internal: fixed ETag UnmarshalText problem

For some caldav providers, it wasn't possible to unmarshal unquoted text for etag

internal: test for ETag UnmarshalText

internal/elements.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -377,10 +378,19 @@ type GetETag struct {
 type ETag string
 
 func (etag *ETag) UnmarshalText(b []byte) error {
-	s, err := strconv.Unquote(string(b))
+	s := string(b)
+	shouldUnquote, err := regexp.MatchString("^(['\"\\x60])", s)
 	if err != nil {
-		return fmt.Errorf("webdav: failed to unquote ETag: %v", err)
+		return fmt.Errorf("webdav: unquote check failed: %v", err)
 	}
+
+	if shouldUnquote {
+		s, err = strconv.Unquote(s)
+		if err != nil {
+			return fmt.Errorf("webdav: failed to unquote ETag: %v", err)
+		}
+	}
+
 	*etag = ETag(s)
 	return nil
 }

internal/elements_test.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"bytes"
+	"encoding/binary"
 	"encoding/xml"
 	"strings"
 	"testing"
@@ -63,3 +64,69 @@ func TestTimeRoundTrip(t *testing.T) {
 		t.Fatalf("invalid round-trip:\ngot= %s\nwant=%s", got, want)
 	}
 }
+
+func TestETag_UnmarshalText(t *testing.T) {
+	type args struct {
+		b []byte
+	}
+	tests := []struct {
+		name    string
+		etag    ETag
+		args    args
+		wantErr bool
+	}{
+		{
+			name: "should unmarshal unquoted string",
+			etag: "",
+			args: args{
+				b: []byte("hello world"),
+			},
+			wantErr: false,
+		},
+		{
+			name: "should unmarshal double quoted string",
+			etag: "",
+			args: args{
+				b: []byte("\"hello world\""),
+			},
+			wantErr: false,
+		},
+		{
+			name: "shouldn't unmarshal single quoted string",
+			etag: "",
+			args: args{
+				b: []byte("'hello world'"),
+			},
+			wantErr: true,
+		},
+		{
+			name: "should unmarshal backward quoted string",
+			etag: "",
+			args: args{
+				b: []byte("`hello world`"),
+			},
+			wantErr: false,
+		},
+		{
+			name: "should unmarshal int",
+			etag: "",
+			args: args{
+				b: func() []byte {
+					buf := new(bytes.Buffer)
+					num := 162392347123
+					binary.Write(buf, binary.LittleEndian, num)
+					return buf.Bytes()
+				}(),
+			},
+			wantErr: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := tt.etag.UnmarshalText(tt.args.b); (err != nil) != tt.wantErr {
+				t.Errorf("UnmarshalText() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}