From 0edaf42d100053ed35051c0281f039572007d16a Mon Sep 17 00:00:00 2001
From: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Mon, 21 Jan 2019 20:29:31 -0600
Subject: [PATCH] Fix regression for #4178 and others introduced by 364c839

...while still keeping intact the fix for #5519.
---
 src/reader.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/reader.cpp b/src/reader.cpp
index 78e930f63..b2c241952 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -2492,8 +2492,16 @@ const wchar_t *reader_readline(int nchars) {
     if (tcgetattr(STDIN_FILENO, &old_modes) == -1 && errno == EIO) redirect_tty_output();
     // Set the new modes.
     if (tcsetattr(0, TCSANOW, &shell_modes) == -1) {
-        if (errno == EIO) redirect_tty_output();
-        wperror(L"tcsetattr");
+        int err = errno;
+        if (err == EIO) {
+            redirect_tty_output();
+        }
+        // This check is required to work around certain issues with fish's approach to
+        // terminal control when launching interactive processes while in non-interactive
+        // mode. See #4178 for one such example.
+        if (err != ENOTTY || is_interactive_session) {
+            wperror(L"tcsetattr");
+        }
     }
 
     while (!finished && !data->end_loop) {