fix completion UI breaking on window change

Related to #1067.  This commit fixes a problem with the width not being
updated in the completion UI as a side effect of ignoring SIGWINCH.

core/main_loop.py

@@ -11,7 +11,7 @@
 """
 from __future__ import print_function
 
-import sys
+import sys, signal
 
 from _devbuild.gen.syntax_asdl import (
     command_t, command, parse_result__Node, parse_result_e
@@ -203,6 +203,8 @@ def Interactive(flag, cmd_ev, c_parser, display, prompt_plugin, errfmt):
       # - display.EraseLines() needs to be called BEFORE displaying anything, so
       # it appears in all branches.
 
+      signal.signal(signal.SIGWINCH, lambda x, y: display.OnWindowChange())
+
       while True:  # ONLY EXECUTES ONCE
         prompt_plugin.Run()
         try:
@@ -248,6 +250,8 @@ def Interactive(flag, cmd_ev, c_parser, display, prompt_plugin, errfmt):
 
         display.EraseLines()  # Clear candidates right before executing
 
+        signal.signal(signal.SIGWINCH, signal.SIG_IGN)
+
         # to debug the slightly different interactive prasing
         if cmd_ev.exec_opts.noexec():
           ui.PrintAst(node, flag)

core/pyos.py

@@ -280,13 +280,6 @@ def InitInteractiveShell(self, display):
     # This prevents Ctrl-Z from suspending OSH in interactive mode.
     signal.signal(signal.SIGTSTP, signal.SIG_IGN)
 
-    # Register a callback to receive terminal width changes.
-    # NOTE: In line_input.c, we turned off rl_catch_sigwinch.
-    #signal.signal(signal.SIGWINCH, lambda x, y: display.OnWindowChange())
-
-    # Disabled because it causes wait builtin to abort (issue 1067)
-    signal.signal(signal.SIGWINCH, signal.SIG_IGN)
-
   def AddUserTrap(self, sig_num, handler):
     # type: (int, Any) -> None
     """For user-defined handlers registered with the 'trap' builtin."""