return errors instead of logrus.Fatal calls

This commit refactors the code to remove more or less
all occurences of logrus.Fatalf() from the code under
pkg/ except for app.go where all the errors are being
handled currently.

This is being done since random logrus.Fatalf() calls
all around the code was making handling the errors,
unit testing and troubleshooting a bit more painful.

logrus.Fatalf() calls are either replaced by
return errors.New("new error")
or
return errors.Wrap(err, "annonate error")
calls, and the function signatures are accordingly
changed to accomodate the new return values.

The unit tests which previously used to check
if logrus.Fatalf() calls worked fine have also
been fixed to only check for errors now.

Fixes #416

pkg/loader/compose/compose.go

@@ -33,6 +33,7 @@ import (
 	"github.com/docker/libcompose/project"
 	"github.com/fatih/structs"
 	"github.com/kubernetes-incubator/kompose/pkg/kobject"
+	"github.com/pkg/errors"
 )
 
 // Compose is docker compose file loader, implements Loader interface
@@ -275,7 +276,7 @@ func loadPorts(composePorts []string) ([]kobject.Ports, error) {
 }
 
 // LoadFile loads compose file into KomposeObject
-func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
+func (c *Compose) LoadFile(files []string) (kobject.KomposeObject, error) {
 	komposeObject := kobject.KomposeObject{
 		ServiceConfigs: make(map[string]kobject.ServiceConfig),
 		LoadedFrom:     "compose",
@@ -290,7 +291,7 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 	if context.EnvironmentLookup == nil {
 		cwd, err := os.Getwd()
 		if err != nil {
-			return kobject.KomposeObject{}
+			return kobject.KomposeObject{}, nil
 		}
 		context.EnvironmentLookup = &lookup.ComposableEnvLookup{
 			Lookups: []config.EnvironmentLookup{
@@ -306,7 +307,7 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 	composeObject := project.NewProject(context, nil, nil)
 	err := composeObject.Parse()
 	if err != nil {
-		log.Fatalf("Failed to load compose file: %v", err)
+		return kobject.KomposeObject{}, errors.Wrap(err, "composeObject.Parse() failed, Failed to load compose file")
 	}
 
 	noSupKeys := checkUnsupportedKey(composeObject)
@@ -329,7 +330,7 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 		// load ports
 		ports, err := loadPorts(composeServiceConfig.Ports)
 		if err != nil {
-			log.Fatalf("%q failed to load ports from compose file: %v", name, err)
+			return kobject.KomposeObject{}, errors.Wrap(err, "loadPorts failed. "+name+" failed to load ports from compose file")
 		}
 		serviceConfig.Port = ports
 
@@ -347,7 +348,12 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 		for key, value := range composeServiceConfig.Labels {
 			switch key {
 			case "kompose.service.type":
-				serviceConfig.ServiceType = handleServiceType(value)
+				serviceType, err := handleServiceType(value)
+				if err != nil {
+					return kobject.KomposeObject{}, errors.Wrap(err, "handleServiceType failed")
+				}
+
+				serviceConfig.ServiceType = serviceType
 			case "kompose.service.expose":
 				serviceConfig.ExposeService = strings.ToLower(value)
 			}
@@ -373,20 +379,19 @@ func (c *Compose) LoadFile(files []string) kobject.KomposeObject {
 		komposeObject.ServiceConfigs[name] = serviceConfig
 	}
 
-	return komposeObject
+	return komposeObject, nil
 }
 
-func handleServiceType(ServiceType string) string {
+func handleServiceType(ServiceType string) (string, error) {
 	switch strings.ToLower(ServiceType) {
 	case "", "clusterip":
-		return string(api.ServiceTypeClusterIP)
+		return string(api.ServiceTypeClusterIP), nil
 	case "nodeport":
-		return string(api.ServiceTypeNodePort)
+		return string(api.ServiceTypeNodePort), nil
 	case "loadbalancer":
-		return string(api.ServiceTypeLoadBalancer)
+		return string(api.ServiceTypeLoadBalancer), nil
 	default:
-		log.Fatalf("Unknown value '%s', supported values are 'NodePort, ClusterIP or LoadBalancer'", ServiceType)
-		return ""
+		return "", errors.New("Unknown value " + ServiceType + " , supported values are 'NodePort, ClusterIP or LoadBalancer'")
 	}
 }
 

pkg/loader/compose/compose_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/docker/libcompose/config"
 	"github.com/docker/libcompose/project"
 	"github.com/docker/libcompose/yaml"
+	"github.com/pkg/errors"
 )
 
 // Test if service types are parsed properly on user input
@@ -47,7 +48,10 @@ func TestHandleServiceType(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		result := handleServiceType(tt.labelValue)
+		result, err := handleServiceType(tt.labelValue)
+		if err != nil {
+			t.Error(errors.Wrap(err, "handleServiceType failed"))
+		}
 		if result != tt.serviceType {
 			t.Errorf("Expected %q, got %q", tt.serviceType, result)
 		}