feat(builder): allow environments for windows and panes

CHANGES

@@ -17,7 +17,28 @@ $ pipx install --suffix=@next 'tmuxp' --pip-args '\--pre' --force
 
 ## tmuxp 1.19.x (unreleased)
 
-- Notes on upcoming releases will be added here
+### What's new
+
+- #845: allow to configure window and pane specific environment variables
+
+  Having a setup like:
+  ```yaml
+  session_name: env-demo
+  environment:
+    DATABASE_URL: "sqlite3:///default.db"
+  windows:
+    - window_name: dev
+      environment:
+        DATABASE_URL: "sqlite3:///dev-1.db"
+      panes:
+        - pane
+        - environment:
+            DATABASE_URL: "sqlite3:///dev-2.db"
+  ```
+  will result in a window with two panes. In the first pane `$DATABASE_URL` is
+  `sqlite3:///dev-1.db`, while in the second pane it is `sqlite3://dev-2.db`.
+  Any freshly created window gets `sqlite3:///default.db` as this is what was
+  defined for the session.
 
 <!-- Maintainers, insert changes / features for the next release here -->
 

docs/configuration/examples.md

@@ -262,7 +262,9 @@ please make a ticket on the [issue tracker][issue tracker].
 
 ## Environment variables
 
-tmuxp will set session environment variables.
+tmuxp will set session, window and pane environment variables. Note that
+setting environment variables for windows and panes requires tmuxp 1.19 or
+newer.
 
 ````{tab} YAML
 

examples/session-environment.json

@@ -2,15 +2,32 @@
   "environment": {
     "EDITOR": "/usr/bin/vim",
     "DJANGO_SETTINGS_MODULE": "my_app.settings.local",
-    "SERVER_PORT": "8009",
-  },  
+    "SERVER_PORT": "8009"
+  },
   "windows": [
     {
       "panes": [
-	"./manage.py runserver 0.0.0.0:${SERVER_PORT}"
-      ], 
+        "./manage.py runserver 0.0.0.0:${SERVER_PORT}"
+      ],
       "window_name": "Django project"
-    }, 
-  ], 
+    },
+    {
+      "environment": {
+        "DJANGO_SETTINGS_MODULE": "my_app.settings.local",
+        "SERVER_PORT": "8010"
+      },
+      "panes": [
+        "./manage.py runserver 0.0.0.0:${SERVER_PORT}",
+        {
+          "environment": {
+            "DJANGO_SETTINGS_MODULE": "my_app.settings.local-testing",
+            "SERVER_PORT": "8011"
+          },
+          "shell_command": "./manage.py runserver 0.0.0.0:${SERVER_PORT}"
+        }
+      ],
+      "window_name": "Another Django project"
+    }
+  ],
   "session_name": "Environment variables test"
-}
+}

examples/session-environment.yaml

@@ -7,3 +7,13 @@ windows:
   - window_name: Django project
     panes:
       - ./manage.py runserver 0.0.0.0:${SERVER_PORT}
+  - window_name: Another Django project
+    environment:
+      DJANGO_SETTINGS_MODULE: my_app.settings.local
+      SERVER_PORT: "8010"
+    panes:
+      - ./manage.py runserver 0.0.0.0:${SERVER_PORT}
+      - environment:
+          DJANGO_SETTINGS_MODULE: my_app.settings.local-testing
+          SERVER_PORT: "8011"
+        shell_command: ./manage.py runserver 0.0.0.0:${SERVER_PORT}

src/tmuxp/workspace/builder.py

@@ -7,6 +7,7 @@
 import logging
 import time
 
+from libtmux.common import has_lt_version
 from libtmux.exc import TmuxSessionExists
 from libtmux.pane import Pane
 from libtmux.server import Server
@@ -346,12 +347,31 @@ def iter_create_windows(self, session, append=False):
             except (KeyError, IndexError):
                 pass
 
+            environment = panes[0].get("environment", wconf.get("environment"))
+            if environment and has_lt_version("3.0"):
+                # Falling back to use the environment of the first pane for the window
+                # creation is nice but yields misleading error messages.
+                pane_env = panes[0].get("environment")
+                win_env = wconf.get("environment")
+                if pane_env and win_env:
+                    target = "panes and windows"
+                elif pane_env:
+                    target = "panes"
+                else:
+                    target = "windows"
+                logging.warning(
+                    f"Cannot set environment for new {target}. "
+                    "You need tmux 3.0 or newer for this."
+                )
+                environment = None
+
             w = session.new_window(
                 window_name=window_name,
                 start_directory=sd,
                 attach=False,  # do not move to the new window
                 window_index=wconf.get("window_index", ""),
                 window_shell=ws,
+                environment=environment,
             )
 
             if is_first_window_pass:  # if first window, use window 1
@@ -418,11 +438,24 @@ def get_pane_shell():
                     else:
                         return None
 
+                environment = pconf.get("environment", wconf.get("environment"))
+                if environment and has_lt_version("3.0"):
+                    # Just issue a warning when the environment comes from the pane
+                    # configuration as a warning for the window was already issued when
+                    # the window was created.
+                    if pconf.get("environment"):
+                        logging.warning(
+                            "Cannot set environment for new panes. "
+                            "You need tmux 3.0 or newer for this."
+                        )
+                    environment = None
+
                 p = w.split_window(
                     attach=True,
                     start_directory=get_pane_start_directory(),
                     shell=get_pane_shell(),
                     target=p.id,
+                    environment=environment,
                 )
 
             assert isinstance(p, Pane)

tests/fixtures/workspace/builder/environment_vars.yaml

@@ -1,9 +1,32 @@
 session_name: test env vars
-start_directory: '~'
+start_directory: "~"
 environment:
-  FOO: BAR
+  FOO: SESSION
   PATH: /tmp
 windows:
-- window_name: editor
+- window_name: no_overrides
   panes:
   - pane
+- window_name: window_overrides
+  environment:
+    FOO: WINDOW
+  panes:
+  - pane
+- window_name: pane_overrides
+  panes:
+  - environment:
+      FOO: PANE
+- window_name: both_overrides
+  environment:
+    FOO: WINDOW
+  panes:
+  - pane
+  - environment:
+      FOO: PANE
+# This test case it just needed for warnings issued in old versions of tmux.
+- window_name: both_overrides_on_first_pane
+  environment:
+    FOO: WINDOW
+  panes:
+  - environment:
+      FOO: PANE

tests/workspace/test_builder.py

@@ -9,6 +9,7 @@
 
 import libtmux
 from libtmux.common import has_gte_version, has_lt_version
+from libtmux.session import Session
 from libtmux.test import retry_until, temp_session
 from libtmux.window import Window
 from tmuxp import exc
@@ -331,18 +332,95 @@ def f():
         assert w.name != "top"
 
 
+@pytest.mark.skipif(
+    has_lt_version("3.0"),
+    reason="needs -e flag for new-window and split-window introduced in tmux 3.0",
+)
 def test_environment_variables(session):
     workspace = ConfigReader._from_file(
         test_utils.get_workspace_file("workspace/builder/environment_vars.yaml")
     )
     workspace = loader.expand(workspace)
 
+    builder = WorkspaceBuilder(sconf=workspace)
+    builder.build(session)
+    # Give slow shells some time to settle as otherwise tests might fail.
+    time.sleep(0.3)
+
+    assert session.getenv("FOO") == "SESSION"
+    assert session.getenv("PATH") == "/tmp"
+
+    no_overrides_win = session.windows[0]
+    pane = no_overrides_win.panes[0]
+    pane.send_keys("echo $FOO")
+    assert pane.capture_pane()[1] == "SESSION"
+
+    window_overrides_win = session.windows[1]
+    pane = window_overrides_win.panes[0]
+    pane.send_keys("echo $FOO")
+    assert pane.capture_pane()[1] == "WINDOW"
+
+    pane_overrides_win = session.windows[2]
+    pane = pane_overrides_win.panes[0]
+    pane.send_keys("echo $FOO")
+    assert pane.capture_pane()[1] == "PANE"
+
+    both_overrides_win = session.windows[3]
+    pane = both_overrides_win.panes[0]
+    pane.send_keys("echo $FOO")
+    assert pane.capture_pane()[1] == "WINDOW"
+    pane = both_overrides_win.panes[1]
+    pane.send_keys("echo $FOO")
+    assert pane.capture_pane()[1] == "PANE"
+
+
+@pytest.mark.skipif(
+    has_gte_version("3.0"),
+    reason="warnings are not needed for tmux >= 3.0",
+)
+def test_environment_variables_logs(session: Session, caplog: pytest.LogCaptureFixture):
+    workspace = ConfigReader._from_file(
+        test_utils.get_workspace_file("workspace/builder/environment_vars.yaml")
+    )
+    workspace = loader.expand(workspace)
+
     builder = WorkspaceBuilder(sconf=workspace)
     builder.build(session)
 
-    assert session.getenv("FOO") == "BAR"
+    # environment on sessions should work as this is done using set-environment
+    # on the session itself
+    assert session.getenv("FOO") == "SESSION"
     assert session.getenv("PATH") == "/tmp"
 
+    assert (
+        sum(
+            1
+            for record in caplog.records
+            if "Cannot set environment for new windows." in record.msg
+        )
+        # From window_overrides and both_overrides, but not
+        # both_overrides_in_first_pane.
+        == 2
+    ), "Warning on creating windows missing"
+    assert (
+        sum(
+            1
+            for record in caplog.records
+            if "Cannot set environment for new panes." in record.msg
+        )
+        # From pane_overrides and both_overrides, but not both_overrides_in_first_pane.
+        == 2
+    ), "Warning on creating panes missing"
+    assert (
+        sum(
+            1
+            for record in caplog.records
+            if 'Cannot set environment for new panes and windows.' in record.msg
+        )
+        # From both_overrides_in_first_pane.
+        == 1
+    )
+
 
 def test_automatic_rename_option(session):
     """With option automatic-rename: on."""