Only run xpack siem cypress in PRs when there are siem changes

Jenkinsfile

@@ -6,6 +6,10 @@ kibanaLibrary.load()
 kibanaPipeline(timeoutMinutes: 135, checkPrChanges: true) {
   githubPr.withDefaultPrComments {
     catchError {
+      whenChanged(/^vars\//) {
+        print "Testing"
+      }
+
       retryable.enable()
       parallel([
         'kibana-intake-agent': workers.intake('kibana-intake', './test/scripts/jenkins_unit.sh'),
@@ -40,7 +44,10 @@ kibanaPipeline(timeoutMinutes: 135, checkPrChanges: true) {
           'xpack-ciGroup9': kibanaPipeline.xpackCiGroupProcess(9),
           'xpack-ciGroup10': kibanaPipeline.xpackCiGroupProcess(10),
           'xpack-accessibility': kibanaPipeline.functionalTestProcess('xpack-accessibility', './test/scripts/jenkins_xpack_accessibility.sh'),
-          'xpack-siemCypress': kibanaPipeline.functionalTestProcess('xpack-siemCypress', './test/scripts/jenkins_siem_cypress.sh'),
+          'xpack-siemCypress': {
+            whenChanged(/^x-pack\/legacy\/plugins\/siem\//, kibanaPipeline.functionalTestProcess('xpack-siemCypress', './test/scripts/jenkins_siem_cypress.sh'))
+          },
+
           // 'xpack-visualRegression': kibanaPipeline.functionalTestProcess('xpack-visualRegression', './test/scripts/jenkins_xpack_visual_regression.sh'),
         ]),
       ])

vars/prChanges.groovy

@@ -1,3 +1,4 @@
+public static @Field PR_CHANGES_CACHE = null
 
 def getSkippablePaths() {
   return [
@@ -36,9 +37,13 @@ def areChangesSkippable() {
 }
 
 def getChanges() {
-  withGithubCredentials {
-    return githubPrs.getChanges(env.ghprbPullId)
+  if (!PR_CHANGES_CACHE && env.ghprbPullId) {
+    withGithubCredentials {
+      PR_CHANGES_CACHE = githubPrs.getChanges(env.ghprbPullId)
+    }
   }
+
+  return PR_CHANGES_CACHE
 }
 
 def getChangedFiles() {

vars/whenChanged.groovy

@@ -0,0 +1,19 @@
+def call(String regex, Closure closure) {
+  if (!githubPr.isPr()) {
+    return closure()
+  }
+
+  print "Checking PR for changes that match: ${regex}"
+
+  def files = prChanges.getChangedFiles()
+  def hasMatch = !!files.find { file -> file =~ regex }
+
+  if (hasMatch) {
+    print "Changes found, executing pipeline."
+    closure()
+  } else {
+    print "No changes found, skipping."
+  }
+}
+
+return this

x-pack/legacy/plugins/siem/index.ts

@@ -4,6 +4,7 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
+// TODO remove me
 import { i18n } from '@kbn/i18n';
 import { resolve } from 'path';
 import { Server } from 'hapi';