http: improved recognition of url pointing to a single file - fixes #5929

backend/http/http.go

@@ -73,8 +73,9 @@ directories.`,
 			Advanced: true,
 		}, {
 			Name: "no_head",
-			Help: `Don't use HEAD requests to find file sizes in dir listing.
+			Help: `Don't use HEAD requests.
 
+HEAD requests are mainly used to find file sizes in dir listing.
 If your site is being very slow to load then you can try this option.
 Normally rclone does a HEAD request for each potential file in a
 directory listing to:
@@ -134,6 +135,82 @@ func statusError(res *http.Response, err error) error {
 	return nil
 }
 
+// getFsEndpoint decides if url is to be considered a file or directory,
+// and returns a proper endpoint url to use for the fs.
+func getFsEndpoint(ctx context.Context, client *http.Client, url string, opt *Options) (string, bool) {
+	// If url ends with '/' it is already a proper url always assumed to be a directory.
+	if url[len(url)-1] == '/' {
+		return url, false
+	}
+
+	// If url does not end with '/' we send a HEAD request to decide
+	// if it is directory or file, and if directory appends the missing
+	// '/', or if file returns the directory url to parent instead.
+	createFileResult := func() (string, bool) {
+		fs.Debugf(nil, "If path is a directory you must add a trailing '/'")
+		parent, _ := path.Split(url)
+		return parent, true
+	}
+	createDirResult := func() (string, bool) {
+		fs.Debugf(nil, "To avoid the initial HEAD request add a trailing '/' to the path")
+		return url + "/", false
+	}
+
+	// If HEAD requests are not allowed we just have to assume it is a file.
+	if opt.NoHead {
+		fs.Debugf(nil, "Assuming path is a file as --http-no-head is set")
+		return createFileResult()
+	}
+
+	// Use a client which doesn't follow redirects so the server
+	// doesn't redirect http://host/dir to http://host/dir/
+	noRedir := *client
+	noRedir.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}
+	req, err := http.NewRequestWithContext(ctx, "HEAD", url, nil)
+	if err != nil {
+		fs.Debugf(nil, "Assuming path is a file as HEAD request could not be created: %v", err)
+		return createFileResult()
+	}
+	addHeaders(req, opt)
+	res, err := noRedir.Do(req)
+
+	if err != nil {
+		fs.Debugf(nil, "Assuming path is a file as HEAD request could not be sent: %v", err)
+		return createFileResult()
+	}
+	if res.StatusCode == http.StatusNotFound {
+		fs.Debugf(nil, "Assuming path is a directory as HEAD response is it does not exist as a file (%s)", res.Status)
+		return createDirResult()
+	}
+	if res.StatusCode == http.StatusMovedPermanently ||
+		res.StatusCode == http.StatusFound ||
+		res.StatusCode == http.StatusSeeOther ||
+		res.StatusCode == http.StatusTemporaryRedirect ||
+		res.StatusCode == http.StatusPermanentRedirect {
+		redir := res.Header.Get("Location")
+		if redir != "" {
+			if redir[len(redir)-1] == '/' {
+				fs.Debugf(nil, "Assuming path is a directory as HEAD response is redirect (%s) to a path that ends with '/': %s", res.Status, redir)
+				return createDirResult()
+			}
+			fs.Debugf(nil, "Assuming path is a file as HEAD response is redirect (%s) to a path that does not end with '/': %s", res.Status, redir)
+			return createFileResult()
+		}
+		fs.Debugf(nil, "Assuming path is a file as HEAD response is redirect (%s) but no location header", res.Status)
+		return createFileResult()
+	}
+	if res.StatusCode < 200 || res.StatusCode > 299 {
+		// Example is 403 (http.StatusForbidden) for servers not allowing HEAD requests.
+		fs.Debugf(nil, "Assuming path is a file as HEAD response is an error (%s)", res.Status)
+		return createFileResult()
+	}
+
+	fs.Debugf(nil, "Assuming path is a file as HEAD response is success (%s)", res.Status)
+	return createFileResult()
+}
+
 // NewFs creates a new Fs object from the name and root. It connects to
 // the host specified in the config file.
 func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, error) {
@@ -164,37 +241,9 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 
 	client := fshttp.NewClient(ctx)
 
-	var isFile = false
-	if !strings.HasSuffix(u.String(), "/") {
-		// Make a client which doesn't follow redirects so the server
-		// doesn't redirect http://host/dir to http://host/dir/
-		noRedir := *client
-		noRedir.CheckRedirect = func(req *http.Request, via []*http.Request) error {
-			return http.ErrUseLastResponse
-		}
-		// check to see if points to a file
-		req, err := http.NewRequestWithContext(ctx, "HEAD", u.String(), nil)
-		if err == nil {
-			addHeaders(req, opt)
-			res, err := noRedir.Do(req)
-			err = statusError(res, err)
-			if err == nil {
-				isFile = true
-			}
-		}
-	}
-
-	newRoot := u.String()
-	if isFile {
-		// Point to the parent if this is a file
-		newRoot, _ = path.Split(u.String())
-	} else {
-		if !strings.HasSuffix(newRoot, "/") {
-			newRoot += "/"
-		}
-	}
-
-	u, err = url.Parse(newRoot)
+	endpoint, isFile := getFsEndpoint(ctx, client, u.String(), opt)
+	fs.Debugf(nil, "Root: %s", endpoint)
+	u, err = url.Parse(endpoint)
 	if err != nil {
 		return nil, err
 	}
@@ -212,12 +261,16 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 	f.features = (&fs.Features{
 		CanHaveEmptyDirectories: true,
 	}).Fill(ctx, f)
+
 	if isFile {
+		// return an error with an fs which points to the parent
 		return f, fs.ErrorIsFile
 	}
+
 	if !strings.HasSuffix(f.endpointURL, "/") {
 		return nil, errors.New("internal error: url doesn't end with /")
 	}
+
 	return f, nil
 }