Support custom path escaping for WebSeeds

spec.go

@@ -19,9 +19,11 @@ type TorrentSpec struct {
 	InfoBytes []byte
 	// The name to use if the Name field from the Info isn't available.
 	DisplayName string
-	Webseeds    []string
-	DhtNodes    []string
-	PeerAddrs   []string
+	// WebSeed URLs. For additional options add the URLs separately with Torrent.AddWebSeeds
+	// instead.
+	Webseeds  []string
+	DhtNodes  []string
+	PeerAddrs []string
 	// The combination of the "xs" and "as" fields in magnet links, for now.
 	Sources []string
 

torrent.go

@@ -2350,15 +2350,24 @@ func (t *Torrent) callbacks() *Callbacks {
 	return &t.cl.config.Callbacks
 }
 
-func (t *Torrent) AddWebSeeds(urls []string) {
-	t.cl.lock()
-	defer t.cl.unlock()
-	for _, u := range urls {
-		t.addWebSeed(u)
+type AddWebSeedsOpt func(*webseed.Client)
+
+// Sets the WebSeed trailing path escaper for a webseed.Client.
+func WebSeedPathEscaper(custom webseed.PathEscaper) AddWebSeedsOpt {
+	return func(c *webseed.Client) {
+		c.PathEscaper = custom
 	}
 }
 
-func (t *Torrent) addWebSeed(url string) {
+func (t *Torrent) AddWebSeeds(urls []string, opts ...AddWebSeedsOpt) {
+	t.cl.lock()
+	defer t.cl.unlock()
+	for _, u := range urls {
+		t.addWebSeed(u, opts...)
+	}
+}
+
+func (t *Torrent) addWebSeed(url string, opts ...AddWebSeedsOpt) {
 	if t.cl.config.DisableWebseeds {
 		return
 	}
@@ -2399,6 +2408,9 @@ func (t *Torrent) addWebSeed(url string) {
 		activeRequests: make(map[Request]webseed.Request, maxRequests),
 		maxRequests:    maxRequests,
 	}
+	for _, opt := range opts {
+		opt(&ws.client)
+	}
 	ws.peer.initUpdateRequestsTimer()
 	ws.requesterCond.L = t.cl.locker()
 	for i := 0; i < maxRequests; i += 1 {

webseed/client.go

@@ -52,6 +52,7 @@ type Client struct {
 	// private in the future, if Client ever starts removing pieces.
 	Pieces              roaring.Bitmap
 	ResponseBodyWrapper ResponseBodyWrapper
+	PathEscaper         PathEscaper
 }
 
 type ResponseBodyWrapper func(io.Reader) io.Reader
@@ -76,7 +77,10 @@ func (ws *Client) NewRequest(r RequestSpec) Request {
 	ctx, cancel := context.WithCancel(context.Background())
 	var requestParts []requestPart
 	if !ws.fileIndex.Locate(r, func(i int, e segments.Extent) bool {
-		req, err := NewRequest(ws.Url, i, ws.info, e.Start, e.Length)
+		req, err := newRequest(
+			ws.Url, i, ws.info, e.Start, e.Length,
+			ws.PathEscaper,
+		)
 		if err != nil {
 			panic(err)
 		}

webseed/request.go

@@ -10,30 +10,48 @@ import (
 	"github.com/anacrolix/torrent/metainfo"
 )
 
+type PathEscaper func(pathComps []string) string
+
 // Escapes path name components suitable for appending to a webseed URL. This works for converting
 // S3 object keys to URLs too.
+//
+// Contrary to the name, this actually does a QueryEscape, rather than a PathEscape. This works
+// better with most S3 providers.
 func EscapePath(pathComps []string) string {
-	return path.Join(
-		func() (ret []string) {
-			for _, comp := range pathComps {
-				ret = append(ret, url.QueryEscape(comp))
-			}
-			return
-		}()...,
-	)
+	return defaultPathEscaper(pathComps)
 }
 
-func trailingPath(infoName string, fileComps []string) string {
-	return EscapePath(append([]string{infoName}, fileComps...))
+func defaultPathEscaper(pathComps []string) string {
+	var ret []string
+	for _, comp := range pathComps {
+		ret = append(ret, url.QueryEscape(comp))
+	}
+	return path.Join(ret...)
+}
+
+func trailingPath(
+	infoName string,
+	fileComps []string,
+	pathEscaper PathEscaper,
+) string {
+	if pathEscaper == nil {
+		pathEscaper = defaultPathEscaper
+	}
+	return pathEscaper(append([]string{infoName}, fileComps...))
 }
 
 // Creates a request per BEP 19.
-func NewRequest(url_ string, fileIndex int, info *metainfo.Info, offset, length int64) (*http.Request, error) {
+func newRequest(
+	url_ string, fileIndex int,
+	info *metainfo.Info,
+	offset, length int64,
+	pathEscaper PathEscaper,
+) (*http.Request, error) {
 	fileInfo := info.UpvertedFiles()[fileIndex]
 	if strings.HasSuffix(url_, "/") {
 		// BEP specifies that we append the file path. We need to escape each component of the path
 		// for things like spaces and '#'.
-		url_ += trailingPath(info.Name, fileInfo.Path)
+		url_ += trailingPath(info.Name, fileInfo.Path, pathEscaper)
 	}
 	req, err := http.NewRequest(http.MethodGet, url_, nil)
 	if err != nil {

webseed/request_test.go

@@ -2,28 +2,71 @@ package webseed
 
 import (
 	"net/url"
+	"path"
 	"testing"
 
 	qt "github.com/frankban/quicktest"
 )
 
-func TestTrailingPath(t *testing.T) {
+func TestEscapePath(t *testing.T) {
 	c := qt.New(t)
-	test := func(parts []string, result string) {
-		unescaped, err := url.QueryUnescape(trailingPath(parts[0], parts[1:]))
+	test := func(
+		parts []string, result string,
+		escaper PathEscaper,
+		unescaper func(string) (string, error),
+	) {
+		unescaped, err := unescaper(escaper(parts))
 		if !c.Check(err, qt.IsNil) {
 			return
 		}
 		c.Check(unescaped, qt.Equals, result)
 	}
-	test([]string{"a_b-c", "d + e.f"}, "a_b-c/d + e.f")
-	test([]string{"a_1-b_c2", "d 3. (e, f).g"},
+
+	// Test with nil escapers (always uses url.QueryEscape)
+	// ------
+	test(
+		[]string{"a_b-c", "d + e.f"},
+		"a_b-c/d + e.f",
+		defaultPathEscaper,
+		url.QueryUnescape,
+	)
+	test(
+		[]string{"a_1-b_c2", "d 3. (e, f).g"},
 		"a_1-b_c2/d 3. (e, f).g",
+		defaultPathEscaper,
+		url.QueryUnescape,
+	)
+
+	// Test with custom escapers
+	// ------
+	test(
+		[]string{"a_b-c", "d + e.f"},
+		"a_b-c/d + e.f",
+		func(s []string) string {
+			var ret []string
+			for _, comp := range s {
+				ret = append(ret, url.PathEscape(comp))
+			}
+			return path.Join(ret...)
+		},
+		url.PathUnescape,
+	)
+	test(
+		[]string{"a_1-b_c2", "d 3. (e, f).g"},
+		"a_1-b_c2/d 3. (e, f).g",
+		func(s []string) string {
+			var ret []string
+			for _, comp := range s {
+				ret = append(ret, url.PathEscape(comp))
+			}
+			return path.Join(ret...)
+		},
+		url.PathUnescape,
 	)
 }
 
-func TestTrailingPathForEmptyInfoName(t *testing.T) {
-	qt.Check(t, trailingPath("", []string{`ノ┬─┬ノ ︵ ( \o°o)\`}), qt.Equals, "%E3%83%8E%E2%94%AC%E2%94%80%E2%94%AC%E3%83%8E+%EF%B8%B5+%28+%5Co%C2%B0o%29%5C")
-	qt.Check(t, trailingPath("", []string{"hello", "world"}), qt.Equals, "hello/world")
-	qt.Check(t, trailingPath("war", []string{"and", "peace"}), qt.Equals, "war/and/peace")
+func TestEscapePathForEmptyInfoName(t *testing.T) {
+	qt.Check(t, defaultPathEscaper([]string{`ノ┬─┬ノ ︵ ( \o°o)\`}), qt.Equals, "%E3%83%8E%E2%94%AC%E2%94%80%E2%94%AC%E3%83%8E+%EF%B8%B5+%28+%5Co%C2%B0o%29%5C")
+	qt.Check(t, defaultPathEscaper([]string{"hello", "world"}), qt.Equals, "hello/world")
+	qt.Check(t, defaultPathEscaper([]string{"war", "and", "peace"}), qt.Equals, "war/and/peace")
 }