feat(spin): Add support for --show-error for the spinner.

This makes it so that if the `--show-error` flag is provided then the
full output of the command will be printed if the command fails. This
kind of works in conjuncture with `--show-output` in that if the command
succeeds only STDOUT is pushed. If the command fails both `STDOUT` and
`STDERR` are pushed.

This builds off of charmbracelet#371

Resolves charmbracelet#55

spin/command.go

@@ -44,15 +44,26 @@ func (o Options) Run() error {
 		return fmt.Errorf("failed to access stdout: %w", err)
 	}
 
-	if o.ShowOutput {
-		// BubbleTea writes the View() to stderr.
-		// If the program is being piped then put the accumulated output in stdout.
-		if !isTTY {
-			_, err := os.Stdout.WriteString(m.stdout)
-			if err != nil {
-				return fmt.Errorf("failed to write to stdout: %w", err)
+	// If the command succeed, and we are printing output and we are in a TTY then push the STDOUT we got
+	// to the actual STDOUT for piping or other things.
+	if m.status == 0 {
+		if o.ShowOutput {
+			// BubbleTea writes the View() to stderr.
+			// If the program is being piped then put the accumulated output in stdout.
+			if !isTTY {
+				_, err := os.Stdout.WriteString(m.stdout)
+				if err != nil {
+					return fmt.Errorf("failed to write to stdout: %w", err)
+				}
 			}
 		}
+	} else if o.ShowError {
+		// Otherwise if we are showing errors and the command did not exit with a 0 status code then push all of the command
+		// output to the terminal. This way failed commands can be debugged.
+		_, err := os.Stdout.WriteString(m.output)
+		if err != nil {
+			return fmt.Errorf("failed to write to stdout: %w", err)
+		}
 	}
 
 	os.Exit(m.status)

spin/options.go

@@ -11,6 +11,7 @@ type Options struct {
 	Command []string `arg:"" help:"Command to run"`
 
 	ShowOutput   bool          `help:"Show or pipe output of command during execution" default:"false" env:"GUM_SPIN_SHOW_OUTPUT"`
+	ShowError    bool          `help:"Show output of command only if the command fails" default:"false" env:"GUM_SPIN_SHOW_ERROR"`
 	Spinner      string        `help:"Spinner type" short:"s" type:"spinner" enum:"line,dot,minidot,jump,pulse,points,globe,moon,monkey,meter,hamburger" default:"dot" env:"GUM_SPIN_SPINNER"`
 	SpinnerStyle style.Styles  `embed:"" prefix:"spinner." set:"defaultForeground=212" envprefix:"GUM_SPIN_SPINNER_"`
 	Title        string        `help:"Text to display to user while spinning" default:"Loading..." env:"GUM_SPIN_TITLE"`

spin/spin.go

@@ -15,6 +15,7 @@
 package spin
 
 import (
+	"io"
 	"os"
 	"os/exec"
 	"strings"
@@ -37,16 +38,22 @@ type model struct {
 	aborted    bool
 	status     int
 	stdout     string
+	stderr     string
+	output     string
 	showOutput bool
+	showError  bool
 	timeout    time.Duration
 	hasTimeout bool
 }
 
+var bothbuf strings.Builder
 var outbuf strings.Builder
 var errbuf strings.Builder
 
 type finishCommandMsg struct {
 	stdout string
+	stderr string
+	output string
 	status int
 }
 
@@ -59,8 +66,11 @@ func commandStart(command []string) tea.Cmd {
 		cmd := exec.Command(command[0], args...) //nolint:gosec
 
 		if isatty.IsTerminal(os.Stdout.Fd()) {
-			cmd.Stdout = &outbuf
-			cmd.Stderr = &errbuf
+			stdout := io.MultiWriter(&bothbuf, &errbuf)
+			stderr := io.MultiWriter(&bothbuf, &outbuf)
+
+			cmd.Stdout = stdout
+			cmd.Stderr = stderr
 		} else {
 			cmd.Stdout = os.Stdout
 		}
@@ -75,6 +85,8 @@ func commandStart(command []string) tea.Cmd {
 
 		return finishCommandMsg{
 			stdout: outbuf.String(),
+			stderr: errbuf.String(),
+			output: bothbuf.String(),
 			status: status,
 		}
 	}
@@ -123,6 +135,8 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		return m, timeout.Tick(msg.TimeoutValue, msg.Data)
 	case finishCommandMsg:
 		m.stdout = msg.stdout
+		m.stderr = msg.stderr
+		m.output = msg.output
 		m.status = msg.status
 		m.quitting = true
 		return m, tea.Quit