(GH-15) Add prm set backend command

This commit adds the `prm set backend` command and some minor
refactoring of existing set command functionality and the `config`
package.

cmd/set/backend.go

@@ -0,0 +1,48 @@
+package set
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/puppetlabs/prm/pkg/prm"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+var SelectedBackend prm.BackendType
+
+func (sc *SetCommand) createSetBackendCommand() *cobra.Command {
+	tmp := &cobra.Command{
+		Use:       "backend <BACKEND>",
+		Short:     "Sets the backend exec environment to the specified type",
+		Long:      `Sets the backend exec environment to the specified type`,
+		PreRunE:   sc.setBackendPreRunE,
+		RunE:      sc.setBackendType,
+		ValidArgs: []string{string(prm.DOCKER)},
+	}
+
+	return tmp
+}
+
+func (sc *SetCommand) setBackendPreRunE(cmd *cobra.Command, args []string) (err error) {
+	if len(args) > 1 {
+		return fmt.Errorf("too many args, please specify ONE of the following backend types after 'set backend':\n- %s", prm.DOCKER)
+	}
+
+	if len(args) < 1 {
+		return fmt.Errorf("please specify specify one of the following backend types after 'set backend':\n- %s", prm.DOCKER)
+	}
+
+	switch strings.ToLower(args[0]) {
+	case string(prm.DOCKER):
+		SelectedBackend = prm.DOCKER
+	default:
+		return fmt.Errorf("'%s' is not a valid backend type, please specify one of the following backend types:\n- %s", args[0], prm.DOCKER)
+	}
+
+	return nil
+}
+
+func (sc *SetCommand) setBackendType(cmd *cobra.Command, args []string) error {
+	return sc.Utils.SetAndWriteConfig(prm.BackendCfgKey, string(SelectedBackend))
+}

cmd/set/set.go

@@ -9,17 +9,20 @@ import (
 
 func CreateSetCommand() *cobra.Command {
 	tmp := &cobra.Command{
+		// TODO: Add Backend as valid arg
 		Use:                   fmt.Sprintf("set %s", prm.PuppetCmdFlag),
 		Short:                 "Sets the specified configuration to the specified value",
 		Long:                  "Sets the specified configuration to the specified value",
 		DisableFlagsInUseLine: true,
+		// TODO: Add Backend as valid arg		
 		ValidArgs:             []string{prm.PuppetCmdFlag},
 		Run: func(cmd *cobra.Command, args []string) {
 			cmd.HelpFunc()(cmd, args)
 		},
 	}
 
 	tmp.AddCommand(createSetPuppetCommand())
+	tmp.AddCommand(createSetBackendCommand())
 
 	return tmp
 }

cmd/set/set_test.go

@@ -2,18 +2,20 @@ package set_test
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
 	"testing"
 
 	"github.com/puppetlabs/prm/cmd/set"
+	"github.com/puppetlabs/prm/pkg/prm"
 	"github.com/stretchr/testify/assert"
 )
 
 type test struct {
-	name              string
-	args              []string
-	expectedOutput    string
-	expectedPuppetVer string
+(??)	name              string
+(??)	args              []string
+(??)	expectedErrMsg    string
+(??)	expectedPuppetVer string
 	expectError       bool
 }
 
@@ -69,6 +71,37 @@ func Test_SetPuppetCommand(t *testing.T) {
 	execTests(t, tests)
 }
 
+func Test_SetBackendCommand(t *testing.T) {
+	tests := []test{
+		{
+			name:               "Should handle valid backend selection (docker)",
+			args:               []string{"backend", "docker"},
+			expectedBackedType: prm.DOCKER,
+		},
+		{
+			name:               "Should handle valid backend selection (dOcKeR)",
+			args:               []string{"backend", "dOcKeR"},
+			expectedBackedType: prm.DOCKER,
+		},
+		{
+			name:           "Should error when too many args supplied to 'backend' sub cmd",
+			args:           []string{"backend", "foo", "bar"},
+			expectedErrMsg: fmt.Sprintf("Error: too many args, please specify ONE of the following backend types after 'set backend':\n- %s", prm.DOCKER),
+		},
+		{
+			name:           "Should error when no arg supplied to 'badckend' sub cmd",
+			args:           []string{"backend"},
+			expectedErrMsg: fmt.Sprintf("please specify specify one of the following backend types after 'set backend':\n- %s", prm.DOCKER),
+		},
+		{
+			name:           "Should error when invalid backend type supplied to 'badckend' sub cmd",
+			args:           []string{"backend", "foo"},
+			expectedErrMsg: fmt.Sprintf("Error: 'foo' is not a valid backend type, please specify one of the following backend types:\n- %s", prm.DOCKER),
+		},
+	}
+	execTests(t, tests)
+}
+
 func execTests(t *testing.T, tests []test) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -91,11 +124,24 @@ func execTests(t *testing.T, tests []test) {
 				return
 			}
 
-			if tt.expectedPuppetVer != "" {
-				if set.PuppetSemVer.String() != tt.expectedPuppetVer {
-					t.Errorf("Normalised Puppet version (%s) did not match expected version (%s)", set.PuppetSemVer.String(), tt.expectedPuppetVer)
-				}
-			}
+			validatePuppetVer(t, tt)
+			validateBackendType(t, tt)
 		})
 	}
 }
+
+func validatePuppetVer(t *testing.T, tt test) {
+	if tt.expectedPuppetVer != "" {
+		if set.PuppetSemVer.String() != tt.expectedPuppetVer {
+			t.Errorf("Normalised Puppet version (%s) did not match expected version (%s)", set.PuppetSemVer.String(), tt.expectedPuppetVer)
+		}
+	}
+}
+
+func validateBackendType(t *testing.T, tt test) {
+	if tt.expectedBackedType != "" {
+		if set.SelectedBackend != tt.expectedBackedType {
+			t.Errorf("Normalised Backend type (%s) did not match expected backend type (%s)", set.SelectedBackend, tt.expectedBackedType)
+		}
+	}
+}

pkg/prm/backend.go

@@ -1,6 +1,12 @@
 //nolint:structcheck,unused
 package prm
 
+type BackendType string
+
+const (
+	DOCKER BackendType = "docker"
+)
+
 type BackendI interface {
 	GetTool(toolName string, prmConfig Config) (Tool, error)
 	Validate(tool *Tool) (ToolExitCode, error)

pkg/prm/config.go

@@ -12,6 +12,7 @@ const (
 	PuppetCmdFlag    string = "puppet"
 	PuppetVerCfgKey  string = "puppet.version"
 	DefaultPuppetVer string = "7"
+	BackendCfgKey   string = "backend.type"
 )
 
 type Config struct {