markup/goldmark: Change link and image render hook enablement to enums

Closes #13535

helpers/general.go

@@ -255,6 +255,27 @@ func SliceToLower(s []string) []string {
 	return l
 }
 
+// StringSliceToList formats a string slice into a human-readable list.
+// It joins the elements of the slice s with commas, using an Oxford comma,
+// and precedes the final element with the conjunction c.
+func StringSliceToList(s []string, c string) string {
+	const defaultConjunction = "and"
+
+	if c == "" {
+		c = defaultConjunction
+	}
+	if len(s) == 0 {
+		return ""
+	}
+	if len(s) == 1 {
+		return s[0]
+	}
+	if len(s) == 2 {
+		return fmt.Sprintf("%s %s %s", s[0], c, s[1])
+	}
+	return fmt.Sprintf("%s, %s %s", strings.Join(s[:len(s)-1], ", "), c, s[len(s)-1])
+}
+
 // IsWhitespace determines if the given rune is whitespace.
 func IsWhitespace(r rune) bool {
 	return r == ' ' || r == '\t' || r == '\n' || r == '\r'

helpers/general_test.go

@@ -18,9 +18,8 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/gohugoio/hugo/helpers"
-
 	qt "github.com/frankban/quicktest"
+	"github.com/gohugoio/hugo/helpers"
 )
 
 func TestResolveMarkup(t *testing.T) {
@@ -304,3 +303,26 @@ func BenchmarkUniqueStrings(b *testing.B) {
 		}
 	})
 }
+
+func TestStringSliceToList(t *testing.T) {
+	for _, tt := range []struct {
+		slice       []string
+		conjunction string
+		want        string
+	}{
+		{[]string{}, "", ""},
+		{[]string{"foo"}, "", "foo"},
+		{[]string{"foo"}, "and", "foo"},
+		{[]string{"foo", "bar"}, "", "foo and bar"},
+		{[]string{"foo", "bar"}, "and", "foo and bar"},
+		{[]string{"foo", "bar"}, "or", "foo or bar"},
+		{[]string{"foo", "bar", "baz"}, "", "foo, bar, and baz"},
+		{[]string{"foo", "bar", "baz"}, "and", "foo, bar, and baz"},
+		{[]string{"foo", "bar", "baz"}, "or", "foo, bar, or baz"},
+	} {
+		got := helpers.StringSliceToList(tt.slice, tt.conjunction)
+		if got != tt.want {
+			t.Errorf("StringSliceToList() got: %q, want: %q", got, tt.want)
+		}
+	}
+}