Switch errors to inherit from a base class

Error classes associated with individual stages of
dashboard processing tend to have very long names.
As dashboard post-processing includes more steps,
we will likely need to handle more error cases.
Refactoring to have all errors inherit from a specific
base class will help accommodate this and keep the code
more readable.

lib/gitlab/metrics/dashboard/base_service.rb

@@ -6,14 +6,13 @@ module Gitlab
   module Metrics
     module Dashboard
       class BaseService < ::BaseService
-        DASHBOARD_LAYOUT_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardLayoutError
-        MISSING_QUERY_ERROR = Gitlab::Metrics::Dashboard::Stages::EndpointInserter::MissingQueryError
+        PROCESSING_ERROR = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
 
         def get_dashboard
           return error("#{dashboard_path} could not be found.", :not_found) unless path_available?
 
           success(dashboard: process_dashboard)
-        rescue DASHBOARD_LAYOUT_ERROR, MISSING_QUERY_ERROR => e
+        rescue PROCESSING_ERROR => e
           error(e.message, :unprocessable_entity)
         end
 

lib/gitlab/metrics/dashboard/stages/base_stage.rb

@@ -5,7 +5,8 @@ module Gitlab
     module Dashboard
       module Stages
         class BaseStage
-          DashboardLayoutError = Class.new(StandardError)
+          DashboardProcessingError = Class.new(StandardError)
+          LayoutError = Class.new(DashboardProcessingError)
 
           DEFAULT_PANEL_TYPE = 'area-chart'
 
@@ -25,15 +26,15 @@ module Gitlab
           protected
 
           def missing_panel_groups!
-            raise DashboardLayoutError.new('Top-level key :panel_groups must be an array')
+            raise LayoutError.new('Top-level key :panel_groups must be an array')
           end
 
           def missing_panels!
-            raise DashboardLayoutError.new('Each "panel_group" must define an array :panels')
+            raise LayoutError.new('Each "panel_group" must define an array :panels')
           end
 
           def missing_metrics!
-            raise DashboardLayoutError.new('Each "panel" must define an array :metrics')
+            raise LayoutError.new('Each "panel" must define an array :metrics')
           end
 
           def for_metrics

lib/gitlab/metrics/dashboard/stages/endpoint_inserter.rb

@@ -5,7 +5,7 @@ module Gitlab
     module Dashboard
       module Stages
         class EndpointInserter < BaseStage
-          MissingQueryError = Class.new(StandardError)
+          MissingQueryError = Class.new(DashboardProcessingError)
 
           def transform!
             for_metrics do |metric|
@@ -31,7 +31,7 @@ module Gitlab
           def query_for_metric(metric)
             query = metric[query_type(metric)]
 
-            raise MissingQueryError.new('Missing required metric key: one of :query or :query_range') unless query
+            raise MissingQueryError.new('Each "metric" must define one of :query or :query_range') unless query
 
             query
           end

spec/lib/gitlab/metrics/dashboard/finder_spec.rb

@@ -28,12 +28,8 @@ describe Gitlab::Metrics::Dashboard::Finder, :use_clean_rails_memory_store_cachi
     end
 
     context 'when the dashboard contains a metric without a query' do
-      let(:project) do
-        project_with_dashboard(
-          dashboard_path,
-          { 'panel_groups' => [{ 'panels' => [{ 'metrics' => [{ 'id' => 'mock' }] }] }] }.to_yaml
-        )
-      end
+      let(:dashboard) { { 'panel_groups' => [{ 'panels' => [{ 'metrics' => [{ 'id' => 'mock' }] }] }] } }
+      let(:project) { project_with_dashboard(dashboard_path, dashboard.to_yaml) }
 
       it_behaves_like 'misconfigured dashboard service response', :unprocessable_entity
     end

spec/lib/gitlab/metrics/dashboard/processor_spec.rb

@@ -11,14 +11,11 @@ describe Gitlab::Metrics::Dashboard::Processor do
     let(:process_params) { [project, environment, dashboard_yml] }
     let(:dashboard) { described_class.new(*process_params).process(insert_project_metrics: true) }
 
-    # rubocop:disable RSpec/IteratedExpectation
-    # Cop disabled "all" matcher doesn't offer access to the element
     it 'includes a path for the prometheus endpoint with each metric' do
-      all_metrics.each do |metric|
-        expect(metric).to include(prometheus_endpoint_path: prometheus_path(metric[:query_range]))
+      expect(all_metrics).to satisfy_all do |metric|
+        metric[:prometheus_endpoint_path] == prometheus_path(metric[:query_range])
       end
     end
-    # rubocop:enable RSpec/IteratedExpectation
 
     context 'when dashboard config corresponds to common metrics' do
       let!(:common_metric) { create(:prometheus_metric, :common, identifier: 'metric_a1') }
@@ -70,7 +67,7 @@ describe Gitlab::Metrics::Dashboard::Processor do
 
     shared_examples_for 'errors with message' do |expected_message|
       it 'raises a DashboardLayoutError' do
-        error_class = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardLayoutError
+        error_class = Gitlab::Metrics::Dashboard::Stages::BaseStage::DashboardProcessingError
 
         expect { dashboard }.to raise_error(error_class, expected_message)
       end
@@ -93,6 +90,12 @@ describe Gitlab::Metrics::Dashboard::Processor do
 
       it_behaves_like 'errors with message', 'Each "panel" must define an array :metrics'
     end
+
+    context 'when the dashboard contains a metric which is missing a query' do
+      let(:dashboard_yml) { { panel_groups: [{ panels: [{ metrics: [{}] }] }] } }
+
+      it_behaves_like 'errors with message', 'Each "metric" must define one of :query or :query_range'
+    end
   end
 
   private
@@ -114,9 +117,11 @@ describe Gitlab::Metrics::Dashboard::Processor do
   end
 
   def prometheus_path(query)
-    "/#{project.namespace.path}" \
-    "/#{project.name}/environments/" \
-    "#{environment.id}/prometheus/api/v1" \
-    "/query_range?query=#{CGI.escape query}"
+    Gitlab::Routing.url_helpers.prometheus_api_project_environment_path(
+      project,
+      environment,
+      proxy_path: :query_range,
+      query: query
+    )
   end
 end