Add an env var that can be used to eval an expression at startup of shell

This will come in handy to implement serialization as session
with running of current foreground command.

docs/glossary.rst

@@ -224,6 +224,14 @@ Variables that kitty sets when running child programs
    Set when enabling :ref:`shell_integration`. It is automatically removed by
    the shell integration scripts.
 
+.. envvar:: KITTY_SI_RUN_COMMAND_AT_STARTUP
+
+   Set this to an expression that the kitty shell integration scripts will
+   ``eval`` after the shell is started. Note that this environment variable
+   is ignored when present in the environment in which kitty itself is launched
+   in. It is most useful with the ``--env`` flag for the :doc:`launch <launch>`
+   action.
+
 .. envvar:: ZDOTDIR
 
    Set when enabling :ref:`shell_integration` with :program:`zsh`, allowing

kitty/child.py

@@ -152,6 +152,7 @@ def process_env(env: Mapping[str, str] | None = None) -> dict[str, str]:
         ans.pop(ssl_env_var, None)
     ans.pop('XDG_ACTIVATION_TOKEN', None)
     ans.pop('VTE_VERSION', None)  # Used by the stupid VTE shell integration script that is installed system wide, sigh
+    ans.pop('KITTY_SI_RUN_COMMAND_AT_STARTUP', None)
     return ans
 
 

kitty_tests/shell_integration.py

@@ -86,12 +86,14 @@ class ShellIntegration(BaseTest):
     with_kitten = False
 
     @contextmanager
-    def run_shell(self, shell='zsh', rc='', cmd='', setup_env=None):
+    def run_shell(self, shell='zsh', rc='', cmd='', setup_env=None, extra_env=None):
         home_dir = self.home_dir = os.path.realpath(tempfile.mkdtemp())
         cmd = cmd or shell
         cmd = shlex.split(cmd.format(**locals()))
         env = (setup_env or safe_env_for_running_shell)(cmd, home_dir, rc=rc, shell=shell, with_kitten=self.with_kitten)
         env['KITTY_RUNNING_SHELL_INTEGRATION_TEST'] = '1'
+        if extra_env:
+            env.update(extra_env)
         try:
             if self.with_kitten:
                 cmd = [kitten_exe(), 'run-shell', '--shell', shlex.join(cmd)]
@@ -183,6 +185,10 @@ RPS1="{rps1}"
             self.assert_command(pty)
             env = pty.callbacks.clone_cmds[0].env
             self.ae(env.get('ES'), 'a\n b c\nd')
+        with self.run_shell(rc='PS1=XXX', extra_env={'KITTY_SI_RUN_COMMAND_AT_STARTUP': 'echo pre-start'}) as pty:
+            pty.wait_till(lambda: 'XXX' in pty.screen_contents())
+            self.assertIn('pre-start', pty.screen_contents())
+            self.assertTrue(pty.screen_contents().startswith('pre-start'))
 
     @unittest.skipUnless(shutil.which('fish'), 'fish not installed')
     def test_fish_integration(self):
@@ -190,6 +196,7 @@ RPS1="{rps1}"
         completions_dir = os.path.join(kitty_base_dir, 'shell-integration', 'fish', 'vendor_completions.d')
         with self.run_shell(
             shell='fish',
+            extra_env={'KITTY_SI_RUN_COMMAND_AT_STARTUP': 'echo XXX'},
             rc=f'''
 set -g fish_greeting
 function fish_prompt; echo -n "{fish_prompt}"; end
@@ -198,7 +205,7 @@ function _test_comp_path; contains "{completions_dir}" $fish_complete_path; and
 function _set_key; set -g fish_key_bindings fish_$argv[1]_key_bindings; end
 function _set_status_prompt; function fish_prompt; echo -n "$pipestatus $status {fish_prompt}"; end; end
 ''') as pty:
-            q = fish_prompt + ' ' * (pty.screen.columns - len(fish_prompt) - len(right_prompt)) + right_prompt
+            q = 'XXX\n' + fish_prompt + ' ' * (pty.screen.columns - len(fish_prompt) - len(right_prompt)) + right_prompt
             pty.wait_till(lambda: pty.screen_contents().count(right_prompt) == 1)
             self.ae(pty.screen_contents(), q)
 
@@ -366,6 +373,10 @@ PS1="{ps1}"
                 self.ae(ps1.splitlines()[-1] + 'echo $COLUMNS', str(pty.screen.line(pty.screen.cursor.y - 1 - len(ps1.splitlines()))))
                 self.assert_command(pty, 'echo $COLUMNS')
 
+        with self.run_shell(shell='bash', rc='PS1=XXX', extra_env={'KITTY_SI_RUN_COMMAND_AT_STARTUP': 'echo pre-start'}) as pty:
+            pty.wait_till(lambda: 'XXX' in pty.screen_contents())
+            self.assertIn('pre-start', pty.screen_contents())
+            self.assertTrue(pty.screen_contents().startswith('pre-start'))
         # test startup file sourcing
 
         def setup_env(excluded, argv, home_dir, rc='', shell='bash', with_kitten=self.with_kitten):

shell-integration/bash/kitty.bash

@@ -121,6 +121,8 @@ _ksi_main() {
         fi
         builtin unset SSH_KITTEN_KITTY_DIR
     fi
+    builtin local krcs="$KITTY_SI_RUN_COMMAND_AT_STARTUP"
+    builtin unset KITTY_SI_RUN_COMMAND_AT_STARTUP
 
     _ksi_debug_print() {
         # print a line to STDERR of parent kitty process
@@ -351,6 +353,7 @@ _ksi_main() {
         fi
     fi
     builtin unset KITTY_IS_CLONE_LAUNCH KITTY_CLONE_SOURCE_STRATEGIES
+    if [[ -n "$krcs" ]]; then builtin eval "$krcs"; fi
 }
 _ksi_main
 builtin unset -f _ksi_main

shell-integration/fish/vendor_conf.d/kitty-shell-integration.fish

@@ -37,6 +37,8 @@ function __ksi_schedule --on-event fish_prompt -d "Setup kitty integration after
         end
         set --erase SSH_KITTEN_KITTY_DIR
     end
+    set --local krcs "$KITTY_SI_RUN_COMMAND_AT_STARTUP"
+    set --erase KITTY_SI_RUN_COMMAND_AT_STARTUP
 
     # Enable cursor shape changes for default mode and vi mode
     if not contains "no-cursor" $_ksi
@@ -201,6 +203,9 @@ function __ksi_schedule --on-event fish_prompt -d "Setup kitty integration after
         test (count $new_path) -eq (count $PATH)
         or set --global --export --path PATH $new_path
     end
+    if test -n "$krcs"
+        eval "$krcs"
+    end
 end
 
 function edit-in-kitty --wraps "kitten edit-in-kitty" -d "Edit the specified file in a kitty overlay window with your locally installed editor"

shell-integration/zsh/kitty-integration

@@ -88,6 +88,8 @@ _ksi_deferred_init() {
     builtin local -a opt
     opt=(${(s: :)KITTY_SHELL_INTEGRATION})
     builtin unset KITTY_SHELL_INTEGRATION
+    builtin local krcs="$KITTY_SI_RUN_COMMAND_AT_STARTUP"
+    builtin unset KITTY_SI_RUN_COMMAND_AT_STARTUP
 
     if [[ -n "$SSH_KITTEN_KITTY_DIR" ]]; then
         if [[ ! "$PATH" =~ (^|:)${SSH_KITTEN_KITTY_DIR}(:|$) ]] && [[ -z "$(builtin command -v kitten)" ]]; then
@@ -424,6 +426,9 @@ _ksi_deferred_init() {
     # kitty-integration though because decent public functions aren't supposed to
     # to unfunction themselves when invoked. Unfunctioning is done by calling code.
     builtin unfunction _ksi_deferred_init
+
+    # run startup command
+    if [[ -n "$krcs" ]]; then builtin eval "$krcs"; fi
 }
 
 _ksi_transmit_data() {