Support for multi-line spinner strings (#146)

Author: Guillaume Bouvignies

_example/main.go

@@ -3,6 +3,7 @@ package main
 
 import (
 	"log"
+	"strings"
 	"time"
 
 	"github.com/briandowns/spinner"
@@ -22,6 +23,13 @@ func main() {
 	s.Suffix = " :appended text" // Append text after the spinner
 	time.Sleep(4 * time.Second)
 
+	s.Suffix = " :appended " + strings.Repeat("very long text ", 20) // Append very long text
+	time.Sleep(4 * time.Second)
+
+	s.Suffix = " :appended multi \nline\nsuffix\ntext" // Append multi line text
+	time.Sleep(4 * time.Second)
+
+	s.Suffix = " :appended text" // Append text after the spinner
 	s.Prefix = "Colors: "
 
 	if err := s.Color("yellow"); err != nil {

go.mod

@@ -6,4 +6,5 @@ require (
 	github.com/fatih/color v1.7.0
 	github.com/mattn/go-colorable v0.1.2 // indirect
 	github.com/mattn/go-isatty v0.0.8
+	golang.org/x/term v0.1.0
 )

go.sum

@@ -4,5 +4,8 @@ github.com/mattn/go-colorable v0.1.2 h1:/bC9yWikZXAL9uJdulbSfyVNIR3n3trXl+v8+1sx
 github.com/mattn/go-colorable v0.1.2/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-isatty v0.0.8 h1:HLtExJ+uU2HOZ+wI0Tt5DtUDrx8yhUqDcp7fYERX4CE=
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
-golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223 h1:DH4skfRX4EBpamg7iV4ZlCpblAHI6s6TDM39bFZumv8=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 h1:SrN+KX8Art/Sf4HNj6Zcz06G7VEz+7w9tdXTPOZ7+l4=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.1.0 h1:g6Z6vPFA9dYBAF7DWcH6sCcOntplXsDKcliusYijMlw=
+golang.org/x/term v0.1.0/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=

spinner.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math"
 	"os"
 	"runtime"
 	"strconv"
@@ -29,6 +30,7 @@ import (
 
 	"github.com/fatih/color"
 	"github.com/mattn/go-isatty"
+	"golang.org/x/term"
 )
 
 // errInvalidColor is returned when attempting to set an invalid color
@@ -439,13 +441,23 @@ func (s *Spinner) erase() {
 		return
 	}
 
+	numberOfLinesToErase := computeNumberOfLinesNeededToPrintString(s.lastOutputPlain)
+
 	// Taken from https://en.wikipedia.org/wiki/ANSI_escape_code:
 	// \r     - Carriage return - Moves the cursor to column zero
 	// \033[K - Erases part of the line. If n is 0 (or missing), clear from
 	// cursor to the end of the line. If n is 1, clear from cursor to beginning
 	// of the line. If n is 2, clear entire line. Cursor position does not
 	// change.
-	fmt.Fprintf(s.Writer, "\r\033[K")
+	// \033[F - Go to the beginning of previous line
+	eraseCodeString := strings.Builder{}
+	// current position is at the end of the last printed line. Start by erasing current line
+	eraseCodeString.WriteString("\r\033[K") // start by erasing current line
+	for i := 1; i < numberOfLinesToErase; i++ {
+		// For each additional lines, go up one line and erase it.
+		eraseCodeString.WriteString("\033[F\033[K")
+	}
+	fmt.Fprintf(s.Writer, eraseCodeString.String())
 	s.lastOutputPlain = ""
 }
 
@@ -473,3 +485,29 @@ func GenerateNumberSequence(length int) []string {
 func isRunningInTerminal() bool {
 	return isatty.IsTerminal(os.Stdout.Fd())
 }
+
+func computeNumberOfLinesNeededToPrintString(linePrinted string) int {
+	terminalWidth := math.MaxInt // assume infinity by default to keep behaviour consistent with what we had before
+	if term.IsTerminal(0) {
+		if width, _, err := term.GetSize(0); err == nil {
+			terminalWidth = width
+		}
+	}
+	return computeNumberOfLinesNeededToPrintStringInternal(linePrinted, terminalWidth)
+}
+
+func computeNumberOfLinesNeededToPrintStringInternal(linePrinted string, maxLineWidth int) int {
+	if linePrinted == "" {
+		// empty string will necessarily take one line
+		return 1
+	}
+	idxOfNewline := strings.Index(linePrinted, "\n")
+	if idxOfNewline < 0 {
+		// we use utf8.RunCountInString() in place of len() because the string contains "complex" unicode chars that
+		// might be represented by multiple individual bytes (typically spinner char)
+		return int(math.Ceil(float64(utf8.RuneCountInString(linePrinted)) / float64(maxLineWidth)))
+	} else {
+		return computeNumberOfLinesNeededToPrintStringInternal(linePrinted[:idxOfNewline], maxLineWidth) +
+			computeNumberOfLinesNeededToPrintStringInternal(linePrinted[idxOfNewline+1:], maxLineWidth)
+	}
+}

spinner_test.go

@@ -20,6 +20,7 @@ import (
 	"io/ioutil"
 	"os"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -280,6 +281,60 @@ func TestWithWriter(t *testing.T) {
 	_ = s
 }
 
+func TestComputeNumberOfLinesNeededToPrintStringInternal_SingleLine(t *testing.T) {
+	line := "Hello world"
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 1
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' line, got '%d'", line, expectedResult, result)
+	}
+}
+
+func TestComputeNumberOfLinesNeededToPrintStringInternal_MultiLine(t *testing.T) {
+	line := "Hello\n world"
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 2
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' lines, got '%d'", line, expectedResult, result)
+	}
+}
+
+func TestComputeNumberOfLinesPrinted_LongString(t *testing.T) {
+	line := "Hello world! I am a super long string that will be printed in 2 lines"
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 2
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' lines, got '%d'", line, expectedResult, result)
+	}
+}
+
+func TestComputeNumberOfLinesNeededToPrintStringInternal_LongStringWithNewlines(t *testing.T) {
+	line := "Hello world!\nI am a super long string that will be printed in 2 lines.\nAnother new line"
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 4
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' lines, got '%d'", line, expectedResult, result)
+	}
+}
+
+func TestComputeNumberOfLinesNeededToPrintStringInternal_NewlineCharAtTheEnd(t *testing.T) {
+	line := "Hello world!\n"
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 2
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' lines, got '%d'", line, expectedResult, result)
+	}
+}
+
+func TestComputeNumberOfLinesNeededToPrintStringInternal_StringExactlyTheSizeOfTheScreen(t *testing.T) {
+	line := strings.Repeat("a", 50)
+	result := computeNumberOfLinesNeededToPrintStringInternal(line, 50)
+	expectedResult := 1
+	if result != expectedResult {
+		t.Errorf("Line '%s' shoud be printed on '%d' lines, got '%d'", line, expectedResult, result)
+	}
+}
+
 /*
 Benchmarks
 */