feat(spinner): add Output method to expose overwriting the output

spinner/spinner.go

@@ -90,6 +90,12 @@ func (s *Spinner) Accessible(accessible bool) *Spinner {
 	return s
 }
 
+// Output sets the output of the spinner.
+func (s *Spinner) Output(output *termenv.Output) *Spinner {
+	s.output = output
+	return s
+}
+
 // New creates a new spinner.
 func New() *Spinner {
 	s := spinner.New()
@@ -174,7 +180,7 @@ func (s *Spinner) runAccessible() error {
 	s.output.HideCursor()
 	frame := s.spinner.Style.Render("...")
 	title := s.titleStyle.Render(strings.TrimSuffix(s.title, "..."))
-	fmt.Println(title + frame)
+	fmt.Fprintln(s.output, title+frame)
 
 	if s.ctx == nil {
 		s.action()

spinner/spinner_test.go

@@ -2,13 +2,18 @@ package spinner
 
 import (
 	"context"
+	"errors"
+	"io"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/charmbracelet/bubbles/spinner"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
+	"github.com/muesli/termenv"
 )
 
 func TestNewSpinner(t *testing.T) {
@@ -112,3 +117,86 @@ func TestAccessibleSpinner(t *testing.T) {
 		t.Errorf("Run() in accessible mode returned an error: %v", err)
 	}
 }
+
+func TestSpinnerOutput(t *testing.T) {
+	tests := []struct {
+		name       string
+		wantStdout bool
+		wantStderr bool
+	}{
+		{
+			name:       "stdout",
+			wantStdout: true,
+			wantStderr: false,
+		},
+		{
+			name:       "stderr",
+			wantStdout: false,
+			wantStderr: true,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			const title = "Test Output"
+
+			// Save original stderr and stdout
+			oldStderr := os.Stderr
+			oldStdout := os.Stdout
+
+			// Create pipes for stderr and stdout
+			stderrReader, stderrWriter, _ := os.Pipe()
+			stdoutReader, stdoutWriter, _ := os.Pipe()
+
+			// Set global stderr and stdout to our pipes
+			os.Stderr = stderrWriter
+			os.Stdout = stdoutWriter
+
+			// Create a spinner and set its output
+			s := New().Title(title).Accessible(true)
+			if tc.wantStderr {
+				s.Output(termenv.NewOutput(os.Stderr))
+			}
+			if tc.wantStdout {
+				s.Output(termenv.NewOutput(os.Stdout))
+			}
+			s.action = func() { time.Sleep(100 * time.Millisecond) }
+			if err := s.Run(); err != nil {
+				t.Errorf("Spinner.Run() returned an error: %v", err)
+			}
+
+			// Restore original stderr and stdout
+			os.Stderr = oldStderr
+			os.Stdout = oldStdout
+
+			// Close the pipes
+			if err := errors.Join(stderrWriter.Close(), stdoutWriter.Close()); err != nil {
+				t.Errorf("Failed to close pipes: %v", err)
+			}
+
+			// Read from the pipes
+			stderrOutput, stderrErr := io.ReadAll(stderrReader)
+			stdoutOutput, stdoutErr := io.ReadAll(stdoutReader)
+			if err := errors.Join(stderrErr, stdoutErr); err != nil {
+				t.Errorf("Failed to read from pipes: %v", err)
+			}
+
+			// Check the output
+			if tc.wantStderr {
+				if !strings.Contains(string(stderrOutput), title) {
+					t.Errorf("Stderr got %q, but wanted %q", stderrOutput, title)
+				}
+				if len(stdoutOutput) > 0 {
+					t.Errorf("Expected no output on stdout, but got %q", stdoutOutput)
+				}
+			}
+			if tc.wantStdout {
+				if !strings.Contains(string(stdoutOutput), title) {
+					t.Errorf("Stdout got %q, but wanted %q", stdoutOutput, title)
+				}
+				if len(stderrOutput) > 0 {
+					t.Errorf("Expected no output on stderr, but got %q", stderrOutput)
+				}
+			}
+		})
+	}
+}