Exception during chunked transfer is suppressed

Regression seen with resteasy 3.1.4: An exception thrown during chunked transfer is erroneously suppressed by resteasy. Thus the servlet container deems the call successful and writes a valid end-chunk, the client has no chance to see that there was an error. One common usecase would be to detect whether a large download was completed successfully.

Reproducable by e.g.:

    @Path("ErrorAfterFlushWithoutBody")
    @GET
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    public void errorAfterFlushWithoutBody(@Context HttpServletResponse response) throws IOException {
        response.getOutputStream().flush();
        throw new IOException("a strange io error");
    }

    @Test
    public void testFlushWithoutBody() throws Exception {
        String data = NetworkClient.readIgnoreException("localhost", service.getPort(), "/ErrorAfterFlushWithoutBody");

        Assert.assertTrue(data.startsWith("HTTP/1.1 200 "));
        Assert.assertTrue(data.contains("Transfer-Encoding: chunked"));
        // there must be no end-chunk
        Assert.assertFalse(data.endsWith("0"));
    }

It seems this problem was introduced by this change in SynchronousDispatcher:writeException during RESTEASY-1238 since 3.0.23.Final, 3.1.3.Final .

-      if (response.isCommitted()) throw new UnhandledException(Messages.MESSAGES.responseIsCommitted(), e);
+      if (response.isCommitted())
+      {
+         LogMessages.LOGGER.debug(Messages.MESSAGES.responseIsCommitted());
+         return;
+      }

(... Error handling during chunked transfers is a long sore point. Tomcat was broken until early tomcat8: wrote a valid end-chunk on exception although it should terminate the connection without end-chunk. Apache HttpClient until ~2 years ago was also broken, it simply ignored missing end-chunks due to some broken IIS which always omitted end-chunks. Browsers always ignore missing end-chunks because users have no good options on how to deal with it. The Problem was finally fixed in tomcat+httpclient and i am unhappy to see it resurface with resteasy)