Skip CI based on changes in PR (elastic#59939)

Jenkinsfile

@@ -3,7 +3,7 @@
 library 'kibana-pipeline-library'
 kibanaLibrary.load()
 
-kibanaPipeline(timeoutMinutes: 135) {
+kibanaPipeline(timeoutMinutes: 135, checkPrChanges: true) {
   githubPr.withDefaultPrComments {
     catchError {
       retryable.enable()

vars/githubPr.groovy

@@ -194,14 +194,6 @@ def getNextCommentMessage(previousCommentInfo = [:]) {
     .join("\n\n")
 }
 
-def withGithubCredentials(closure) {
-  withCredentials([
-    string(credentialsId: '2a9602aa-ab9f-4e52-baf3-b71ca88469c7', variable: 'GITHUB_TOKEN'),
-  ]) {
-    closure()
-  }
-}
-
 def postComment(message) {
   if (!isPr()) {
     error "Trying to post a GitHub PR comment on a non-PR or non-elastic PR build"

vars/kibanaPipeline.groovy

@@ -185,17 +185,26 @@ def runErrorReporter() {
 }
 
 def call(Map params = [:], Closure closure) {
-  def config = [timeoutMinutes: 135] + params
+  def config = [timeoutMinutes: 135, checkPrChanges: false] + params
 
   stage("Kibana Pipeline") {
     timeout(time: config.timeoutMinutes, unit: 'MINUTES') {
       timestamps {
         ansiColor('xterm') {
+          if (config.checkPrChanges && githubPr.isPr()) {
+            print "Checking PR for changes to determine if CI needs to be run..."
+
+            if (prChanges.areChangesSkippable()) {
+              print "No changes requiring CI found in PR, skipping."
+              return
+            }
+          }
           closure()
         }
       }
     }
   }
 }
 
+
 return this

vars/prChanges.groovy

@@ -0,0 +1,52 @@
+
+def getSkippablePaths() {
+  return [
+    /^docs\//,
+    /^rfcs\//,
+    /^.ci\/.+\.yml$/,
+    /^\.github\//,
+    /\.md$/,
+  ]
+}
+
+def areChangesSkippable() {
+  if (!githubPr.isPr()) {
+    return false
+  }
+
+  try {
+    def skippablePaths = getSkippablePaths()
+    def files = getChangedFiles()
+
+    // 3000 is the max files GH API will return
+    if (files.size() >= 3000) {
+      return false
+    }
+
+    files = files.findAll { file ->
+      return !skippablePaths.find { regex -> file =~ regex}
+    }
+
+    return files.size() < 1
+  } catch (ex) {
+    buildUtils.printStacktrace(ex)
+    print "Error while checking to see if CI is skippable based on changes. Will run CI."
+    return false
+  }
+}
+
+def getChanges() {
+  withGithubCredentials {
+    return githubPrs.getChanges(env.ghprbPullId)
+  }
+}
+
+def getChangedFiles() {
+  def changes = getChanges()
+  def changedFiles = changes.collect { it.filename }
+  def renamedFiles = changes.collect { it.previousFilename }.findAll { it }
+
+  return changedFiles + renamedFiles
+}
+
+return this

vars/withGithubCredentials.groovy

@@ -0,0 +1,9 @@
+def call(closure) {
+  withCredentials([
+    string(credentialsId: '2a9602aa-ab9f-4e52-baf3-b71ca88469c7', variable: 'GITHUB_TOKEN'),
+  ]) {
+    closure()
+  }
+}
+
+return this