Jsonrpc: defend against very large stderr lines

In https://github.com/joaotavora/rassumfrassum/issues/1 we found
a language server that emits very large single-line messages
(5MB): that eventually end up in Eglot's stderr.  With the
output arriving in chunks into the stderr buffer, this creates a
significant slowdown of '[stderr] nil' lines, which eventually
clogs up the stdout JSONRPC communication.

This fix exits the `jsonrpc--forwarding-buffer` function early
if the forward-line call didn't actually move to a new line.

* lisp/jsonrpc.el (jsonrpc--forwarding-buffer): Fix.
(Version): Bump to 1.0.27.

1 files changed, 2 insertions, 2 deletions

diff --git a/lisp/jsonrpc.el b/lisp/jsonrpc.el
index 808c1fdd147..ca2647971fd 100644
--- a/lisp/jsonrpc.el
+++ b/lisp/jsonrpc.el
@@ -4,7 +4,7 @@
 
 ;; Author: João Távora <joaotavora@gmail.com>
 ;; Keywords: processes, languages, extensions
-;; Version: 1.0.26
+;; Version: 1.0.27
 ;; Package-Requires: ((emacs "25.2"))
 
 ;; This is a GNU ELPA :core package.  Avoid functionality that is not
@@ -1109,7 +1109,7 @@ PREFIX to CONN's events buffer."
            (unless (eql max 0)
              (cl-loop initially (goto-char beg)
                       do (forward-line)
-                      when (bolp)
+                      while (bolp)
                       for line = (buffer-substring
                                   (line-beginning-position 0)
                                   (line-end-position 0))