move output format decision outside command

Author: Massimiliano Pippi

Diff for: cli/board/details.go

@@ -23,7 +23,6 @@ import (
 
 	"github.com/arduino/arduino-cli/cli/errorcodes"
 	"github.com/arduino/arduino-cli/cli/feedback"
-	"github.com/arduino/arduino-cli/cli/globals"
 	"github.com/arduino/arduino-cli/cli/instance"
 	"github.com/arduino/arduino-cli/commands/board"
 	rpc "github.com/arduino/arduino-cli/rpc/commands"
@@ -52,14 +51,21 @@ func runDetailsCommand(cmd *cobra.Command, args []string) {
 		os.Exit(errorcodes.ErrGeneric)
 	}
 
-	if globals.OutputFormat == "json" {
-		feedback.PrintJSON(res)
-	} else {
-		outputDetailsResp(res)
-	}
+	feedback.PrintResult(detailsResult{details: res})
+}
+
+// ouput from this command requires special formatting, let's create a dedicated
+// feedback.Result implementation
+type detailsResult struct {
+	details *rpc.BoardDetailsResp
+}
+
+func (dr detailsResult) Data() interface{} {
+	return dr.details
 }
 
-func outputDetailsResp(details *rpc.BoardDetailsResp) {
+func (dr detailsResult) String() string {
+	details := dr.details
 	// Table is 4 columns wide:
 	// |               |                             | |                       |
 	// Board name:     Arduino Nano
@@ -104,5 +110,5 @@ func outputDetailsResp(details *rpc.BoardDetailsResp) {
 		}
 	}
 
-	feedback.Print(t.Render())
+	return t.Render()
 }

Diff for: cli/cli.go

@@ -101,11 +101,13 @@ func toLogLevel(s string) (t logrus.Level, found bool) {
 	return
 }
 
-func isValidFormat(arg string) bool {
-	return map[string]bool{
-		"json": true,
-		"text": true,
+func parseFormatString(arg string) (feedback.OutputFormat, bool) {
+	f, found := map[string]feedback.OutputFormat{
+		"json": feedback.JSON,
+		"text": feedback.Text,
 	}[arg]
+
+	return f, found
 }
 
 func preRun(cmd *cobra.Command, args []string) {
@@ -141,9 +143,12 @@ func preRun(cmd *cobra.Command, args []string) {
 	}
 
 	// check the right format was passed
-	if !isValidFormat(globals.OutputFormat) {
+	if f, found := parseFormatString(globals.OutputFormat); !found {
 		feedback.Error("Invalid output format: " + globals.OutputFormat)
 		os.Exit(errorcodes.ErrBadCall)
+	} else {
+		// use the format to configure the Feedback
+		feedback.SetFormat(f)
 	}
 
 	globals.InitConfigs()

Diff for: cli/feedback/exported.go

@@ -29,6 +29,11 @@ func SetDefaultFeedback(f *Feedback) {
 	fb = f
 }
 
+// SetFormat can be used to change the output format at runtime
+func SetFormat(f OutputFormat) {
+	fb.SetFormat(f)
+}
+
 // OutputWriter returns the underlying io.Writer to be used when the Print*
 // api is not enough
 func OutputWriter() io.Writer {
@@ -68,3 +73,8 @@ func Error(v ...interface{}) {
 func PrintJSON(v interface{}) {
 	fb.PrintJSON(v)
 }
+
+// PrintResult is a convenient wrapper...
+func PrintResult(res Result) {
+	fb.PrintResult(res)
+}

Diff for: cli/feedback/feedback.go

@@ -24,24 +24,48 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// OutputFormat is used to determine the output format
+type OutputFormat int
+
+const (
+	// Text means plain text format, suitable for ansi terminals
+	Text OutputFormat = iota
+	// JSON means JSON format
+	JSON
+)
+
+// Result is anything more complex than a sentence that needs to be printed
+// for the user.
+type Result interface {
+	fmt.Stringer
+	Data() interface{}
+}
+
 // Feedback wraps an io.Writer and provides an uniform API the CLI can use to
 // provide feedback to the users.
 type Feedback struct {
-	out io.Writer
-	err io.Writer
+	out    io.Writer
+	err    io.Writer
+	format OutputFormat
 }
 
 // New creates a Feedback instance
-func New(out, err io.Writer) *Feedback {
+func New(out, err io.Writer, format OutputFormat) *Feedback {
 	return &Feedback{
-		out: out,
-		err: err,
+		out:    out,
+		err:    err,
+		format: format,
 	}
 }
 
 // DefaultFeedback provides a basic feedback object to be used as default.
 func DefaultFeedback() *Feedback {
-	return New(os.Stdout, os.Stderr)
+	return New(os.Stdout, os.Stderr, Text)
+}
+
+// SetFormat can be used to change the output format at runtime
+func (fb *Feedback) SetFormat(f OutputFormat) {
+	fb.format = f
 }
 
 // OutputWriter returns the underlying io.Writer to be used when the Print*
@@ -88,3 +112,16 @@ func (fb *Feedback) PrintJSON(v interface{}) {
 		fb.Print(string(d))
 	}
 }
+
+// PrintResult is a convenient wrapper...
+func (fb *Feedback) PrintResult(res Result) {
+	if fb.format == JSON {
+		if d, err := json.MarshalIndent(res.Data(), "", "  "); err != nil {
+			fb.Errorf("Error during JSON encoding of the output: %v", err)
+		} else {
+			fb.Print(string(d))
+		}
+	} else {
+		fb.Print(fmt.Sprintf("%s", res))
+	}
+}