Use a new controlling terminal when reading shell environment

This is because some people do things in their rc files based
on checking the name of the controlling terminal.

kitty/child.py

@@ -118,6 +118,10 @@ def remove_cloexec(fd):
     fcntl.fcntl(fd, fcntl.F_SETFD, fcntl.fcntl(fd, fcntl.F_GETFD) & ~fcntl.FD_CLOEXEC)
 
 
+def remove_blocking(fd):
+    os.set_blocking(fd, False)
+
+
 def default_env():
     try:
         return default_env.env
@@ -132,6 +136,13 @@ def set_default_env(val=None):
     default_env.env = env
 
 
+def openpty():
+    master, slave = os.openpty()  # Note that master and slave are in blocking mode
+    remove_cloexec(slave)
+    fast_data_types.set_iutf8_fd(master, True)
+    return master, slave
+
+
 class Child:
 
     child_fd = pid = None
@@ -178,9 +189,7 @@ def fork(self):
         if self.forked:
             return
         self.forked = True
-        master, slave = os.openpty()  # Note that master and slave are in blocking mode
-        remove_cloexec(slave)
-        fast_data_types.set_iutf8_fd(master, True)
+        master, slave = openpty()
         stdin, self.stdin = self.stdin, None
         ready_read_fd, ready_write_fd = os.pipe()
         remove_cloexec(ready_read_fd)
@@ -206,7 +215,7 @@ def fork(self):
             fast_data_types.thread_write(stdin_write_fd, stdin)
         os.close(ready_read_fd)
         self.terminal_ready_fd = ready_write_fd
-        fcntl.fcntl(self.child_fd, fcntl.F_SETFL, fcntl.fcntl(self.child_fd, fcntl.F_GETFL) | os.O_NONBLOCK)
+        remove_blocking(self.child_fd)
         return pid
 
     def mark_terminal_ready(self):

kitty/main.py

@@ -10,7 +10,7 @@
 
 from .borders import load_borders_program
 from .boss import Boss
-from .child import set_default_env
+from .child import set_default_env, openpty, remove_blocking
 from .cli import create_opts, parse_args
 from .config import cached_values_for, initial_window_size_func
 from .constants import (
@@ -203,23 +203,37 @@ def macos_cmdline(argv_args):
     return ans
 
 
-def read_shell_environment(opts):
+def read_shell_environment(opts=None):
     if not hasattr(read_shell_environment, 'ans'):
         import subprocess
         from .session import resolved_shell
         shell = resolved_shell(opts)
-        p = subprocess.Popen(shell + ['-l', '-c', 'env'], stdout=subprocess.PIPE)
-        raw = p.stdout.read()
-        if p.wait() == 0:
-            raw = raw.decode('utf-8', 'replace')
-            ans = read_shell_environment.ans = {}
-            for line in raw.splitlines():
-                k, v = line.partition('=')[::2]
-                if k and v:
-                    ans[k] = v
-        else:
-            log_error('Failed to run shell to read its environment')
-            read_shell_environment.ans = {}
+        master, slave = openpty()
+        remove_blocking(master)
+        p = subprocess.Popen(shell + ['-l', '-c', 'env'], stdout=slave, stdin=slave, stderr=slave, start_new_session=True, close_fds=True)
+        with os.fdopen(master, 'rb') as stdout, os.fdopen(slave, 'wb'):
+            raw = b''
+            while p.wait(0.01) is None:
+                with suppress(Exception):
+                    raw += stdout.read()
+            if p.returncode == 0:
+                while True:
+                    try:
+                        x = stdout.read()
+                    except Exception:
+                        break
+                    if not x:
+                        break
+                    raw += x
+                raw = raw.decode('utf-8', 'replace')
+                ans = read_shell_environment.ans = {}
+                for line in raw.splitlines():
+                    k, v = line.partition('=')[::2]
+                    if k and v:
+                        ans[k] = v
+            else:
+                log_error('Failed to run shell to read its environment')
+                read_shell_environment.ans = {}
     return read_shell_environment.ans
 
 

kitty/session.py

@@ -74,8 +74,8 @@ def set_cwd(self, val):
         self.tabs[-1].cwd = val
 
 
-def resolved_shell(opts):
-    ans = opts.shell
+def resolved_shell(opts=None):
+    ans = getattr(opts, 'shell', '.')
     if ans == '.':
         ans = [shell_path]
     else: