feat(strings): Update strings.Indent to error on bad input instead of silently doing nothing (#2089)

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

3 files changed, 56 insertions, 27 deletions

diff --git a/strings/strings.go b/strings/strings.go
index f333b570..248ae9b1 100644
--- a/strings/strings.go
+++ b/strings/strings.go
@@ -15,12 +15,13 @@ import (
 
 // Indent - indent each line of the string with the given indent string.
 // Any indent characters are permitted, except for '\n'.
-//
-// TODO: return an error if the indent string contains '\n' instead of
-// succeeding
-func Indent(width int, indent, s string) string {
-	if width <= 0 || strings.Contains(indent, "\n") {
-		return s
+func Indent(width int, indent, s string) (string, error) {
+	if width <= 0 {
+		return "", fmt.Errorf("width must be > 0")
+	}
+
+	if strings.Contains(indent, "\n") {
+		return "", fmt.Errorf("indent must not contain '\\n'")
 	}
 
 	if width > 1 {
@@ -39,7 +40,8 @@ func Indent(width int, indent, s string) string {
 		res = append(res, c)
 		bol = c == '\n'
 	}
-	return string(res)
+
+	return string(res), nil
 }
 
 // ShellQuote - generate a POSIX shell literal evaluating to a string
diff --git a/strings/strings_fuzz_test.go b/strings/strings_fuzz_test.go
index 4a1fa671..52472c4a 100644
--- a/strings/strings_fuzz_test.go
+++ b/strings/strings_fuzz_test.go
@@ -6,6 +6,7 @@ import (
 	"unicode"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func FuzzIndent(f *testing.F) {
@@ -16,7 +17,19 @@ func FuzzIndent(f *testing.F) {
 	f.Add(15, "\n0", "\n0")
 
 	f.Fuzz(func(t *testing.T, width int, indent, s string) {
-		out := Indent(width, indent, s)
+		out, err := Indent(width, indent, s)
+
+		if width <= 0 {
+			require.Error(t, err)
+			return
+		}
+
+		if strings.Contains(indent, "\n") {
+			require.Error(t, err)
+			return
+		}
+
+		require.NoError(t, err)
 
 		// out should be equal to s when both have the indent character
 		// completely removed.
diff --git a/strings/strings_test.go b/strings/strings_test.go
index 4d16f5ea..0fec6925 100644
--- a/strings/strings_test.go
+++ b/strings/strings_test.go
@@ -9,18 +9,32 @@ import (
 )
 
 func TestIndent(t *testing.T) {
-	actual := "hello\nworld\n!"
+	in := "hello\nworld\n!"
 	expected := "  hello\n  world\n  !"
-	require.Equal(t, actual, Indent(0, "  ", actual))
-	require.Equal(t, actual, Indent(-1, "  ", actual))
-	require.Equal(t, expected, Indent(1, "  ", actual))
-	require.Equal(t, "\n", Indent(1, "  ", "\n"))
-	require.Equal(t, "  foo\n", Indent(1, "  ", "foo\n"))
-	require.Equal(t, "   foo", Indent(1, "   ", "foo"))
-	require.Equal(t, "   foo", Indent(3, " ", "foo"))
-
-	// indenting with newline is not permitted
-	require.Equal(t, "foo", Indent(3, "\n", "foo"))
+
+	actual, err := Indent(1, "  ", in)
+	require.NoError(t, err)
+	require.Equal(t, expected, actual)
+	actual, err = Indent(1, "  ", "\n")
+	require.NoError(t, err)
+	require.Equal(t, "\n", actual)
+	actual, err = Indent(1, "  ", "foo\n")
+	require.NoError(t, err)
+	require.Equal(t, "  foo\n", actual)
+	actual, err = Indent(1, "   ", "foo")
+	require.NoError(t, err)
+	require.Equal(t, "   foo", actual)
+	actual, err = Indent(3, " ", "foo")
+	require.NoError(t, err)
+	require.Equal(t, "   foo", actual)
+
+	// error cases
+	_, err = Indent(3, "\n", "foo")
+	require.Error(t, err)
+	_, err = Indent(-1, "  ", in)
+	require.Error(t, err)
+	_, err = Indent(0, "  ", in)
+	require.Error(t, err)
 }
 
 func BenchmarkIndent(b *testing.B) {
@@ -29,14 +43,14 @@ func BenchmarkIndent(b *testing.B) {
 	outs := make([]string, b.N*8)
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		outs[0+i*8] = Indent(20, " ", longString)
-		outs[1+i*8] = Indent(-1, "  ", actual)
-		outs[2+i*8] = Indent(1, "  ", actual)
-		outs[3+i*8] = Indent(1, "  ", "\n")
-		outs[4+i*8] = Indent(1, "  ", "foo\n")
-		outs[5+i*8] = Indent(1, "   ", "foo")
-		outs[6+i*8] = Indent(3, " ", "foo")
-		outs[7+i*8] = Indent(3, "\n", "foo")
+		outs[0+i*8], _ = Indent(20, " ", longString)
+		outs[1+i*8], _ = Indent(-1, "  ", actual)
+		outs[2+i*8], _ = Indent(1, "  ", actual)
+		outs[3+i*8], _ = Indent(1, "  ", "\n")
+		outs[4+i*8], _ = Indent(1, "  ", "foo\n")
+		outs[5+i*8], _ = Indent(1, "   ", "foo")
+		outs[6+i*8], _ = Indent(3, " ", "foo")
+		outs[7+i*8], _ = Indent(3, "\n", "foo")
 	}
 	b.StopTimer()