report feature flag changes for approval

refs DE-777

Change-Id: I4bfa74ec75894eb93660e2e8ef0e1d75ec51d927
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/269865
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Andrea Cirulli <andrea.cirulli@instructure.com>
Reviewed-by: Ryan Norton <rnorton@instructure.com>
Product-Review: Ryan Norton <rnorton@instructure.com>
QA-Review: Aaron Ogata <aogata@instructure.com>

Jenkinsfile

@@ -440,6 +440,7 @@ pipeline {
                   def nestedStages = [:]
 
                   callableWithDelegate(lintersStage.codeStage(nestedStages))()
+                  callableWithDelegate(lintersStage.featureFlagStage(nestedStages, buildConfig))()
                   callableWithDelegate(lintersStage.groovyStage(nestedStages, buildConfig))()
                   callableWithDelegate(lintersStage.masterBouncerStage(nestedStages))()
                   callableWithDelegate(lintersStage.webpackStage(nestedStages))()

build/new-jenkins/library/vars/filesChangedStage.groovy

@@ -24,6 +24,10 @@ def hasDockerDevFiles(buildConfig) {
   return buildConfig[STAGE_NAME].value('dockerDevFiles')
 }
 
+def hasFeatureFlagFiles(buildConfig) {
+  return buildConfig[STAGE_NAME].value('featureFlagFiles')
+}
+
 def hasGroovyFiles(buildConfig) {
   return buildConfig[STAGE_NAME].value('groovyFiles')
 }
@@ -52,6 +56,7 @@ def call(stageConfig) {
   ]
 
   stageConfig.value('dockerDevFiles', git.changedFiles(dockerDevFiles, 'HEAD^'))
+  stageConfig.value('featureFlagFiles', git.changedFiles(['config/feature_flags'], 'HEAD^'))
   stageConfig.value('groovyFiles', git.changedFiles(['.*.groovy', 'Jenkinsfile.*'], 'HEAD^'))
   stageConfig.value('yarnFiles', git.changedFiles(['package.json', 'yarn.lock'], 'HEAD^'))
   stageConfig.value('migrationFiles', sh(script: 'build/new-jenkins/check-for-migrations.sh', returnStatus: true) == 0)

build/new-jenkins/library/vars/lintersStage.groovy

@@ -26,7 +26,7 @@ def nodeRequirementsTemplate() {
     ]
   ]
 
-  def containers = ['code', 'groovy', 'master-bouncer', 'webpack', 'yarn'].collect { containerName ->
+  def containers = ['code', 'feature-flag', 'groovy', 'master-bouncer', 'webpack', 'yarn'].collect { containerName ->
     baseTestContainer + [name: containerName]
   }
 
@@ -87,6 +87,26 @@ def webpackStage(stages) {
   }
 }
 
+def featureFlagStage(stages, buildConfig) {
+  { ->
+    extendedStage('Linters - feature-flag')
+      .nodeRequirements(container: 'feature-flag')
+      .obeysAllowStages(false)
+      .required(filesChangedStage.hasFeatureFlagFiles(buildConfig))
+      .queue(stages) {
+        slackSend(
+          channel: configuration.getString('feature-flag-report-channel'),
+          color: 'warning',
+          message: "${env.GERRIT_CHANGE_URL} is changing a feature flag."
+        )
+
+        node('master') {
+          gerrit.addReviewers(Arrays.asList(configuration.getString('feature-flag-report-emails').split(',')))
+        }
+      }
+  }
+}
+
 def yarnStage(stages, buildConfig) {
   { ->
     def yarnEnvVars = [