feat(Window.split_window): set up environment

This allows to set up a custom environment when creating a new pane.

Author: zappolowski

src/libtmux/window.py

@@ -9,7 +9,7 @@
 import shlex
 import typing as t
 
-from libtmux.common import tmux_cmd
+from libtmux.common import has_gte_version, tmux_cmd
 from libtmux.pane import Pane
 
 from . import exc, formats
@@ -442,6 +442,7 @@ def split_window(
         vertical: bool = True,
         shell: t.Optional[str] = None,
         percent: t.Optional[int] = None,
+        environment: t.Optional[t.Dict[str, str]] = None,
     ) -> Pane:
         """
         Split window and return the created :class:`Pane`.
@@ -520,6 +521,15 @@ def split_window(
         if not attach:
             tmux_args += ("-d",)
 
+        if environment:
+            if has_gte_version("3.0"):
+                for k, v in environment.items():
+                    tmux_args += (f"-e{k}={v}",)
+            else:
+                logger.warning(
+                    "Cannot set up environment as tmux 3.0 or newer is required."
+                )
+
         if shell:
             tmux_args += (shell,)
 

tests/test_window.py

@@ -1,5 +1,7 @@
 """Test for libtmux Window object."""
 import logging
+import shutil
+import time
 import typing as t
 
 import pytest
@@ -310,3 +312,45 @@ def test_empty_window_name(session: Session) -> None:
         "#{==:#{session_name}," + session.name + "}",
     )
     assert "''" in cmd.stdout
+
+
+@pytest.mark.skipif(
+    has_lt_version("3.0"),
+    reason="needs -e flag for split-window which was introduced in 3.0",
+)
+def test_split_window_with_environment(session: Session) -> None:
+    env = shutil.which("env")
+    assert env is not None, "Cannot find usable `env` in Path."
+
+    window = session.new_window(window_name="split_window_with_environment")
+    pane = window.split_window(
+        shell=f"{env} PS1='$ ' sh",
+        environment={"ENV_VAR": "pane"},
+    )
+    assert pane is not None
+    # wait a bit for the prompt to be ready as the test gets flaky otherwise
+    time.sleep(0.05)
+    pane.send_keys("echo $ENV_VAR")
+    assert pane.capture_pane() == ["$ echo $ENV_VAR", "pane", "$"]
+
+
+@pytest.mark.skipif(
+    has_gte_version("3.0"),
+    reason="3.0 has the -e flag on split-window",
+)
+def test_split_window_with_environment_logs_warning_for_old_tmux(
+    session: Session,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    env = shutil.which("env")
+    assert env is not None, "Cannot find usable `env` in Path."
+
+    window = session.new_window(window_name="split_window_with_environment")
+    window.split_window(
+        shell=f"{env} PS1='$ ' sh",
+        environment={"ENV_VAR": "pane"},
+    )
+
+    assert any(
+        "Cannot set up environment" in record.msg for record in caplog.records
+    ), "Warning missing"