actix-multipart: Fix multipart boundary reading

If we're not ready to read the first line after the multipart field
(which should be a "\r\n" line) then return NotReady instead of Ready(None)
so that we will get called again to read that line.

Without this I was getting MultipartError::Boundary from read_boundary()
because it got the "\r\n" line instead of the boundary.

actix-multipart/CHANGES.md

@@ -1,5 +1,9 @@
 # Changes
 
+## [0.1.5] - 2019-xx-xx
+
+* Multipart handling now handles NotReady during read of boundary #1189
+
 ## [0.1.4] - 2019-09-12
 
 * Multipart handling now parses requests which do not end in CRLF #1038

actix-multipart/src/server.rs

@@ -604,7 +604,7 @@ impl InnerField {
             }
 
             match payload.readline()? {
-                None => Async::Ready(None),
+                None => Async::NotReady,
                 Some(line) => {
                     if line.as_ref() != b"\r\n" {
                         log::warn!("multipart field did not read all the data or it is malformed");