Allow easily injecting env vars from the login shell config into the env in which kitty runs child processes

Fixes #9042

docs/changelog.rst

@@ -137,6 +137,10 @@ Detailed list of changes
 0.43.2 [future]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+- Allow kitty to read a specified set of environment variables from your
+  login shell at startup using the :opt:`env` directive in kitty.conf
+  (:iss:`9042`)
+
 - Fix a regression in 0.43.0 that caused a black flicker when closing a tab in
   the presence of a background image (:iss:`9060`)
 

docs/faq.rst

@@ -480,6 +480,16 @@ related to localization, such as :envvar:`LANG`, ``LC_*`` and loading of
 configuration files such as ``XDG_*``, :envvar:`KITTY_CONFIG_DIRECTORY` and,
 most importantly, ``PATH`` to locate binaries.
 
+The simplest way to fix this is to have kitty load the environment variables
+from your shell configuration at startup using the :opt:`env` directive,
+adding the following to :file:`kitty.conf`::
+
+    env read_from_login_shell=PATH LANG LC_* XDG_* EDITOR VISUAL
+
+This works for POSIX compliant shells and the fish shell. Note that it
+does add significantly to kitty startup time, so use only if really necessary.
+This feature was added in version ``0.43.2``.
+
 To see the environment variables that kitty sees, you can add the following
 mapping to :file:`kitty.conf`::
 

kitty/main.py

@@ -67,6 +67,7 @@ from .utils import (
     get_custom_window_icon,
     log_error,
     parse_os_window_state,
+    read_shell_environment,
     safe_mtime,
     startup_notification_handler,
 )
@@ -478,6 +479,17 @@ def setup_environment(opts: Options, cli_opts: CLIOptions) -> None:
         from_config_file = True
     if cli_opts.listen_on:
         cli_opts.listen_on = expand_listen_on(cli_opts.listen_on, from_config_file)
+    if vars := opts.env.pop('read_from_login_shell', ''):
+        import fnmatch
+        import re
+        senv = read_shell_environment(opts)
+        patterns = tuple(re.compile(fnmatch.translate(x.strip())) for x in vars.split() if x.strip())
+        if patterns:
+            for k, v in senv.items():
+                for pat in patterns:
+                    if pat.match(k) is not None:
+                        opts.env[k] = v
+                        break
     env = opts.env.copy()
     ensure_kitty_in_path()
     ensure_kitten_in_path()

kitty/options/definition.py

@@ -3254,7 +3254,9 @@ Changing this option by reloading the config is not supported.
 '''
     )
 
-opt('+env', '',
+opt(
+    '+env',
+    '',
     option_type='env',
     add_to_default=False,
     long_text='''
@@ -3268,8 +3270,17 @@ recursively, for example::
     env VAR2=${HOME}/${VAR1}/b
 
 The value of :code:`VAR2` will be :code:`<path to home directory>/a/b`.
-'''
-    )
+
+Use the special
+value :code:`read_from_login_shell` to have kitty read the specified variables from
+your :opt:`login shell <shell>` configuration.
+Useful if your shell startup files setup a bunch of environment variables that you want available to kitty and
+in kitty session files. Each variable name is treated as a glob pattern to match. For example:
+:code:`env read_from_login_shell=PATH LANG LC_* XDG_* EDITOR VISUAL`. Note that these variables are only
+read after the configuration is fully processed, thus they are not available for recursive expansion and
+they will override any variables set by other :opt:`env` directives.
+''',
+)
 
 opt('+filter_notification', '', option_type='filter_notification', add_to_default=False, long_text='''
 Specify rules to filter out notifications sent by applications running in kitty.

kitty/utils.py

@@ -748,12 +748,13 @@ def which(name: str, only_system: bool = False) -> str | None:
 def read_resolved_shell_environment(shell: tuple[str, ...]) -> MappingProxyType[str, str]:
     import subprocess
     cmdline = list(shell)
-    if '-l' not in cmdline and '--login' not in shell:
+    if '-l' not in cmdline and '--login' not in cmdline:
         cmdline += ['-l']
-    if '-i' not in shell and '--interactive' not in shell:
+    if '-i' not in cmdline and '--interactive' not in cmdline:
         cmdline += ['-i']
-    is_fish = 'fish' in os.path.basename(cmdline[0]).lower()
-    cmd = 'command env -0' if is_fish else 'builtin command env -0'
+    q = os.path.basename(cmdline[0]).lower()
+    has_builtin = q in ('bash', 'zsh')
+    cmd = 'builtin command env -0' if has_builtin else 'command env -0'
     ans: MappingProxyType[str, str] = MappingProxyType({})
 
     from .child import openpty
@@ -764,7 +765,7 @@ def read_resolved_shell_environment(shell: tuple[str, ...]) -> MappingProxyType[
             cmdline + ['-c', cmd], stdout=slave, stdin=slave, stderr=slave, start_new_session=True, close_fds=True,
             preexec_fn=clear_handled_signals)
     except FileNotFoundError:
-        log_error('Could not find shell to read environment')
+        log_error(f'Could not find shell {cmdline[0]} to read environment')
         return ans
     with os.fdopen(master, 'rb') as stdout, os.fdopen(slave, 'wb'):
         raw = b''
@@ -781,7 +782,7 @@ def read_resolved_shell_environment(shell: tuple[str, ...]) -> MappingProxyType[
             if ret is not None:
                 break
         if ret is None:
-            log_error('Timed out waiting for shell to quit while reading shell environment')
+            log_error(f'Timed out waiting for shell {cmdline} to quit while reading shell environment')
             p.kill()
         elif ret == 0:
             while True:
@@ -800,7 +801,7 @@ def read_resolved_shell_environment(shell: tuple[str, ...]) -> MappingProxyType[
                     env[k] = v
             ans = MappingProxyType(env)
         else:
-            log_error('Failed to run shell to read its environment')
+            log_error(f'Failed to run shell {cmdline} to read its environment')
     return ans