super()
+    out[:release] = release
+    out
+  end
+end

app/services/create_tag_service.rb

@@ -19,16 +19,16 @@ class CreateTagService < BaseService
     new_tag = repository.find_tag(tag_name)
 
     if new_tag
-      if release_description
-        release = project.releases.find_or_initialize_by(tag: tag_name)
-        release.update_attributes(description: release_description)
-      end
-
       push_data = create_push_data(project, current_user, new_tag)
       EventCreateService.new.push(project, current_user, push_data)
       project.execute_hooks(push_data.dup, :tag_push_hooks)
       project.execute_services(push_data.dup, :tag_push_hooks)
 
+      if release_description
+        CreateReleaseService.new(@project, @current_user).
+          execute(tag_name, release_description)
+      end
+
       success(new_tag)
     else
       error('Invalid reference name')

doc/api/tags.md

@@ -86,7 +86,8 @@ It returns 200 if the operation succeed. In case of an error,
 
 ## New release
 
-Add release notes to the existing git tag
+Add release notes to the existing git tag. It returns 200 if the release is
+created successfully. If the tag does not exist, 404 is returned.
 
 ```
 PUT /projects/:id/repository/tags/:tag_name/release

lib/api/tags.rb

@@ -51,10 +51,14 @@ module API
       put ':id/repository/tags/:tag_name/release', requirements: { tag_name: /.*/ } do
         authorize_push_project
         required_attributes! [:description]
-        release = user_project.releases.find_or_initialize_by(tag: params[:tag_name])
-        release.update_attributes(description: params[:description])
+        result = CreateReleaseService.new(user_project, current_user).
+          execute(params[:tag_name], params[:description])
 
-        present release, with: Entities::Release
+        if result[:status] == :success
+          present result[:release], with: Entities::Release
+        else
+          render_api_error!(result[:message], 404)
+        end
       end
     end
   end

spec/requests/api/tags_spec.rb

@@ -131,5 +131,13 @@ describe API::API, api: true  do
       expect(json_response['tag_name']).to eq(tag_name)
       expect(json_response['description']).to eq(description)
     end
+
+    it 'should return 404 if the tag does not exist' do
+      put api("/projects/#{project.id}/repository/tags/foobar/release", user),
+        description: description
+
+      expect(response.status).to eq(404)
+      expect(json_response['message']).to eq('Tag does not exist')
+    end
   end
 end