termstatus: test status line sanitization

changelog/unreleased/pull-4318

@@ -0,0 +1,8 @@
+Bugfix: Correctly clean up status bar output of the `backup` command
+
+Due to a regression in restic 0.15.2, the status bar of the `backup` command
+could leave some output behind. This happened if filenames were printed that
+are wider than the current terminal width. This has been fixed.
+
+https://github.com/restic/restic/issues/4319
+https://github.com/restic/restic/pull/4318

internal/ui/termstatus/status.go

@@ -334,6 +334,21 @@ func wideRune(s string) (wide bool, utfsize uint) {
 	return wide, uint(size)
 }
 
+func sanitizeLines(lines []string, width int) []string {
+	// Sanitize lines and truncate them if they're too long.
+	for i, line := range lines {
+		line = Quote(line)
+		if width > 0 {
+			line = Truncate(line, width-2)
+		}
+		if i < len(lines)-1 { // Last line gets no line break.
+			line += "\n"
+		}
+		lines[i] = line
+	}
+	return lines
+}
+
 // SetStatus updates the status lines.
 // The lines should not contain newlines; this method adds them.
 func (t *Terminal) SetStatus(lines []string) {
@@ -352,17 +367,7 @@ func (t *Terminal) SetStatus(lines []string) {
 		}
 	}
 
-	// Sanitize lines and truncate them if they're too long.
-	for i, line := range lines {
-		line = Quote(line)
-		if width > 0 {
-			line = Truncate(line, width-2)
-		}
-		if i < len(lines)-1 { // Last line gets no line break.
-			line += "\n"
-		}
-		lines[i] = line
-	}
+	sanitizeLines(lines, width)
 
 	select {
 	case t.status <- status{lines: lines}:

internal/ui/termstatus/status_test.go

@@ -1,6 +1,7 @@
 package termstatus
 
 import (
+	"reflect"
 	"strconv"
 	"testing"
 
@@ -91,3 +92,26 @@ func BenchmarkTruncateUnicode(b *testing.B) {
 
 	benchmarkTruncate(b, s, w-1)
 }
+
+func TestSanitizeLines(t *testing.T) {
+	var tests = []struct {
+		input  []string
+		width  int
+		output []string
+	}{
+		{[]string{""}, 80, []string{""}},
+		{[]string{"too long test line"}, 10, []string{"too long"}},
+		{[]string{"too long test line", "text"}, 10, []string{"too long\n", "text"}},
+		{[]string{"too long test line", "second long test line"}, 10, []string{"too long\n", "second l"}},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			out := sanitizeLines(test.input, test.width)
+			if !reflect.DeepEqual(out, test.output) {
+				t.Fatalf("wrong output for input %v, width %d: want %q, got %q",
+					test.input, test.width, test.output, out)
+			}
+		})
+	}
+}