Enhance error handling

cmd/stackDeploy.go

@@ -48,12 +48,11 @@ var stackDeployCmd = &cobra.Command{
 		}
 
 		endpointSwarmClusterId, selectionErr := common.GetEndpointSwarmClusterId(endpointId)
-		switch selectionErr.(type) {
+		if selectionErr == nil {
-		case nil:
 			// It's a swarm cluster
-		case *common.StackClusterNotFoundError:
+		} else if selectionErr == common.ErrStackClusterNotFound {
 			// It's not a swarm cluster
-		default:
+		} else {
 			// Something else happened
 			common.CheckError(selectionErr)
 		}
@@ -63,8 +62,7 @@ var stackDeployCmd = &cobra.Command{
 			"endpoint": endpointId,
 		}).Debug("Getting stack")
 		retrievedStack, stackRetrievalErr := common.GetStackByName(stackName, endpointSwarmClusterId, endpointId)
-		switch stackRetrievalErr.(type) {
+		if stackRetrievalErr == nil {
-		case nil:
 			// We are updating an existing stack
 			logrus.WithFields(logrus.Fields{
 				"stack": retrievedStack.Name,
@@ -110,7 +108,7 @@ var stackDeployCmd = &cobra.Command{
 			}).Info("Updating stack")
 			err := portainerClient.UpdateStack(retrievedStack, newEnvironmentVariables, stackFileContent, viper.GetBool("stack.deploy.prune"), endpointId)
 			common.CheckError(err)
-		case *common.StackNotFoundError:
+		} else if stackRetrievalErr == common.ErrStackNotFound {
 			// We are deploying a new stack
 			logrus.WithFields(logrus.Fields{
 				"stack": stackName,
@@ -149,7 +147,7 @@ var stackDeployCmd = &cobra.Command{
 					"id":       stack.ID,
 				}).Info("Stack created")
 			}
-		default:
+		} else {
 			// Something else happened
 			common.CheckError(stackRetrievalErr)
 		}

cmd/stackList.go

@@ -39,22 +39,21 @@ var stackListCmd = &cobra.Command{
 		if endpointId != 0 {
 			var selectionErr error
 			endpointSwarmClusterId, selectionErr = common.GetEndpointSwarmClusterId(endpointId)
-			switch selectionErr.(type) {
+			if selectionErr == nil {
-			case nil:
 				// It's a swarm cluster
 				logrus.WithFields(logrus.Fields{
 					"endpoint": endpointId,
 				}).Debug("Getting stacks")
 				stacks, err = portainerClient.GetStacks(endpointSwarmClusterId, endpointId)
 				common.CheckError(err)
-			case *common.StackClusterNotFoundError:
+			} else if selectionErr == common.ErrStackClusterNotFound {
 				// It's not a swarm cluster
 				logrus.WithFields(logrus.Fields{
 					"endpoint": endpointId,
 				}).Debug("Getting stacks")
 				stacks, err = portainerClient.GetStacks("", endpointId)
 				common.CheckError(err)
-			default:
+			} else {
 				// Something else happened
 				common.CheckError(selectionErr)
 			}

cmd/stackRemove.go

@@ -41,28 +41,26 @@ var stackRemoveCmd = &cobra.Command{
 
 		var selectionErr, stackRetrievalErr error
 		endpointSwarmClusterId, selectionErr = common.GetEndpointSwarmClusterId(endpointId)
-		switch selectionErr.(type) {
+		if selectionErr == nil {
-		case nil:
 			// It's a swarm cluster
 			logrus.WithFields(logrus.Fields{
 				"stack":    stackName,
 				"endpoint": endpointId,
 			}).Debug("Getting stack")
 			stack, stackRetrievalErr = common.GetStackByName(stackName, endpointSwarmClusterId, endpointId)
-		case *common.StackClusterNotFoundError:
+		} else if selectionErr == common.ErrStackClusterNotFound {
 			// It's not a swarm cluster
 			logrus.WithFields(logrus.Fields{
 				"stack":    stackName,
 				"endpoint": endpointId,
 			}).Debug("Getting stack")
 			stack, stackRetrievalErr = common.GetStackByName(stackName, "", endpointId)
-		default:
+		} else {
 			// Something else happened
 			common.CheckError(selectionErr)
 		}
 
-		switch stackRetrievalErr.(type) {
+		if stackRetrievalErr == nil {
-		case nil:
 			// The stack exists
 			stackId := stack.ID
 
@@ -76,7 +74,7 @@ var stackRemoveCmd = &cobra.Command{
 				"stack":    stack.Name,
 				"endpoint": stack.EndpointID,
 			}).Info("Stack removed")
-		case *common.StackNotFoundError:
+		} else if stackRetrievalErr == common.ErrStackNotFound {
 			// The stack does not exist
 			logrus.WithFields(logrus.Fields{
 				"stack":    stackName,
@@ -89,7 +87,7 @@ var stackRemoveCmd = &cobra.Command{
 					"suggestions": fmt.Sprintf("try with a different endpoint: psu stack rm %s --endpoint ENDPOINT_ID", stackName),
 				}).Fatal("stack does not exist")
 			}
-		default:
+		} else {
 			// Something else happened
 			common.CheckError(stackRetrievalErr)
 		}

common/utils.go

@@ -1,7 +1,6 @@
 package common
 
 import (
-	"errors"
 	"fmt"
 	"reflect"
 
@@ -9,6 +8,25 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+const (
+	ErrStackNotFound             = Error("Stack not found")
+	ErrStackClusterNotFound      = Error("Stack cluster not found")
+	ErrSeveralEndpointsAvailable = Error("Several endpoints available")
+	ErrNoEndpointsAvailable      = Error("No endpoints available")
+)
+
+const (
+	valueNotFoundError = Error("Value not found")
+)
+
+// Error represents an application error.
+type Error string
+
+// Error returns the error message.
+func (e Error) Error() string {
+	return string(e)
+}
+
 func GetDefaultEndpoint() (endpoint portainer.Endpoint, err error) {
 	portainerClient, err := GetClient()
 	if err != nil {
@@ -22,10 +40,10 @@ func GetDefaultEndpoint() (endpoint portainer.Endpoint, err error) {
 	}
 
 	if len(endpoints) == 0 {
-		err = errors.New("No endpoints available")
+		err = ErrNoEndpointsAvailable
 		return
 	} else if len(endpoints) > 1 {
-		err = errors.New("Several endpoints available")
+		err = ErrSeveralEndpointsAvailable
 		return
 	}
 	endpoint = endpoints[0]
@@ -49,9 +67,7 @@ func GetStackByName(name string, swarmId string, endpointId portainer.EndpointID
 			return stack, nil
 		}
 	}
-	err = &StackNotFoundError{
+	err = ErrStackNotFound
-		StackName: name,
-	}
 	return
 }
 
@@ -72,12 +88,11 @@ func GetEndpointSwarmClusterId(endpointId portainer.EndpointID) (endpointSwarmCl
 
 	// Get swarm (if any) information for endpoint
 	id, selectionErr := selectValue(result, []string{"Swarm", "Cluster", "ID"})
-	switch selectionErr.(type) {
+	if selectionErr == nil {
-	case nil:
 		endpointSwarmClusterId = id.(string)
-	case *valueNotFoundError:
+	} else if selectionErr == valueNotFoundError {
-		err = &StackClusterNotFoundError{}
+		err = ErrStackClusterNotFound
-	default:
+	} else {
 		err = selectionErr
 	}
 
@@ -87,7 +102,7 @@ func GetEndpointSwarmClusterId(endpointId portainer.EndpointID) (endpointSwarmCl
 func selectValue(jsonMap map[string]interface{}, jsonPath []string) (interface{}, error) {
 	value := jsonMap[jsonPath[0]]
 	if value == nil {
-		return nil, &valueNotFoundError{}
+		return nil, valueNotFoundError
 	} else if len(jsonPath) > 1 {
 		return selectValue(value.(map[string]interface{}), jsonPath[1:])
 	} else {
@@ -122,24 +137,3 @@ func repr(t reflect.Type, margin, beforeMargin string) (r string) {
 	}
 	return
 }
-
-// Custom customerrors
-type StackNotFoundError struct {
-	StackName string
-}
-
-func (e *StackNotFoundError) Error() string {
-	return fmt.Sprintf("Stack %s not found", e.StackName)
-}
-
-type valueNotFoundError struct{}
-
-func (e *valueNotFoundError) Error() string {
-	return "Value not found"
-}
-
-type StackClusterNotFoundError struct{}
-
-func (e *StackClusterNotFoundError) Error() string {
-	return "Stack cluster not found"
-}