serve webdav: make Content-Type without reading the file and add --etag-hash

Before this change x/net/webdav would open each file to find out its
Content-Type.

Now we override the FileInfo and provide that directly from rclone.

An --etag-hash has also been implemented to override the ETag with the
hash passed in.

Fixes #2273

cmd/serve/webdav/webdav.go

@@ -1,8 +1,5 @@
 package webdav
 
-// FIXME need to fix directory listings reading each file - make an
-// override for getcontenttype property?
-
 import (
 	"net/http"
 	"os"
@@ -11,6 +8,7 @@ import (
 	"github.com/ncw/rclone/cmd/serve/httplib"
 	"github.com/ncw/rclone/cmd/serve/httplib/httpflags"
 	"github.com/ncw/rclone/fs"
+	"github.com/ncw/rclone/fs/hash"
 	"github.com/ncw/rclone/fs/log"
 	"github.com/ncw/rclone/vfs"
 	"github.com/ncw/rclone/vfs/vfsflags"
@@ -20,9 +18,15 @@ import (
 	"golang.org/x/net/webdav"
 )
 
+var (
+	hashName string
+	hashType = hash.None
+)
+
 func init() {
 	httpflags.AddFlags(Command.Flags())
 	vfsflags.AddFlags(Command.Flags())
+	Command.Flags().StringVar(&hashName, "etag-hash", "", "Which hash to use for the ETag, or auto or blank for off")
 }
 
 // Command definition for cobra
@@ -35,17 +39,41 @@ remote over HTTP via the webdav protocol. This can be viewed with a
 webdav client or you can make a remote of type webdav to read and
 write it.
 
-NB at the moment each directory listing reads the start of each file
+### Webdav options
-which is undesirable: see https://github.com/golang/go/issues/22577
+
+#### --etag-hash 
+
+This controls the ETag header.  Without this flag the ETag will be
+based on the ModTime and Size of the object.
+
+If this flag is set to "auto" then rclone will choose the first
+supported hash on the backend or you can use a named hash such as
+"MD5" or "SHA-1".
+
+Use "rclone hashsum" to see the full list.
+
 ` + httplib.Help + vfs.Help,
-	Run: func(command *cobra.Command, args []string) {
+	RunE: func(command *cobra.Command, args []string) error {
 		cmd.CheckArgs(1, 1, command, args)
 		f := cmd.NewFsSrc(args)
+		hashType = hash.None
+		if hashName == "auto" {
+			hashType = f.Hashes().GetOne()
+		} else if hashName != "" {
+			err := hashType.Set(hashName)
+			if err != nil {
+				return err
+			}
+		}
+		if hashType != hash.None {
+			fs.Debugf(f, "Using hash %v for ETag", hashType)
+		}
 		cmd.Run(false, false, command, func() error {
 			w := newWebDAV(f, &httpflags.Opt)
 			w.serve()
 			return nil
 		})
+		return nil
 	},
 }
 
@@ -116,7 +144,11 @@ func (w *WebDAV) Mkdir(ctx context.Context, name string, perm os.FileMode) (err
 // OpenFile opens a file or a directory
 func (w *WebDAV) OpenFile(ctx context.Context, name string, flags int, perm os.FileMode) (file webdav.File, err error) {
 	defer log.Trace(name, "flags=%v, perm=%v", flags, perm)("err = %v", &err)
-	return w.vfs.OpenFile(name, flags, perm)
+	f, err := w.vfs.OpenFile(name, flags, perm)
+	if err != nil {
+		return nil, err
+	}
+	return Handle{f}, nil
 }
 
 // RemoveAll removes a file or a directory and its contents
@@ -142,8 +174,84 @@ func (w *WebDAV) Rename(ctx context.Context, oldName, newName string) (err error
 // Stat returns info about the file or directory
 func (w *WebDAV) Stat(ctx context.Context, name string) (fi os.FileInfo, err error) {
 	defer log.Trace(name, "")("fi=%+v, err = %v", &fi, &err)
-	return w.vfs.Stat(name)
+	fi, err = w.vfs.Stat(name)
+	if err != nil {
+		return nil, err
+	}
+	return FileInfo{fi}, nil
 }
 
-// check interface
+// Handle represents an open file
-var _ os.FileInfo = vfs.Node(nil)
+type Handle struct {
+	vfs.Handle
+}
+
+// Readdir reads directory entries from the handle
+func (h Handle) Readdir(count int) (fis []os.FileInfo, err error) {
+	fis, err = h.Handle.Readdir(count)
+	if err != nil {
+		return nil, err
+	}
+	// Wrap each FileInfo
+	for i := range fis {
+		fis[i] = FileInfo{fis[i]}
+	}
+	return fis, nil
+}
+
+// Stat the handle
+func (h Handle) Stat() (fi os.FileInfo, err error) {
+	fi, err = h.Handle.Stat()
+	if err != nil {
+		return nil, err
+	}
+	return FileInfo{fi}, nil
+}
+
+// FileInfo represents info about a file satisfying os.FileInfo and
+// also some additional interfaces for webdav for ETag and ContentType
+type FileInfo struct {
+	os.FileInfo
+}
+
+// ETag returns an ETag for the FileInfo
+func (fi FileInfo) ETag(ctx context.Context) (etag string, err error) {
+	defer log.Trace(fi, "")("etag=%q, err=%v", &etag, &err)
+	if hashType == hash.None {
+		return "", webdav.ErrNotImplemented
+	}
+	node, ok := (fi.FileInfo).(vfs.Node)
+	if !ok {
+		fs.Errorf(fi, "Expecting vfs.Node, got %T", fi.FileInfo)
+		return "", webdav.ErrNotImplemented
+	}
+	entry := node.DirEntry()
+	o, ok := entry.(fs.Object)
+	if !ok {
+		return "", webdav.ErrNotImplemented
+	}
+	hash, err := o.Hash(hashType)
+	if err != nil || hash == "" {
+		return "", webdav.ErrNotImplemented
+	}
+	return `"` + hash + `"`, nil
+}
+
+// ContentType returns a content type for the FileInfo
+func (fi FileInfo) ContentType(ctx context.Context) (contentType string, err error) {
+	defer log.Trace(fi, "")("etag=%q, err=%v", &contentType, &err)
+	node, ok := (fi.FileInfo).(vfs.Node)
+	if !ok {
+		fs.Errorf(fi, "Expecting vfs.Node, got %T", fi.FileInfo)
+		return "application/octet-stream", nil
+	}
+	entry := node.DirEntry()
+	switch x := entry.(type) {
+	case fs.Object:
+		return fs.MimeType(x), nil
+	case fs.Directory:
+		return "inode/directory", nil
+	}
+	fs.Errorf(fi, "Expecting fs.Object or fs.Directory, got %T", entry)
+	return "application/octet-stream", nil
+}

cmd/serve/webdav/webdav_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/ncw/rclone/cmd/serve/httplib"
 	"github.com/ncw/rclone/fstest"
 	"github.com/stretchr/testify/assert"
+	"golang.org/x/net/webdav"
 )
 
 const (
@@ -23,6 +24,13 @@ const (
 	testURL         = "http://" + testBindAddress + "/"
 )
 
+// check interfaces
+var (
+	_ os.FileInfo         = FileInfo{nil}
+	_ webdav.ETager       = FileInfo{nil}
+	_ webdav.ContentTyper = FileInfo{nil}
+)
+
 // TestWebDav runs the webdav server then runs the unit tests for the
 // webdav remote against it.
 func TestWebDav(t *testing.T) {