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12 changes: 11 additions & 1 deletion internal/cmdutil/iostreams.go
Original file line number Diff line number Diff line change
Expand Up @@ -18,17 +18,26 @@ type IOStreams struct {
Out io.Writer
ErrOut io.Writer
IsTerminal bool
// ErrIsTerminal reports whether ErrOut is an interactive terminal. Use it to
// gate stderr-only animations (spinners) so pipes / CI / captured stderr stay
// clean. Derived from ErrOut's underlying *os.File; non-file writers → false.
ErrIsTerminal bool
}

// NewIOStreams builds an IOStreams from arbitrary readers/writers.
// IsTerminal is derived from in's underlying *os.File, if any; non-file
// readers (bytes.Buffer, strings.Reader, …) yield IsTerminal=false.
// ErrIsTerminal is derived the same way from errOut.
func NewIOStreams(in io.Reader, out, errOut io.Writer) *IOStreams {
isTerminal := false
if f, ok := in.(*os.File); ok {
isTerminal = term.IsTerminal(int(f.Fd()))
}
return &IOStreams{In: in, Out: out, ErrOut: errOut, IsTerminal: isTerminal}
errIsTerminal := false
if f, ok := errOut.(*os.File); ok {
errIsTerminal = term.IsTerminal(int(f.Fd()))
}
return &IOStreams{In: in, Out: out, ErrOut: errOut, IsTerminal: isTerminal, ErrIsTerminal: errIsTerminal}
}

// SystemIO creates an IOStreams wired to the process's standard file descriptors.
Expand Down Expand Up @@ -57,6 +66,7 @@ func normalizeStreams(s *IOStreams) *IOStreams {
}
if out.ErrOut == nil {
out.ErrOut = sys.ErrOut
out.ErrIsTerminal = sys.ErrIsTerminal
}
}
return &out
Expand Down
80 changes: 80 additions & 0 deletions internal/output/spinner.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,80 @@
// Copyright (c) 2026 Lark Technologies Pte. Ltd.
// SPDX-License-Identifier: MIT

package output

import (
"fmt"
"io"
"sync"
"time"
)

// spinnerFrames are braille spinner glyphs cycled to animate progress.
var spinnerFrames = []string{"⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"}

const (
spinnerInterval = 80 * time.Millisecond
spinnerHideCursor = "\x1b[?25l"
spinnerShowCursor = "\x1b[?25h"
spinnerClearLine = "\r\x1b[K" // CR + clear-to-end-of-line
)

// StartSpinner renders a braille spinner with an elapsed-seconds counter to w
// until the returned stop() is called, e.g.:
//
// ⠹ Publishing dev → main... 3s
//
// It is meant for slow operations (long polls, first-time provisioning) so the
// user sees the CLI is alive. Always write to STDERR (w = IO().ErrOut) so the
// animation never pollutes stdout — the JSON/pretty result stays clean.
//
// When enabled is false (stderr is not a TTY: pipes, CI, captured output) it is
// a no-op returning a no-op stop, so non-interactive runs emit nothing. Gate on
// the stderr-TTY check (IOStreams.ErrIsTerminal), not the output format: the
// spinner is stderr-only and self-clears, so it is shown in JSON mode too.
//
// stop() clears the spinner line, restores the cursor, and blocks until the
// render goroutine has finished — so callers can safely write the result to
// stdout/stderr immediately after. Call stop() BEFORE printing the result, and
// it is safe to call more than once (e.g. an explicit call plus a defer).
func StartSpinner(w io.Writer, enabled bool, label string) func() {
if !enabled || w == nil {
return func() {}
}

done := make(chan struct{})
finished := make(chan struct{})
start := time.Now()

go func() {
defer close(finished)
frame := 0
fmt.Fprint(w, spinnerHideCursor)
render := func() {
elapsed := int(time.Since(start).Seconds())
fmt.Fprintf(w, "%s%s %s... %ds", spinnerClearLine, spinnerFrames[frame], label, elapsed)
frame = (frame + 1) % len(spinnerFrames)
}
render()
ticker := time.NewTicker(spinnerInterval)
defer ticker.Stop()
for {
select {
case <-done:
fmt.Fprint(w, spinnerClearLine+spinnerShowCursor)
return
case <-ticker.C:
render()
}
}
}()

var once sync.Once
return func() {
once.Do(func() {
close(done)
<-finished // wait for the line to be cleared before returning
})
}
}
54 changes: 54 additions & 0 deletions internal/output/spinner_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
// Copyright (c) 2026 Lark Technologies Pte. Ltd.
// SPDX-License-Identifier: MIT

package output

import (
"bytes"
"strings"
"testing"
)

// TestStartSpinner_DisabledIsNoop asserts that a disabled spinner writes nothing and its stop func is idempotent.
func TestStartSpinner_DisabledIsNoop(t *testing.T) {
var buf bytes.Buffer
stop := StartSpinner(&buf, false, "working")
stop()
stop() // idempotent
if buf.Len() != 0 {
t.Fatalf("disabled spinner wrote %q, want nothing", buf.String())
}
}

// TestStartSpinner_NilWriterIsNoop asserts that a nil writer is a no-op and stopping does not panic.
func TestStartSpinner_NilWriterIsNoop(t *testing.T) {
stop := StartSpinner(nil, true, "working")
stop() // must not panic
}

// TestStartSpinner_EnabledAnimatesAndCleansUp asserts that an enabled spinner renders a frame and label, then clears the line and restores the cursor on stop.
func TestStartSpinner_EnabledAnimatesAndCleansUp(t *testing.T) {
var buf bytes.Buffer
stop := StartSpinner(&buf, true, "Publishing")
// The goroutine renders the first frame synchronously before selecting on
// the stop channel, so even an immediate stop() yields one full cycle.
stop()
stop() // idempotent, must not panic or double-write after finished

out := buf.String()
if !strings.Contains(out, spinnerHideCursor) {
t.Errorf("missing hide-cursor escape:\n%q", out)
}
if !strings.Contains(out, spinnerFrames[0]) {
t.Errorf("missing first spinner frame %q:\n%q", spinnerFrames[0], out)
}
if !strings.Contains(out, "Publishing...") {
t.Errorf("missing label:\n%q", out)
}
if !strings.Contains(out, spinnerClearLine) {
t.Errorf("missing clear-line escape:\n%q", out)
}
if !strings.HasSuffix(out, spinnerShowCursor) {
t.Errorf("must end by restoring the cursor:\n%q", out)
}
}
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