Add blob viewer for metrics dashboard yaml files

To enable validation of metrics dashboard definitions in yaml files
we need to enable to display blobs containing that file to be displayed
in auxiliary mode.

app/models/blob.rb

@@ -50,6 +50,7 @@ class Blob < SimpleDelegator
     BlobViewer::License,
     BlobViewer::Contributing,
     BlobViewer::Changelog,
+    BlobViewer::MetricsDashboardYml,
 
     BlobViewer::CargoToml,
     BlobViewer::Cartfile,

app/models/blob_viewer/metrics_dashboard_yml.rb

+# frozen_string_literal: true
+
+module BlobViewer
+  class MetricsDashboardYml < Base
+    include ServerSide
+    include Gitlab::Utils::StrongMemoize
+    include Auxiliary
+
+    self.partial_name = 'metrics_dashboard_yml'
+    self.loading_partial_name = 'metrics_dashboard_yml_loading'
+    self.file_types = %i(metrics_dashboard)
+    self.binary = false
+
+    def valid?
+      errors.blank?
+    end
+
+    def errors
+      strong_memoize(:errors) do
+        prepare!
+        parse_blob_data
+      end
+    end
+
+    private
+
+    def parse_blob_data
+      ::PerformanceMonitoring::PrometheusDashboard.from_json(YAML.safe_load(blob.data))
+      nil
+    rescue Psych::SyntaxError => error
+      wrap_yml_syntax_error(error)
+    rescue ActiveModel::ValidationError => invalid
+      invalid.model.errors
+    end
+
+    def wrap_yml_syntax_error(error)
+      ::PerformanceMonitoring::PrometheusDashboard.new.errors.tap do |errors|
+        errors.add(:'YAML syntax', error.message)
+      end
+    end
+  end
+end

app/models/performance_monitoring/prometheus_dashboard.rb

@@ -13,7 +13,7 @@ module PerformanceMonitoring
       def from_json(json_content)
         dashboard = new(
           dashboard: json_content['dashboard'],
-          panel_groups: json_content['panel_groups'].map { |group| PrometheusPanelGroup.from_json(group) }
+          panel_groups: json_content['panel_groups']&.map { |group| PrometheusPanelGroup.from_json(group) }
         )
 
         dashboard.tap(&:validate!)

app/models/performance_monitoring/prometheus_panel.rb

@@ -15,7 +15,7 @@ module PerformanceMonitoring
         title: json_content['title'],
         y_label: json_content['y_label'],
         weight: json_content['weight'],
-        metrics: json_content['metrics'].map { |metric| PrometheusMetric.from_json(metric) }
+        metrics: json_content['metrics']&.map { |metric| PrometheusMetric.from_json(metric) }
       )
 
       panel.tap(&:validate!)

app/models/performance_monitoring/prometheus_panel_group.rb

@@ -13,7 +13,7 @@ module PerformanceMonitoring
       panel_group = new(
         group: json_content['group'],
         priority: json_content['priority'],
-        panels: json_content['panels'].map { |panel| PrometheusPanel.from_json(panel) }
+        panels: json_content['panels']&.map { |panel| PrometheusPanel.from_json(panel) }
       )
 
       panel_group.tap(&:validate!)

app/views/projects/blob/viewers/_metrics_dashboard_yml.html.haml

+- if viewer.valid?
+  = icon('check fw')
+  = _('Metrics Dashboard YAML definition is valid.')
+- else
+  = icon('warning fw')
+  = _('Metrics Dashboard YAML definition is invalid:')
+  %ul
+    - viewer.errors.messages.each do |error|
+      %li= error.join(': ')
+
+= link_to _('Learn more'), help_page_path('user/project/integrations/prometheus.md', anchor: 'defining-custom-dashboards-per-project')

app/views/projects/blob/viewers/_metrics_dashboard_yml_loading.html.haml

+= icon('spinner spin fw')
+= _('Metrics Dashboard YAML definition') + '…'
+
+= link_to _('Learn more'), help_page_path('user/project/integrations/prometheus.md')

changelogs/unreleased/mwaw-210289-metrics-dashboard-file-validation-mvc-1.yml

+---
+title: Added validation for YAML files with metrics dashboard definitions.
+merge_request: 33202
+author:
+type: added

doc/user/project/integrations/prometheus.md

@@ -326,6 +326,33 @@ new branch.
 If you select your **default** branch, the new dashboard becomes immediately available.
 If you select another branch, this branch should be merged to your **default** branch first.
 
+#### Dashboard YAML syntax validation
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/33202) in GitLab 13.1.
+
+To confirm your dashboard definition contains valid YAML syntax:
+
+1. Navigate to **{doc-text}** **Repository > Files**.
+1. Navigate to your dashboard file in your repository.
+1. Review the information pane about the file, displayed above the file contents.
+
+Files with valid syntax display **Metrics Dashboard YAML definition is valid**,
+and files with invalid syntax display **Metrics Dashboard YAML definition is invalid**.
+
+![Metrics Dashboard_YAML_syntax_validation](img/prometheus_dashboard_yaml_validation_v13_1.png)
+
+When **Metrics Dashboard YAML definition is invalid** at least one of the following messages is displayed:
+
+1. `dashboard: can't be blank` [learn more](#dashboard-top-level-properties)
+1. `panel_groups: can't be blank` [learn more](#dashboard-top-level-properties)
+1. `group: can't be blank` [learn more](#panel-group-panel_groups-properties)
+1. `panels: can't be blank` [learn more](#panel-group-panel_groups-properties)
+1. `metrics: can't be blank` [learn more](#panel-panels-properties)
+1. `title: can't be blank` [learn more](#panel-panels-properties)
+1. `query: can't be blank` [learn more](#metrics-metrics-properties)
+1. `query_range: can't be blank` [learn more](#metrics-metrics-properties)
+1. `unit: can't be blank` [learn more](#metrics-metrics-properties)
+
 #### Dashboard YAML properties
 
 Dashboards have several components:

locale/gitlab.pot

@@ -13753,6 +13753,15 @@ msgstr ""
 msgid "Metrics Dashboard"
 msgstr ""
 
+msgid "Metrics Dashboard YAML definition"
+msgstr ""
+
+msgid "Metrics Dashboard YAML definition is invalid:"
+msgstr ""
+
+msgid "Metrics Dashboard YAML definition is valid."
+msgstr ""
+
 msgid "Metrics and profiling"
 msgstr ""
 

spec/features/projects/blobs/blob_show_spec.rb

@@ -555,6 +555,53 @@ describe 'File blob', :js do
     end
   end
 
+  describe '.gitlab/dashboards/custom-dashboard.yml' do
+    before do
+      project.add_maintainer(project.creator)
+
+      Files::CreateService.new(
+        project,
+        project.creator,
+        start_branch: 'master',
+        branch_name: 'master',
+        commit_message: "Add .gitlab/dashboards/custom-dashboard.yml",
+        file_path: '.gitlab/dashboards/custom-dashboard.yml',
+        file_content: file_content
+      ).execute
+
+      visit_blob('.gitlab/dashboards/custom-dashboard.yml')
+    end
+
+    context 'valid dashboard file' do
+      let(:file_content) { File.read(Rails.root.join('config/prometheus/common_metrics.yml')) }
+
+      it 'displays an auxiliary viewer' do
+        aggregate_failures do
+          # shows that dashboard yaml is valid
+          expect(page).to have_content('Metrics Dashboard YAML definition is valid.')
+
+          # shows a learn more link
+          expect(page).to have_link('Learn more')
+        end
+      end
+    end
+
+    context 'invalid dashboard file' do
+      let(:file_content) { "dashboard: 'invalid'" }
+
+      it 'displays an auxiliary viewer' do
+        aggregate_failures do
+          # shows that dashboard yaml is invalid
+          expect(page).to have_content('Metrics Dashboard YAML definition is invalid:')
+          expect(page).to have_content("panel_groups: can't be blank")
+
+          # shows a learn more link
+          expect(page).to have_link('Learn more')
+        end
+      end
+    end
+  end
+
   context 'LICENSE' do
     before do
       visit_blob('LICENSE')

spec/models/blob_viewer/metrics_dashboard_yml_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe BlobViewer::MetricsDashboardYml do
+  include FakeBlobHelpers
+  include RepoHelpers
+
+  let_it_be(:project) { create(:project, :repository) }
+  let(:blob) { fake_blob(path: '.gitlab/dashboards/custom-dashboard.yml', data: data) }
+  let(:sha) { sample_commit.id }
+
+  subject(:viewer) { described_class.new(blob) }
+
+  context 'when the definition is valid' do
+    let(:data) { File.read(Rails.root.join('config/prometheus/common_metrics.yml')) }
+
+    describe '#valid?' do
+      it 'calls prepare! on the viewer' do
+        allow(PerformanceMonitoring::PrometheusDashboard).to receive(:from_json)
+
+        expect(viewer).to receive(:prepare!)
+
+        viewer.valid?
+      end
+
+      it 'returns true' do
+        expect(PerformanceMonitoring::PrometheusDashboard)
+          .to receive(:from_json).with(YAML.safe_load(data))
+        expect(viewer.valid?).to be_truthy
+      end
+    end
+
+    describe '#errors' do
+      it 'returns nil' do
+        allow(PerformanceMonitoring::PrometheusDashboard).to receive(:from_json)
+
+        expect(viewer.errors).to be nil
+      end
+    end
+  end
+
+  context 'when definition is invalid' do
+    let(:error) { ActiveModel::ValidationError.new(PerformanceMonitoring::PrometheusDashboard.new.tap(&:validate)) }
+    let(:data) do
+      <<~YAML
+        dashboard:
+      YAML
+    end
+
+    describe '#valid?' do
+      it 'returns false' do
+        expect(PerformanceMonitoring::PrometheusDashboard)
+          .to receive(:from_json).and_raise(error)
+
+        expect(viewer.valid?).to be_falsey
+      end
+    end
+
+    describe '#errors' do
+      it 'returns validation errors' do
+        allow(PerformanceMonitoring::PrometheusDashboard)
+          .to receive(:from_json).and_raise(error)
+
+        expect(viewer.errors).to be error.model.errors
+      end
+    end
+  end
+
+  context 'when YAML syntax is invalid' do
+    let(:data) do
+      <<~YAML
+        dashboard: 'empty metrics'
+         panel_groups:
+        - group: 'Group Title'
+      YAML
+    end
+
+    describe '#valid?' do
+      it 'returns false' do
+        expect(PerformanceMonitoring::PrometheusDashboard).not_to receive(:from_json)
+        expect(viewer.valid?).to be_falsey
+      end
+    end
+
+    describe '#errors' do
+      it 'returns validation errors' do
+        yaml_wrapped_errors = { 'YAML syntax': ["(<unknown>): did not find expected key while parsing a block mapping at line 1 column 1"] }
+
+        expect(viewer.errors).to be_kind_of ActiveModel::Errors
+        expect(viewer.errors.messages).to eql(yaml_wrapped_errors)
+      end
+    end
+  end
+end

spec/models/performance_monitoring/prometheus_dashboard_spec.rb

@@ -38,24 +38,123 @@ describe PerformanceMonitoring::PrometheusDashboard do
     end
 
     describe 'validations' do
-      context 'when dashboard is missing' do
-        before do
-          json_content['dashboard'] = nil
+      shared_examples 'validation failed' do |errors_messages|
+        it 'raises error with corresponding messages', :aggregate_failures do
+          expect { subject }.to raise_error do |error|
+            expect(error).to be_kind_of(ActiveModel::ValidationError)
+            expect(error.model.errors.messages).to eql(errors_messages)
+          end
+        end
       end
 
-        subject { described_class.from_json(json_content) }
+      context 'dashboard definition is missing panels_groups and dashboard keys' do
+        let(:json_content) do
+          {
+            "dashboard" => nil
+          }
+        end
 
-        it { expect { subject }.to raise_error(ActiveModel::ValidationError) }
+        it_behaves_like 'validation failed', panel_groups: ["can't be blank"], dashboard: ["can't be blank"]
+      end
+
+      context 'group definition is missing panels and group keys' do
+        let(:json_content) do
+          {
+            "dashboard" => "Dashboard Title",
+            "templating" => {
+              "variables" => {
+                "variable1" => %w(value1 value2 value3)
+              }
+            },
+            "panel_groups" => [{ "group" => nil }]
+          }
         end
 
-      context 'when panel groups are missing' do
-        before do
-          json_content['panel_groups'] = []
+        it_behaves_like 'validation failed', panels: ["can't be blank"], group: ["can't be blank"]
       end
 
-        subject { described_class.from_json(json_content) }
+      context 'panel definition is missing metrics and title keys' do
+        let(:json_content) do
+          {
+            "dashboard" => "Dashboard Title",
+            "templating" => {
+              "variables" => {
+                "variable1" => %w(value1 value2 value3)
+              }
+            },
+            "panel_groups" => [{
+              "group" => "Group Title",
+              "panels" => [{
+                "type" => "area-chart",
+                "y_label" => "Y-Axis"
+              }]
+            }]
+          }
+        end
+
+        it_behaves_like 'validation failed', metrics: ["can't be blank"], title: ["can't be blank"]
+      end
+
+      context 'metrics definition is missing unit, query and query_range keys' do
+        let(:json_content) do
+          {
+            "dashboard" => "Dashboard Title",
+            "templating" => {
+              "variables" => {
+                "variable1" => %w(value1 value2 value3)
+              }
+            },
+            "panel_groups" => [{
+              "group" => "Group Title",
+              "panels" => [{
+                "type" => "area-chart",
+                "title" => "Chart Title",
+                "y_label" => "Y-Axis",
+                "metrics" => [{
+                  "id" => "metric_of_ages",
+                  "label" => "Metric of Ages",
+                  "query_range" => nil
+                }]
+              }]
+            }]
+          }
+        end
+
+        it_behaves_like 'validation failed', unit: ["can't be blank"], query_range: ["can't be blank"], query: ["can't be blank"]
+      end
+
+      # for each parent entry validation first is done to its children,
+      # whole execution is stopped on first encountered error
+      # which is the one that is reported
+      context 'multiple offences on different levels' do
+        let(:json_content) do
+          {
+            "dashboard" => nil,
+            "panel_groups" => [{
+              "group" => nil,
+              "panels" => [{
+                "type" => "area-chart",
+                "title" => nil,
+                "y_label" => "Y-Axis",
+                "metrics" => [{
+                  "id" => "metric_of_ages",
+                  "label" => "Metric of Ages",
+                  "query_range" => 'query'
+                }, {
+                  "id" => "metric_of_ages",
+                  "unit" => "count",
+                  "label" => "Metric of Ages",
+                  "query_range" => nil
+                }]
+              }]
+            }, {
+              "group" => 'group',
+              "panels" => nil
+            }]
+          }
+        end
 
-        it { expect { subject }.to raise_error(ActiveModel::ValidationError) }
+        it_behaves_like 'validation failed', unit: ["can't be blank"]
       end
     end
   end

spec/models/performance_monitoring/prometheus_panel_group_spec.rb

@@ -32,7 +32,7 @@ describe PerformanceMonitoring::PrometheusPanelGroup do
     describe 'validations' do
       context 'when group is missing' do
         before do
-          json_content['group'] = nil
+          json_content.delete('group')
         end
 
         subject { described_class.from_json(json_content) }

spec/models/performance_monitoring/prometheus_panel_spec.rb

@@ -54,7 +54,7 @@ describe PerformanceMonitoring::PrometheusPanel do
 
       context 'when metrics are missing' do
         before do
-          json_content['metrics'] = []
+          json_content.delete('metrics')
         end
 
         subject { described_class.from_json(json_content) }