'set-default-builder' should suggest builders

commands/build.go

@@ -61,7 +61,7 @@ func Build(logger *logging.Logger, fetcher pack.Fetcher) *cobra.Command {
 			}
 
 			if bf.Config.DefaultBuilder == "" && buildFlags.Builder == "" {
-				suggestBuilders(logger)
+				suggestSettingBuilder(logger)
 				return MakeSoftError()
 			}
 
@@ -82,10 +82,14 @@ func Build(logger *logging.Logger, fetcher pack.Fetcher) *cobra.Command {
 	return cmd
 }
 
-func suggestBuilders(logger *logging.Logger) {
+func suggestSettingBuilder(logger *logging.Logger) {
 	logger.Info("Please select a default builder with:\n")
-	logger.Info("\tpack set-default-builder <builder image>")
-	logger.Info("\nSuggested builders:\n")
+	logger.Info("\tpack set-default-builder <builder image>\n")
+	suggestBuilders(logger)
+}
+
+func suggestBuilders(logger *logging.Logger) {
+	logger.Info("Suggested builders:\n")
 	tw := tabwriter.NewWriter(logger.RawWriter(), 10, 10, 5, ' ', tabwriter.TabIndent)
 	for len(suggestedBuilders) > 0 {
 		n := rand.Intn(len(suggestedBuilders))
@@ -96,7 +100,7 @@ func suggestBuilders(logger *logging.Logger) {
 		suggestedBuilders = append(suggestedBuilders[:n], suggestedBuilders[n+1:]...)
 	}
 	tw.Flush()
-	logger.Info("\n")
+	logger.Info("")
 	logger.Tip("Learn more about a specific builder with:\n")
 	logger.Info("\tpack inspect-builder [builder image]")
 }

commands/inspect_builder.go

@@ -24,7 +24,7 @@ func InspectBuilder(logger *logging.Logger, cfg *config.Config, inspector Builde
 		Args:  cobra.MaximumNArgs(1),
 		RunE: logError(logger, func(cmd *cobra.Command, args []string) error {
 			if cfg.DefaultBuilder == "" && len(args) == 0 {
-				suggestBuilders(logger)
+				suggestSettingBuilder(logger)
 				return MakeSoftError()
 			}
 

commands/inspect_builder_test.go

@@ -18,11 +18,11 @@ import (
 	h "github.com/buildpack/pack/testhelpers"
 )
 
-func TestCommands(t *testing.T) {
-	spec.Run(t, "Commands", testCommands, spec.Parallel(), spec.Report(report.Terminal{}))
+func TestInspectBuilderCommand(t *testing.T) {
+	spec.Run(t, "Commands", testInspectBuilderCommand, spec.Parallel(), spec.Report(report.Terminal{}))
 }
 
-func testCommands(t *testing.T, when spec.G, it spec.S) {
+func testInspectBuilderCommand(t *testing.T, when spec.G, it spec.S) {
 
 	var (
 		command        *cobra.Command

commands/run.go

@@ -36,7 +36,7 @@ func Run(logger *logging.Logger, fetcher pack.Fetcher) *cobra.Command {
 			}
 
 			if bf.Config.DefaultBuilder == "" && runFlags.BuildFlags.Builder == "" {
-				suggestBuilders(logger)
+				suggestSettingBuilder(logger)
 				return MakeSoftError()
 			}
 

commands/set_default_builder.go

@@ -1,19 +1,26 @@
 package commands
 
 import (
-	"github.com/spf13/cobra"
-
+	"fmt"
 	"github.com/buildpack/pack/config"
 	"github.com/buildpack/pack/logging"
 	"github.com/buildpack/pack/style"
+	"github.com/spf13/cobra"
 )
 
 func SetDefaultBuilder(logger *logging.Logger) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "set-default-builder <builder-name>",
 		Short: "Set default builder used by other commands",
-		Args:  cobra.ExactArgs(1),
+		Long: "Set default builder used by other commands.\n\n** For suggested builders simply leave builder name empty. **",
+		Args:  cobra.MaximumNArgs(1),
 		RunE: logError(logger, func(cmd *cobra.Command, args []string) error {
+			if len(args) < 1 || args[0] == "" {
+				logger.Info(fmt.Sprintf("Usage:\n\t%s\n", cmd.UseLine()))
+				suggestBuilders(logger)
+				return nil
+			}
+
 			cfg, err := config.NewDefault()
 			if err != nil {
 				return err
@@ -26,6 +33,7 @@ func SetDefaultBuilder(logger *logging.Logger) *cobra.Command {
 			return nil
 		}),
 	}
+
 	AddHelpFlag(cmd, "set-default-builder")
 	return cmd
 }

commands/set_default_builder_test.go

@@ -0,0 +1,50 @@
+package commands_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+	"github.com/spf13/cobra"
+
+	"github.com/buildpack/pack/commands"
+	"github.com/buildpack/pack/logging"
+	h "github.com/buildpack/pack/testhelpers"
+)
+
+func TestSetDefaultBuilder(t *testing.T) {
+	spec.Run(t, "Commands", testSetDefaultBuilderCommand, spec.Parallel(), spec.Report(report.Terminal{}))
+}
+
+func testSetDefaultBuilderCommand(t *testing.T, when spec.G, it spec.S) {
+
+	var (
+		command        *cobra.Command
+		logger         *logging.Logger
+		outBuf         bytes.Buffer
+	)
+
+	it.Before(func() {
+		logger = logging.NewLogger(&outBuf, &outBuf, false, false)
+		command = commands.SetDefaultBuilder(logger)
+	})
+
+	when("#SetDefaultBuilder", func() {
+		when("no builder provided", func() {
+			it("display suggested builders", func() {
+				command.SetArgs([]string{})
+				h.AssertNil(t, command.Execute())
+				h.AssertContains(t, outBuf.String(), "Suggested builders:")
+			})
+		})
+
+		when("empty builder name is provided", func() {
+			it("display suggested builders", func() {
+				command.SetArgs([]string{})
+				h.AssertNil(t, command.Execute())
+				h.AssertContains(t, outBuf.String(), "Suggested builders:")
+			})
+		})
+	})
+}