Handle event for PRs being closed

This didn't exist previously. Will require an updated pipeline stack to
receive event.

Author: ipmb

builder/build/prebuild.go

@@ -29,6 +29,13 @@ var buildkitdConfig = map[string]map[string]map[string][]string{
 	},
 }
 
+const (
+	ClosedPRStatus  = "closed"
+	MergedPRStatus  = "merged"
+	OpenPRStatus    = "open"
+	CreatedPRStatus = "created"
+)
+
 // define a struct named Build
 type Build struct {
 	Appname                string
@@ -255,18 +262,21 @@ func (b *Build) ImageName() (string, error) {
 
 func (b *Build) NewPRStatus() string {
 	if b.CreateReviewApp {
-		return "created"
+		return CreatedPRStatus
 	}
 	if b.CodebuildWebhookEvent == "PULL_REQUEST_CREATED" || b.CodebuildWebhookEvent == "PULL_REQUEST_REOPENED" {
-		return "open"
+		return OpenPRStatus
 	}
 	if b.CodebuildWebhookEvent == "PULL_REQUEST_MERGED" {
-		return "merged"
+		return MergedPRStatus
+	}
+	if b.CodebuildWebhookEvent == "PULL_REQUEST_CLOSED" {
+		return ClosedPRStatus
 	}
 	_, err := b.GetPRStatus()
 	if err != nil {
 		b.Log().Debug().Err(err).Msg("failed to get PR status")
-		return "open"
+		return OpenPRStatus
 	}
 	return ""
 }
@@ -280,7 +290,7 @@ func (b *Build) HandlePR() (bool, error) {
 	}
 	newStatus := b.NewPRStatus()
 	b.Log().Debug().Str("status", newStatus).Msg("PR status")
-	if newStatus == "merged" {
+	if newStatus == MergedPRStatus || newStatus == ClosedPRStatus {
 		hasReviewApp, err := b.ReviewAppStackExists()
 		// TODO err is ignored because it usually means the stack doesn't exist
 		if err != nil {
@@ -310,7 +320,7 @@ func (b *Build) HandlePR() (bool, error) {
 			return false, err
 		}
 	}
-	if status.Status != "created" {
+	if status.Status != CreatedPRStatus {
 		err = b.SkipBuild()
 		return true, err
 	}

builder/build/prebuild_test.go

@@ -527,6 +527,40 @@ func TestHandlePRMergedAndDestroy(t *testing.T) {
 	mockedState.AssertExpectations(t)
 }
 
+func TestHandlePRClosedAndDestroy(t *testing.T) {
+	pr := "pr/123"
+	appName := "test-app"
+	mockedAWS := new(MockAWS)
+	mockedAWS.On(
+		"DescribeStack",
+		fmt.Sprintf("apppack-reviewapp-%s%s", appName, strings.Split(pr, "/")[1]),
+	).Return(&types.Stack{}, nil)
+	mockedAWS.On(
+		"DestroyStack",
+		fmt.Sprintf("apppack-reviewapp-%s%s", appName, strings.Split(pr, "/")[1]),
+	).Return(nil)
+	mockedState := emptyState()
+	b := Build{
+		Appname:                appName,
+		Pipeline:               true,
+		CodebuildSourceVersion: pr,
+		CodebuildWebhookEvent:  "PULL_REQUEST_CLOSED",
+		CodebuildBuildId:       CodebuildBuildId,
+		aws:                    mockedAWS,
+		state:                  mockedState,
+		Ctx:                    testContext,
+	}
+	skip, err := b.HandlePR()
+	if err != nil {
+		t.Error("HandlePR should return nil")
+	}
+	if !skip {
+		t.Error("HandlePR should skip the build when the PR is closed")
+	}
+	mockedAWS.AssertExpectations(t)
+	mockedState.AssertExpectations(t)
+}
+
 func TestRemoveDuplicateStr(t *testing.T) {
 	slice := []string{"a", "b", "c", "a", "b"}
 	expected := []string{"a", "b", "c"}