Populate CI_MERGE_REQUEST_CHANGED_PAGE_* variables

- Added CI_MERGE_REQUEST_CHANGED_PAGE_PATHS
- Added CI_MERGE_REQUEST_CHANGED_PAGE_URLS

app/models/ci/build.rb

@@ -531,6 +531,7 @@ module Ci
           .concat(persisted_variables)
           .concat(scoped_variables)
           .concat(job_variables)
+          .concat(environment_changed_page_variables)
           .concat(persisted_environment_variables)
           .to_runner_variables
       end
@@ -569,6 +570,15 @@ module Ci
       end
     end
 
+    def environment_changed_page_variables
+      Gitlab::Ci::Variables::Collection.new.tap do |variables|
+        break variables unless environment_status
+
+        variables.append(key: 'CI_MERGE_REQUEST_CHANGED_PAGE_PATHS', value: environment_status.changed_paths.join(','))
+        variables.append(key: 'CI_MERGE_REQUEST_CHANGED_PAGE_URLS', value: environment_status.changed_urls.join(','))
+      end
+    end
+
     def deploy_token_variables
       Gitlab::Ci::Variables::Collection.new.tap do |variables|
         break variables unless gitlab_deploy_token
@@ -970,6 +980,14 @@ module Ci
       options&.dig(:environment, :url) || persisted_environment&.external_url
     end
 
+    def environment_status
+      strong_memoize(:environment_status) do
+        if has_environment? && merge_request
+          EnvironmentStatus.new(project, persisted_environment, merge_request, pipeline.sha)
+        end
+      end
+    end
+
     # The format of the retry option changed in GitLab 11.5: Before it was
     # integer only, after it is a hash. New builds are created with the new
     # format, but builds created before GitLab 11.5 and saved in database still

app/models/environment_status.rb

@@ -62,9 +62,9 @@ class EnvironmentStatus
   end
 
   def changes
-    return [] unless has_route_map?
-
-    changed_files.map { |file| build_change(file) }.compact
+    strong_memoize(:changes) do
+      has_route_map? ? changed_files.map { |file| build_change(file) }.compact : []
+    end
   end
 
   def changed_files
@@ -72,6 +72,14 @@ class EnvironmentStatus
       .merge_request_diff_files.where(deleted_file: false)
   end
 
+  def changed_paths
+    changes.map { |change| change[:path] }
+  end
+
+  def changed_urls
+    changes.map { |change| change[:external_url] }
+  end
+
   def has_route_map?
     project.route_map_for(sha).present?
   end

changelogs/unreleased/changed-pages-ci-var.yml

+---
+title: Added CI_MERGE_REQUEST_CHANGED_PAGE_* to Predefined Variables reference
+merge_request: 25256
+author:
+type: added

doc/ci/variables/predefined_variables.md

@@ -64,6 +64,8 @@ future GitLab releases.**
 | `CI_JOB_TOKEN`                                | 9.0    | 1.2    | Token used for authenticating with the [GitLab Container Registry][registry] and downloading [dependent repositories][dependent-repositories]                                                                                                                                                                                                              |
 | `CI_JOB_URL`                                  | 11.1   | 0.5    | Job details URL                                                                                                                                                                                                                                                                                                                                            |
 | `CI_MERGE_REQUEST_ASSIGNEES`                  | 11.9   | all    | Comma-separated list of username(s) of assignee(s) for the merge request if [the pipelines are for merge requests](../merge_request_pipelines/index.md). Available only if `only: [merge_requests]` is used and the merge request is created.                                                                                                              |
+| `CI_MERGE_REQUEST_CHANGED_PAGE_PATHS`         | 12.9   | all    | Comma-separated list of paths of changed pages in a deployed [Review App](../review_apps/index.md) for a [Merge Request](../merge_request_pipelines/index.md). A [Route Map](../review_apps/index.md#route-maps) must be configured.                                                                                 |
+| `CI_MERGE_REQUEST_CHANGED_PAGE_URLS`          | 12.9   | all    | Comma-separated list of URLs of changed pages in a deployed [Review App](../review_apps/index.md) for a [Merge Request](../merge_request_pipelines/index.md). A [Route Map](../review_apps/index.md#route-maps) must be configured.                                                                                  |
 | `CI_MERGE_REQUEST_ID`                         | 11.6   | all    | The ID of the merge request if [the pipelines are for merge requests](../merge_request_pipelines/index.md). Available only if `only: [merge_requests]` is used and the merge request is created.                                                                                                                                                           |
 | `CI_MERGE_REQUEST_IID`                        | 11.6   | all    | The IID of the merge request if [the pipelines are for merge requests](../merge_request_pipelines/index.md). Available only if `only: [merge_requests]` is used and the merge request is created.                                                                                                                                                          |
 | `CI_MERGE_REQUEST_LABELS`                     | 11.9   | all    | Comma-separated label names of the merge request if [the pipelines are for merge requests](../merge_request_pipelines/index.md). Available only if `only: [merge_requests]` is used and the merge request is created.                                                                                                                                      |

spec/models/ci/build_spec.rb

@@ -2509,6 +2509,64 @@ describe Ci::Build do
       end
     end
 
+    describe 'CHANGED_PAGES variables' do
+      let(:route_map_yaml) do
+        <<~ROUTEMAP
+        - source: 'bar/branch-test.txt'
+          public: '/bar/branches'
+        ROUTEMAP
+      end
+
+      before do
+        allow_any_instance_of(Project)
+          .to receive(:route_map_for).with(/.+/)
+          .and_return(Gitlab::RouteMap.new(route_map_yaml))
+      end
+
+      context 'with a deployment environment and a merge request' do
+        let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
+        let(:environment)   { create(:environment, project: merge_request.project, name: "foo-#{project.default_branch}") }
+        let(:build)         { create(:ci_build, pipeline: pipeline, environment: environment.name) }
+
+        it 'populates CI_MERGE_REQUEST_CHANGED_PAGES_* variables' do
+          expect(subject).to include(
+            { key: 'CI_MERGE_REQUEST_CHANGED_PAGE_PATHS', value: '/bar/branches', public: true, masked: false },
+            { key: 'CI_MERGE_REQUEST_CHANGED_PAGE_URLS', value: File.join(environment.external_url, '/bar/branches'), public: true, masked: false }
+          )
+        end
+
+        context 'with a deployment environment and no merge request' do
+          let(:environment)   { create(:environment, project: project, name: "foo-#{project.default_branch}") }
+          let(:build)         { create(:ci_build, pipeline: pipeline, environment: environment.name) }
+
+          it 'does not append CHANGED_PAGES variables' do
+            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
+
+            expect(ci_variables).to be_empty
+          end
+        end
+
+        context 'with no deployment environment and a present merge request' do
+          let(:merge_request) { create(:merge_request, :with_detached_merge_request_pipeline, source_project: project, target_project: project) }
+          let(:build)         { create(:ci_build, pipeline: merge_request.all_pipelines.take) }
+
+          it 'does not append CHANGED_PAGES variables' do
+            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
+
+            expect(ci_variables).to be_empty
+          end
+        end
+
+        context 'with no deployment environment and no merge request' do
+          it 'does not append CHANGED_PAGES variables' do
+            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
+
+            expect(ci_variables).to be_empty
+          end
+        end
+      end
+    end
+
     context 'when build has user' do
       let(:user_variables) do
         [

spec/models/environment_status_spec.rb

@@ -51,8 +51,10 @@ describe EnvironmentStatus do
   # - source: /files\/(.+)/
   #   public: '\1'
   describe '#changes' do
+    subject { environment_status.changes }
+
     it 'contains only added and modified public pages' do
-      expect(environment_status.changes).to contain_exactly(
+      expect(subject).to contain_exactly(
         {
           path: 'ruby-style-guide.html',
           external_url: "#{environment.external_url}/ruby-style-guide.html"
@@ -64,6 +66,18 @@ describe EnvironmentStatus do
     end
   end
 
+  describe '#changed_paths' do
+    subject { environment_status.changed_urls }
+
+    it { is_expected.to contain_exactly("#{environment.external_url}/ruby-style-guide.html", "#{environment.external_url}/html/page.html") }
+  end
+
+  describe '#changed_urls' do
+    subject { environment_status.changed_paths }
+
+    it { is_expected.to contain_exactly('ruby-style-guide.html', 'html/page.html') }
+  end
+
   describe '.for_merge_request' do
     let(:admin) { create(:admin) }
     let!(:pipeline) { create(:ci_pipeline, sha: sha, merge_requests_as_head_pipeline: [merge_request]) }