Make CLI functions return error instead of fatal out (#1379)

Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse 
the functions nor writing unit tests. This PR aims to make functions 
return errors instead of error out.

pkg/fission-cli/cmd/mqtrigger/create.go

@@ -26,9 +26,8 @@ import (
 	fv1 "github.com/fission/fission/pkg/apis/fission.io/v1"
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
 	"github.com/fission/fission/pkg/fission-cli/cmd/spec"
-	"github.com/fission/fission/pkg/fission-cli/log"
+	"github.com/fission/fission/pkg/fission-cli/util"
 	"github.com/fission/fission/pkg/types"
 )
 
@@ -38,8 +37,12 @@ type CreateSubCommand struct {
 }
 
 func Create(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := CreateSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }
@@ -59,7 +62,7 @@ func (opts *CreateSubCommand) complete(flags cli.Input) error {
 	}
 	fnName := flags.String("function")
 	if len(fnName) == 0 {
-		log.Fatal("Need a function name to create a trigger, use --function")
+		return errors.New("Need a function name to create a trigger, use --function")
 	}
 	fnNamespace := flags.String("fnNamespace")
 
@@ -73,23 +76,21 @@ func (opts *CreateSubCommand) complete(flags cli.Input) error {
 		mqType = types.MessageQueueTypeASQ
 	case types.MessageQueueTypeKafka:
 		mqType = types.MessageQueueTypeKafka
-
 	default:
-		log.Fatal("Unknown message queue type, currently only \"nats-streaming, azure-storage-queue, kafka \" is supported")
-
+		return errors.New("Unknown message queue type, currently only \"nats-streaming, azure-storage-queue, kafka \" is supported")
 	}
 
 	// TODO: check topic availability
 	topic := flags.String("topic")
 	if len(topic) == 0 {
-		log.Fatal("Topic cannot be empty")
+		return errors.New("Topic cannot be empty")
 	}
 	respTopic := flags.String("resptopic")
 
 	if topic == respTopic {
 		// TODO maybe this should just be a warning, perhaps
 		// allow it behind a --force flag
-		log.Fatal("Listen topic should not equal to response topic")
+		return errors.New("Listen topic should not equal to response topic")
 	}
 
 	errorTopic := flags.String("errortopic")
@@ -97,7 +98,7 @@ func (opts *CreateSubCommand) complete(flags cli.Input) error {
 	maxRetries := flags.Int("maxretries")
 
 	if maxRetries < 0 {
-		log.Fatal("Maximum number of retries must be a natural number, default is 0")
+		return errors.New("Maximum number of retries must be a natural number, default is 0")
 	}
 
 	contentType := flags.String("contenttype")

pkg/fission-cli/cmd/mqtrigger/delete.go

@@ -24,7 +24,7 @@ import (
 
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
+	"github.com/fission/fission/pkg/fission-cli/util"
 )
 
 type DeleteSubCommand struct {
@@ -33,8 +33,12 @@ type DeleteSubCommand struct {
 }
 
 func Delete(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := DeleteSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }
@@ -48,7 +52,7 @@ func (opts *DeleteSubCommand) do(flags cli.Input) error {
 }
 
 func (opts *DeleteSubCommand) complete(flags cli.Input) error {
-	m, err := cmd.GetMetadata("name", "triggerns", flags)
+	m, err := util.GetMetadata("name", "triggerns", flags)
 	if err != nil {
 		return err
 	}

pkg/fission-cli/cmd/mqtrigger/list.go

@@ -25,7 +25,7 @@ import (
 
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
+	"github.com/fission/fission/pkg/fission-cli/util"
 )
 
 type ListSubCommand struct {
@@ -34,8 +34,12 @@ type ListSubCommand struct {
 }
 
 func List(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := ListSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }

pkg/fission-cli/cmd/mqtrigger/update.go

@@ -24,7 +24,7 @@ import (
 	fv1 "github.com/fission/fission/pkg/apis/fission.io/v1"
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
+	"github.com/fission/fission/pkg/fission-cli/util"
 )
 
 type UpdateSubCommand struct {
@@ -33,8 +33,12 @@ type UpdateSubCommand struct {
 }
 
 func Update(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := UpdateSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }
@@ -48,7 +52,7 @@ func (opts *UpdateSubCommand) do(flags cli.Input) error {
 }
 
 func (opts *UpdateSubCommand) complete(flags cli.Input) error {
-	m, err := cmd.GetMetadata("name", "triggerns", flags)
+	m, err := util.GetMetadata("name", "triggerns", flags)
 	if err != nil {
 		return err
 	}