Implement prefilled variables backend for run pipeline

This is just a backend work for the feature.
This introduces a new endpoint to provide defined variables
in CI config file.

app/controllers/projects/pipelines_controller.rb

@@ -5,11 +5,11 @@ class Projects::PipelinesController < Projects::ApplicationController
   include Analytics::UniqueVisitsHelper
 
   before_action :whitelist_query_limiting, only: [:create, :retry]
-  before_action :pipeline, except: [:index, :new, :create, :charts]
+  before_action :pipeline, except: [:index, :new, :create, :charts, :config_variables]
   before_action :set_pipeline_path, only: [:show]
   before_action :authorize_read_pipeline!
   before_action :authorize_read_build!, only: [:index]
-  before_action :authorize_create_pipeline!, only: [:new, :create]
+  before_action :authorize_create_pipeline!, only: [:new, :create, :config_variables]
   before_action :authorize_update_pipeline!, only: [:retry, :cancel]
   before_action do
     push_frontend_feature_flag(:filter_pipelines_search, project, default_enabled: true)
@@ -209,6 +209,14 @@ class Projects::PipelinesController < Projects::ApplicationController
     end
   end
 
+  def config_variables
+    respond_to do |format|
+      format.json do
+        render json: Ci::ListConfigVariablesService.new(@project).execute(params[:sha])
+      end
+    end
+  end
+
   private
 
   def serialize_pipelines

app/models/project.rb

@@ -2514,6 +2514,10 @@ class Project < ApplicationRecord
     ci_config_path.presence || Ci::Pipeline::DEFAULT_CONFIG_PATH
   end
 
+  def ci_config_for(sha)
+    repository.gitlab_ci_yml_for(sha, ci_config_path_or_default)
+  end
+
   def enabled_group_deploy_keys
     return GroupDeployKey.none unless group
 

app/services/ci/list_config_variables_service.rb

+# frozen_string_literal: true
+
+module Ci
+  class ListConfigVariablesService < ::BaseService
+    def execute(sha)
+      config = project.ci_config_for(sha)
+      return {} unless config
+
+      result = Gitlab::Ci::YamlProcessor.new(config).execute
+      result.valid? ? result.variables_with_data : {}
+    end
+  end
+end

config/routes/pipelines.rb

@@ -7,6 +7,7 @@ resources :pipelines, only: [:index, :new, :create, :show, :destroy] do
     scope '(*ref)', constraints: { ref: Gitlab::PathRegex.git_reference_regex } do
       get :latest, action: :show, defaults: { latest: true }
     end
+    get :config_variables
   end
 
   member do

lib/gitlab/ci/config.rb

@@ -54,6 +54,10 @@ module Gitlab
         root.variables_value
       end
 
+      def variables_with_data
+        root.variables_entry.value_with_data
+      end
+
       def stages
         root.stages_value
       end

lib/gitlab/ci/config/entry/variables.rb

@@ -10,16 +10,32 @@ module Gitlab
         class Variables < ::Gitlab::Config::Entry::Node
           include ::Gitlab::Config::Entry::Validatable
 
+          ALLOWED_VALUE_DATA = %i[value description].freeze
+
           validations do
-            validates :config, variables: true
+            validates :config, variables: { allowed_value_data: ALLOWED_VALUE_DATA }
+          end
+
+          def value
+            Hash[@config.map { |key, value| [key.to_s, expand_value(value)[:value]] }]
           end
 
           def self.default(**)
             {}
           end
 
-          def value
-            Hash[@config.map { |key, value| [key.to_s, value.to_s] }]
+          def value_with_data
+            Hash[@config.map { |key, value| [key.to_s, expand_value(value)] }]
+          end
+
+          private
+
+          def expand_value(value)
+            if value.is_a?(Hash)
+              { value: value[:value].to_s, description: value[:description] }
+            else
+              { value: value.to_s, description: nil }
+            end
           end
         end
       end

lib/gitlab/ci/yaml_processor/result.rb

@@ -99,6 +99,10 @@ module Gitlab
           @ci_config&.to_hash&.to_yaml
         end
 
+        def variables_with_data
+          @ci_config.variables_with_data
+        end
+
         private
 
         def variables

lib/gitlab/config/entry/legacy_validation_helpers.rb

@@ -50,6 +50,12 @@ module Gitlab
             variables.values.flatten(1).all?(&method(:validate_alphanumeric))
         end
 
+        def validate_string_or_hash_value_variables(variables, allowed_value_data)
+          variables.is_a?(Hash) &&
+            variables.keys.all?(&method(:validate_alphanumeric)) &&
+            variables.values.all? { |value| validate_string_or_hash_value_variable(value, allowed_value_data) }
+        end
+
         def validate_alphanumeric(value)
           validate_string(value) || validate_integer(value)
         end
@@ -62,6 +68,14 @@ module Gitlab
           value.is_a?(String) || value.is_a?(Symbol)
         end
 
+        def validate_string_or_hash_value_variable(value, allowed_value_data)
+          if value.is_a?(Hash)
+            (value.keys - allowed_value_data).empty? && value.values.all?(&method(:validate_alphanumeric))
+          else
+            validate_alphanumeric(value)
+          end
+        end
+
         def validate_regexp(value)
           Gitlab::UntrustedRegexp::RubySyntax.valid?(value)
         end

lib/gitlab/config/entry/validators.rb

@@ -274,6 +274,8 @@ module Gitlab
           def validate_each(record, attribute, value)
             if options[:array_values]
               validate_key_array_values(record, attribute, value)
+            elsif options[:allowed_value_data]
+              validate_key_hash_values(record, attribute, value, options[:allowed_value_data])
             else
               validate_key_values(record, attribute, value)
             end
@@ -290,6 +292,12 @@ module Gitlab
               record.errors.add(attribute, 'should be a hash of key value pairs, value can be an array')
             end
           end
+
+          def validate_key_hash_values(record, attribute, value, allowed_value_data)
+            unless validate_string_or_hash_value_variables(value, allowed_value_data)
+              record.errors.add(attribute, 'should be a hash of key value pairs, value can be a hash')
+            end
+          end
         end
 
         class ExpressionValidator < ActiveModel::EachValidator

spec/controllers/projects/pipelines_controller_spec.rb

@@ -1148,4 +1148,84 @@ RSpec.describe Projects::PipelinesController do
                        }
     end
   end
+
+  describe 'GET config_variables.json' do
+    let(:result) { YAML.dump(ci_config) }
+
+    before do
+      stub_gitlab_ci_yml_for_sha(sha, result)
+    end
+
+    context 'when sending a valid sha' do
+      let(:sha) { 'master' }
+      let(:ci_config) do
+        {
+          variables: {
+            KEY1: { value: 'val 1', description: 'description 1' }
+          },
+          test: {
+            stage: 'test',
+            script: 'echo'
+          }
+        }
+      end
+
+      it 'returns variable list' do
+        get_config_variables
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response['KEY1']).to eq({ 'value' => 'val 1', 'description' => 'description 1' })
+      end
+    end
+
+    context 'when sending an invalid sha' do
+      let(:sha) { 'invalid-sha' }
+      let(:ci_config) { nil }
+
+      it 'returns empty json' do
+        get_config_variables
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response).to eq({})
+      end
+    end
+
+    context 'when sending an invalid config' do
+      let(:sha) { 'master' }
+      let(:ci_config) do
+        {
+          variables: {
+            KEY1: { value: 'val 1', description: 'description 1' }
+          },
+          test: {
+            stage: 'invalid',
+            script: 'echo'
+          }
+        }
+      end
+
+      it 'returns empty result' do
+        get_config_variables
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response).to eq({})
+      end
+    end
+
+    private
+
+    def stub_gitlab_ci_yml_for_sha(sha, result)
+      allow_any_instance_of(Repository)
+          .to receive(:gitlab_ci_yml_for)
+          .with(sha, '.gitlab-ci.yml')
+          .and_return(result)
+    end
+
+    def get_config_variables
+      get :config_variables, params: { namespace_id: project.namespace,
+                                       project_id: project,
+                                       sha: sha },
+                             format: :json
+    end
+  end
 end

spec/lib/gitlab/ci/config/entry/variables_spec.rb

@@ -3,56 +3,109 @@
 require 'spec_helper'
 
 RSpec.describe Gitlab::Ci::Config::Entry::Variables do
-  let(:entry) { described_class.new(config) }
-
-  describe 'validations' do
-    context 'when entry config value is correct' do
-      let(:config) do
-        { 'VARIABLE_1' => 'value 1', 'VARIABLE_2' => 'value 2' }
-      end
+  subject { described_class.new(config) }
 
+  shared_examples 'valid config' do
     describe '#value' do
       it 'returns hash with key value strings' do
-          expect(entry.value).to eq config
-        end
-
-        context 'with numeric keys and values in the config' do
-          let(:config) { { 10 => 20 } }
-
-          it 'converts numeric key and numeric value into strings' do
-            expect(entry.value).to eq('10' => '20')
-          end
+        expect(subject.value).to eq result
       end
     end
 
     describe '#errors' do
       it 'does not append errors' do
-          expect(entry.errors).to be_empty
+        expect(subject.errors).to be_empty
       end
     end
 
     describe '#valid?' do
       it 'is valid' do
-          expect(entry).to be_valid
+        expect(subject).to be_valid
       end
     end
   end
 
-    context 'when entry value is not correct' do
-      let(:config) { [:VAR, 'test'] }
+  shared_examples 'invalid config' do
+    describe '#valid?' do
+      it 'is not valid' do
+        expect(subject).not_to be_valid
+      end
+    end
 
     describe '#errors' do
       it 'saves errors' do
-          expect(entry.errors)
+        expect(subject.errors)
           .to include /should be a hash of key value pairs/
       end
     end
+  end
 
-      describe '#valid?' do
-        it 'is not valid' do
-          expect(entry).not_to be_valid
+  context 'when entry config value has key-value pairs' do
+    let(:config) do
+      { 'VARIABLE_1' => 'value 1', 'VARIABLE_2' => 'value 2' }
+    end
+
+    let(:result) do
+      { 'VARIABLE_1' => 'value 1', 'VARIABLE_2' => 'value 2' }
     end
+
+    it_behaves_like 'valid config'
   end
+
+  context 'with numeric keys and values in the config' do
+    let(:config) { { 10 => 20 } }
+    let(:result) do
+      { '10' => '20' }
+    end
+
+    it_behaves_like 'valid config'
   end
+
+  context 'when entry config value has key-value pair and hash' do
+    let(:config) do
+      { 'VARIABLE_1' => { value: 'value 1', description: 'variable 1' },
+        'VARIABLE_2' => 'value 2' }
+    end
+
+    let(:result) do
+      { 'VARIABLE_1' => 'value 1', 'VARIABLE_2' => 'value 2' }
+    end
+
+    it_behaves_like 'valid config'
+  end
+
+  context 'when entry value is an array' do
+    let(:config) { [:VAR, 'test'] }
+
+    it_behaves_like 'invalid config'
+  end
+
+  context 'when entry value has hash with other key-pairs' do
+    let(:config) do
+      { 'VARIABLE_1' => { value: 'value 1', hello: 'variable 1' },
+        'VARIABLE_2' => 'value 2' }
+    end
+
+    it_behaves_like 'invalid config'
+  end
+
+  context 'when entry config value has hash with nil description' do
+    let(:config) do
+      { 'VARIABLE_1' => { value: 'value 1', description: nil } }
+    end
+
+    it_behaves_like 'invalid config'
+  end
+
+  context 'when entry config value has hash without description' do
+    let(:config) do
+      { 'VARIABLE_1' => { value: 'value 1' } }
+    end
+
+    let(:result) do
+      { 'VARIABLE_1' => 'value 1' }
+    end
+
+    it_behaves_like 'valid config'
   end
 end

spec/lib/gitlab/ci/yaml_processor_spec.rb

@@ -2465,13 +2465,13 @@ module Gitlab
         context 'returns errors if variables is not a map' do
           let(:config) { YAML.dump({ variables: "test", rspec: { script: "test" } }) }
 
-          it_behaves_like 'returns errors', 'variables config should be a hash of key value pairs'
+          it_behaves_like 'returns errors', 'variables config should be a hash of key value pairs, value can be a hash'
         end
 
         context 'returns errors if variables is not a map of key-value strings' do
           let(:config) { YAML.dump({ variables: { test: false }, rspec: { script: "test" } }) }
 
-          it_behaves_like 'returns errors', 'variables config should be a hash of key value pairs'
+          it_behaves_like 'returns errors', 'variables config should be a hash of key value pairs, value can be a hash'
         end
 
         context 'returns errors if job when is not on_success, on_failure or always' do

spec/services/ci/list_config_variables_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Ci::ListConfigVariablesService do
+  let_it_be(:project) { create(:project, :repository) }
+  let(:service) { described_class.new(project) }
+  let(:result) { YAML.dump(ci_config) }
+
+  subject { service.execute(sha) }
+
+  before do
+    stub_gitlab_ci_yml_for_sha(sha, result)
+  end
+
+  context 'when sending a valid sha' do
+    let(:sha) { 'master' }
+    let(:ci_config) do
+      {
+        variables: {
+          KEY1: { value: 'val 1', description: 'description 1' },
+          KEY2: { value: 'val 2', description: '' },
+          KEY3: { value: 'val 3' },
+          KEY4: 'val 4'
+        },
+        test: {
+          stage: 'test',
+          script: 'echo'
+        }
+      }
+    end
+
+    it 'returns variable list' do
+      expect(subject['KEY1']).to eq({ value: 'val 1', description: 'description 1' })
+      expect(subject['KEY2']).to eq({ value: 'val 2', description: '' })
+      expect(subject['KEY3']).to eq({ value: 'val 3', description: nil })
+      expect(subject['KEY4']).to eq({ value: 'val 4', description: nil })
+    end
+  end
+
+  context 'when sending an invalid sha' do
+    let(:sha) { 'invalid-sha' }
+    let(:ci_config) { nil }
+
+    it 'returns empty json' do
+      expect(subject).to eq({})
+    end
+  end
+
+  context 'when sending an invalid config' do
+    let(:sha) { 'master' }
+    let(:ci_config) do
+      {
+        variables: {
+          KEY1: { value: 'val 1', description: 'description 1' }
+        },
+        test: {
+          stage: 'invalid',
+          script: 'echo'
+        }
+      }
+    end
+
+    it 'returns empty result' do
+      expect(subject).to eq({})
+    end
+  end
+
+  private
+
+  def stub_gitlab_ci_yml_for_sha(sha, result)
+    allow_any_instance_of(Repository)
+        .to receive(:gitlab_ci_yml_for)
+        .with(sha, '.gitlab-ci.yml')
+        .and_return(result)
+  end
+end