A very simple terminal spinner
Working spinner (#1)
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-10
+2
codecov.yml
+2
codecov.yml
+78
-4
spin.go
+78
-4
spin.go
···
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// Package spin is a placeholder for something cool.
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// Package spin provides a simple, easy to use terminal spinner with configurable styles
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// to provide progress information in command line applications.
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package spin
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// Hello returns a welcome message for the project.
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func Hello() string {
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return "Hello spin"
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import (
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"fmt"
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"io"
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"sync"
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"sync/atomic"
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"time"
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)
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const (
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// frameRate is the rate at which spinner frames are rendered.
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frameRate = 100 * time.Millisecond
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// erase is the ANSI code for erasing the current line and resetting the cursor
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// position back to the start of the line.
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//
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// See https://gist.github.com/fnky/458719343aabd01cfb17a3a4f7296797#erase-functions.
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erase = "\r\x1b[K"
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)
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// Spinner contains the spinner state.
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type Spinner struct {
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w io.Writer // Where to draw the spinner
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stop chan struct{} // Signal for the spinner to stop
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msg string // Message to display during spinning e.g. "Loading"
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wg sync.WaitGroup // Manages the rendering goroutine
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running atomic.Bool // Whether the spinner is currently running
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}
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// New returns a new [Spinner].
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func New(w io.Writer, msg string) *Spinner {
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return &Spinner{
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w: w,
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stop: make(chan struct{}),
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msg: msg,
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}
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}
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// Start starts the spinner animation.
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func (s *Spinner) Start() {
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if s.running.Load() {
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// If it's already running, we have nothing to do
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return
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}
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s.running.Store(true)
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s.wg.Add(1)
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go func() {
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// Store the frames and the index locally so no need for synchronisation
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frames := [...]rune{'⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'}
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current := 0
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defer s.wg.Done()
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for {
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select {
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case <-s.stop:
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return
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case <-time.Tick(frameRate):
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fmt.Fprintf(s.w, "%s%c %s...", erase, frames[current], s.msg)
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current = (current + 1) % len(frames)
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}
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}
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}()
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}
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// Stop halts the spinner animation.
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func (s *Spinner) Stop() {
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if !s.running.Load() {
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// If it's not already running, there's nothing to do
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return
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}
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s.stop <- struct{}{} // Signal the stop
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s.wg.Wait() // Wait for the render goroutine to return
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s.running.Store(false)
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fmt.Fprint(s.w, erase) // Erase the line
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}
+24
-5
spin_test.go
+24
-5
spin_test.go
···
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package spin_test
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import (
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"bytes"
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"strings"
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"testing"
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"time"
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"github.com/FollowTheProcess/spin"
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)
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func TestHello(t *testing.T) {
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got := spin.Hello()
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want := "Hello spin"
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func TestSpinner(t *testing.T) {
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buf := &bytes.Buffer{}
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if got != want {
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t.Errorf("got %s, wanted %s", got, want)
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spinner := spin.New(buf, "Testing")
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spinner.Start()
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time.Sleep(300 * time.Millisecond)
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spinner.Stop()
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got := buf.String()
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frames := [...]rune{'⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'}
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found := false
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for _, frame := range frames {
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if strings.Contains(got, string(frame)) {
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found = true
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break
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}
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}
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if !found {
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t.Fatalf("expected output to contain a spinner frame:\n\n%s\n", got)
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}
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}
+19
examples/basic/main.go
+19
examples/basic/main.go
···
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package main
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import (
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"os"
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"time"
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"github.com/FollowTheProcess/spin"
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)
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const duration = 2 * time.Second
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func main() {
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spinner := spin.New(os.Stdout, "Digesting")
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spinner.Start()
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defer spinner.Stop()
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time.Sleep(duration)
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}