Enable to delete a value stream

But only if it is not default value stream
Expose is_custom field on value stream

ee/app/controllers/groups/analytics/cycle_analytics/value_streams_controller.rb

@@ -24,6 +24,17 @@ class Groups::Analytics::CycleAnalytics::ValueStreamsController < Analytics::App
     end
   end
 
+  def destroy
+    value_stream = @group.value_streams.find(params[:id])
+
+    if value_stream.custom?
+      value_stream.delete
+      render json: {}, status: :ok
+    else
+      render json: { message: s_('ValueStream|The Default Value Stream cannot be deleted') }, status: :unprocessable_entity
+    end
+  end
+
   private
 
   def value_stream_params

ee/app/models/analytics/cycle_analytics/group_value_stream.rb

@@ -7,4 +7,8 @@ class Analytics::CycleAnalytics::GroupValueStream < ApplicationRecord
 
   validates :group, :name, presence: true
   validates :name, length: { minimum: 3, maximum: 100, allow_nil: false }, uniqueness: { scope: :group_id }
+
+  def custom?
+    name != Analytics::CycleAnalytics::Stages::BaseService::DEFAULT_VALUE_STREAM_NAME
+  end
 end

ee/app/serializers/analytics/cycle_analytics/group_value_stream_entity.rb

@@ -4,6 +4,9 @@ module Analytics
   class GroupValueStreamEntity < Grape::Entity
     expose :name
     expose :id
+    expose :is_custom do |object|
+      object.custom?
+    end
 
     private
 

ee/changelogs/unreleased/delete-custom-value-stream.yml

+---
+title: Enable to delete a custom value stream
+merge_request: 40127
+author:
+type: added

ee/config/routes/group.rb

@@ -39,7 +39,7 @@ constraints(::Constraints::GroupUrlConstrainer.new) do
               get :records
             end
           end
-          resources :value_streams, only: [:index, :create] do
+          resources :value_streams, only: [:index, :create, :destroy] do
             resources :stages, only: [:index, :create, :update, :destroy] do
               member do
                 get :duration_chart

ee/spec/controllers/groups/analytics/cycle_analytics/value_streams_controller_spec.rb

@@ -62,4 +62,33 @@ RSpec.describe Groups::Analytics::CycleAnalytics::ValueStreamsController do
       end
     end
   end
+
+  describe 'DELETE #destroy' do
+    def destroy_value_stream
+      delete :destroy, params: { group_id: group, id: value_stream }
+    end
+
+    context 'when it is a default value stream' do
+      let!(:value_stream) { create(:cycle_analytics_group_value_stream, group: group, name: 'default') }
+
+      it 'returns an unprocessable entity 422 response without deleting the value stream' do
+        expect { destroy_value_stream }.not_to change { Analytics::CycleAnalytics::GroupValueStream.count }
+
+        expect(response).to have_gitlab_http_status(:unprocessable_entity)
+        expect(json_response["message"]).to eq('The Default Value Stream cannot be deleted')
+      end
+    end
+
+    context 'when it is a custom value stream' do
+      let!(:value_stream) { create(:cycle_analytics_group_value_stream, group: group, name: 'some custom value stream') }
+      let!(:stage) { create(:cycle_analytics_group_stage, value_stream: value_stream) }
+
+      it 'deletes the value stream and its stages, and returns a successful 200 response' do
+        expect { destroy_value_stream }.to change { Analytics::CycleAnalytics::GroupValueStream.count }.by(-1)
+          .and change { Analytics::CycleAnalytics::GroupStage.where(value_stream: value_stream).count }.from(1).to(0)
+
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+    end
+  end
 end

ee/spec/fixtures/api/schemas/analytics/cycle_analytics/value_stream.json

 {
   "type": "object",
-  "required": ["name", "id"],
+  "required": ["name", "id", "is_custom"],
   "properties": {
     "id": {
       "type": ["integer", "string"]
     },
     "name": {
       "type": "string"
+    },
+    "is_custom": {
+      "type": "boolean"
     }
   },
   "additionalProperties": false

locale/gitlab.pot

@@ -27066,6 +27066,9 @@ msgstr ""
 msgid "ValueStreamAnalytics|Median time from issue created to issue closed."
 msgstr ""
 
+msgid "ValueStream|The Default Value Stream cannot be deleted"
+msgstr ""
+
 msgid "Variable"
 msgstr ""