fix: avoids deadlock when requesting info on disconnected inlet

* Adds test to for calling info on a disconnected stream_inlet to
  testing/ext/discovery.cpp
* Fixes deadlock that occurred by checking return value of
  buffer.connect and throwing a system_error based on the error_code in
  buffer if the check fails.

issue: #201

Author: noah-roberts

src/info_receiver.cpp

@@ -52,7 +52,10 @@ void lsl::info_receiver::info_thread() {
 				buffer.register_at(&conn_);
 				std::iostream server_stream(&buffer);
 				// connect...
-				buffer.connect(conn_.get_tcp_endpoint());
+				if (nullptr == buffer.connect(conn_.get_tcp_endpoint()))
+				{
+					throw asio::system_error(buffer.error());
+				}
 				// send the query
 				server_stream << "LSL:fullinfo\r\n" << std::flush;
 				// receive and parse the response

testing/ext/discovery.cpp

@@ -43,5 +43,21 @@ TEST_CASE("fullinfo", "[inlet][fullinfo][basic]") {
 	CHECK(fullinfo.desc().child_value("info") == extinfo);
 }
 
+TEST_CASE("downed outlet deadlock", "[inlet][streaminfo]")
+{
+	// This test verifies that calling info on a resolved inlet that has become disconnected
+	// does not get locked waiting on a response.
+	auto outlet = std::make_unique<lsl::stream_outlet>(lsl::stream_info("deadtest", "type"));
+
+	auto resolved = lsl::resolve_streams();
+	REQUIRE(!resolved.empty());
+	lsl::stream_inlet inlet(resolved[0]);
+
+	outlet.reset();
+
+	// this would previously deadlock
+	CHECK_THROWS(inlet.info());
+}
+
 
 } // namespace