fix(server[new_session]): Fix passing both window command and environment (#553)

If the `-e this=that` options are passed after a window command,
tmux (correctly, IMHO) interprets them as options to be passed to
the command itself, does not change the environment, and passes them
through to the command, which does not usually expect to get
a whole lot of `-e this=that -e other=something` options.

Author: ppentchev

src/libtmux/server.py

@@ -499,9 +499,6 @@ def new_session(
         if y is not None:
             tmux_args += ("-y", y)
 
-        if window_command:
-            tmux_args += (window_command,)
-
         if environment:
             if has_gte_version("3.2"):
                 for k, v in environment.items():
@@ -511,6 +508,9 @@ def new_session(
                     "Environment flag ignored, tmux 3.2 or newer required.",
                 )
 
+        if window_command:
+            tmux_args += (window_command,)
+
         proc = self.cmd("new-session", *tmux_args)
 
         if proc.stderr:

tests/test_server.py

@@ -1,7 +1,9 @@
 """Test for libtmux Server object."""
 
 import logging
+import os
 import subprocess
+import time
 
 import pytest
 
@@ -131,6 +133,28 @@ def test_new_session_shell(server: Server) -> None:
         assert pane_start_command == cmd
 
 
+def test_new_session_shell_env(server: Server) -> None:
+    """Verify ``Server.new_session`` creates valid session running w/ command."""
+    cmd = "sleep 1m"
+    env = dict(os.environ)
+    mysession = server.new_session(
+        "test_new_session_env", window_command=cmd, environment=env
+    )
+    time.sleep(0.1)
+    window = mysession.windows[0]
+    pane = window.panes[0]
+    assert mysession.session_name == "test_new_session_env"
+    assert server.has_session("test_new_session_env")
+
+    pane_start_command = pane.pane_start_command
+    assert pane_start_command is not None
+
+    if has_gte_version("3.2"):
+        assert pane_start_command.replace('"', "") == cmd
+    else:
+        assert pane_start_command == cmd
+
+
 @pytest.mark.skipif(has_version("3.2"), reason="Wrong width returned with 3.2")
 def test_new_session_width_height(server: Server) -> None:
     """Verify ``Server.new_session`` creates valid session running w/ dimensions."""