fix: handle case where deploying app image does not exist

This happens if ps:scale is called before a deploy.

Also refactor GetDeployingAppImageName() to return an error as the second return parameter.

docs/appendices/0.22.0-migration-guide.md

@@ -5,6 +5,7 @@
 - Underscores are no longer valid characters in app names. Please rename applications before upgrading.
 - Process type names specified in Procfile may no longer use characters not valid in DNS Label Names ([RFC 1123](https://tools.ietf.org/html/rfc1123)).
 - The minimum Docker version is now 17.05.0.
+- The `common.GetDeployingAppImageName()` function now returns an `error` as the second return argument instead of calling `common.LogFail()` internally.
 
 ## Removals
 

plugins/app-json/appjson.go

@@ -138,7 +138,10 @@ func getDokkuAppShell(appName string) string {
 }
 
 func executeScript(appName string, imageTag string, phase string) error {
-	image := common.GetDeployingAppImageName(appName, imageTag, "")
+	image, err := common.GetDeployingAppImageName(appName, imageTag, "")
+	if err != nil {
+		common.LogFail(err.Error())
+	}
 	command := ""
 	phaseSource := ""
 	if phase == "release" {

plugins/common/common.go

@@ -89,26 +89,26 @@ func GetGlobalScheduler() string {
 }
 
 // GetDeployingAppImageName returns deploying image identifier for a given app, tag tuple. validate if tag is presented
-func GetDeployingAppImageName(appName, imageTag, imageRepo string) (imageName string) {
+func GetDeployingAppImageName(appName, imageTag, imageRepo string) (string, error) {
 	if appName == "" {
 		LogFail("(GetDeployingAppImageName) APP must not be empty")
 	}
 
 	b, err := PlugnTriggerOutput("deployed-app-repository", []string{appName}...)
 	if err != nil {
-		LogFail(err.Error())
+		return "", err
 	}
 	imageRemoteRepository := string(b[:])
 
 	b, err = PlugnTriggerOutput("deployed-app-image-tag", []string{appName}...)
 	if err != nil {
-		LogFail(err.Error())
+		return "", err
 	}
 	newImageTag := string(b[:])
 
 	b, err = PlugnTriggerOutput("deployed-app-image-repo", []string{appName}...)
 	if err != nil {
-		LogFail(err.Error())
+		return "", err
 	}
 	newImageRepo := string(b[:])
 
@@ -125,11 +125,11 @@ func GetDeployingAppImageName(appName, imageTag, imageRepo string) (imageName st
 		imageTag = "latest"
 	}
 
-	imageName = fmt.Sprintf("%s%s:%s", imageRemoteRepository, imageRepo, imageTag)
+	imageName := fmt.Sprintf("%s%s:%s", imageRemoteRepository, imageRepo, imageTag)
 	if !VerifyImage(imageName) {
-		LogFail(fmt.Sprintf("App image (%s) not found", imageName))
+		return "", fmt.Errorf("App image (%s) not found", imageName)
 	}
-	return
+	return imageName, nil
 }
 
 // GetAppImageRepo is the central definition of a dokku image repo pattern

plugins/ps/subcommands.go

@@ -145,7 +145,11 @@ func CommandScale(appName string, skipDeploy bool, processTuples []string) error
 	procfilePath := getProcfilePath(appName)
 	if !common.FileExists(procfilePath) {
 		extract := func() error {
-			image := common.GetDeployingAppImageName(appName, "", "")
+			image, err := common.GetDeployingAppImageName(appName, "", "")
+			if err != nil {
+				return nil
+			}
+
 			return extractProcfile(appName, image)
 		}
 

plugins/ps/triggers.go

@@ -144,7 +144,11 @@ func TriggerPostStop(appName string) error {
 
 // TriggerPreDeploy ensures an app has an up to date scale file
 func TriggerPreDeploy(appName string, imageTag string) error {
-	image := common.GetDeployingAppImageName(appName, imageTag, "")
+	image, err := common.GetDeployingAppImageName(appName, imageTag, "")
+	if err != nil {
+		return err
+	}
+
 	if err := removeProcfile(appName); err != nil {
 		return err
 	}
@@ -183,7 +187,11 @@ func TriggerProcfileGetCommand(appName string, processType string, port int) err
 	procfilePath := getProcfilePath(appName)
 	if !common.FileExists(procfilePath) {
 		extract := func() error {
-			image := common.GetDeployingAppImageName(appName, "", "")
+			image, err := common.GetDeployingAppImageName(appName, "", "")
+			if err != nil {
+				return err
+			}
+
 			return extractProcfile(appName, image)
 		}