multipart: fix handling of common prefixes

multifilereader_test.go

@@ -163,3 +163,43 @@ func TestOutput(t *testing.T) {
 		t.Fatal("Expected to get (nil, io.EOF)")
 	}
 }
+
+func TestCommonPrefix(t *testing.T) {
+	sf := NewMapDirectory(map[string]Node{
+		"boop": NewMapDirectory(map[string]Node{
+			"a":   NewBytesFile([]byte("bleep")),
+			"aa":  NewBytesFile([]byte("bleep")),
+			"aaa": NewBytesFile([]byte("bleep")),
+		}),
+	})
+	mfr := NewMultiFileReader(sf, true)
+	reader, err := NewFileFromPartReader(multipart.NewReader(mfr, mfr.Boundary()), multipartFormdataType)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	CheckDir(t, reader, []Event{
+		{
+			kind: TDirStart,
+			name: "boop",
+		},
+		{
+			kind:  TFile,
+			name:  "a",
+			value: "bleep",
+		},
+		{
+			kind:  TFile,
+			name:  "aa",
+			value: "bleep",
+		},
+		{
+			kind:  TFile,
+			name:  "aaa",
+			value: "bleep",
+		},
+		{
+			kind: TDirEnd,
+		},
+	})
+}

multipartfile.go

@@ -111,6 +111,7 @@ func (w *multipartWalker) nextFile() (Node, error) {
 	}, nil
 }
 
+// fileName returns a normalized filename from a part.
 func fileName(part *multipart.Part) string {
 	filename := part.FileName()
 	if escaped, err := url.QueryUnescape(filename); err == nil {
@@ -120,10 +121,32 @@ func fileName(part *multipart.Part) string {
 	return path.Clean("/" + filename)
 }
 
+// dirName appends a slash to the end of the filename, if not present.
+// expects a _cleaned_ path.
+func dirName(filename string) string {
+	if !strings.HasSuffix(filename, "/") {
+		filename += "/"
+	}
+	return filename
+}
+
+// isDirectory checks if the media type is a valid directory media type.
 func isDirectory(mediatype string) bool {
 	return mediatype == multipartFormdataType || mediatype == applicationDirectory
 }
 
+// isChild checks if child is a child of parent directory.
+// expects a _cleaned_ path.
+func isChild(child, parent string) bool {
+	return strings.HasPrefix(child, dirName(parent))
+}
+
+// makeRelative makes the child path relative to the parent path.
+// expects a _cleaned_ path.
+func makeRelative(child, parent string) string {
+	return strings.TrimPrefix(child, dirName(parent))
+}
+
 type multipartIterator struct {
 	f *multipartDirectory
 
@@ -154,18 +177,18 @@ func (it *multipartIterator) Next() bool {
 		name := fileName(part)
 
 		// Is the file in a different directory?
-		if !strings.HasPrefix(name, it.f.path) {
+		if !isChild(name, it.f.path) {
 			return false
 		}
 
 		// Have we already entered this directory?
-		if it.curName != "" && strings.HasPrefix(name, path.Join(it.f.path, it.curName)) {
+		if it.curName != "" && isChild(name, path.Join(it.f.path, it.curName)) {
 			it.f.walker.consumePart()
 			continue
 		}
 
 		// Make the path relative to the current directory.
-		name = strings.TrimLeft(name[len(it.f.path):], "/")
+		name = makeRelative(name, it.f.path)
 
 		// Check if we need to create a fake directory (more than one
 		// path component).