Allow deleting environment vars from the child environment using env

docs/changelog.rst

@@ -40,6 +40,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - hints kitten: Fix a regression that caused using the default open program
   to trigger open actions instead of running the program (:iss:`3968`)
 
+- Allow deleting environment variables in :opt:`env` by specifying
+  just the variable name, without a value
+
 
 0.23.1 [2021-08-17]
 ----------------------

kitty/child.py

@@ -13,7 +13,7 @@ from typing import (
 
 import kitty.fast_data_types as fast_data_types
 
-from .constants import is_macos, shell_path, terminfo_dir
+from .constants import is_macos, shell_path, terminfo_dir, delete_env_var
 from .types import run_once
 
 try:
@@ -232,6 +232,7 @@ class Child:
                 from .shell_integration import get_supported_shell_name
                 if get_supported_shell_name(self.argv[0]):
                     env['KITTY_SHELL_INTEGRATION'] = opts.shell_integration
+            env = {k: v for k, v in env.items() if v is not delete_env_var}
         return env
 
     def fork(self) -> Optional[int]:

kitty/constants.py

@@ -21,10 +21,18 @@ class Version(NamedTuple):
     patch: int
 
 
+class SentinelString(str):
+
+    def __new__(cls, val: str) -> 'SentinelString':
+        ans: SentinelString = str.__new__(cls, val)
+        return ans
+
+
 appname: str = 'kitty'
 kitty_face = '🐱'
 version: Version = Version(0, 23, 1)
 str_version: str = '.'.join(map(str, version))
+delete_env_var = SentinelString('_delete_this_env_var_')
 _plat = sys.platform.lower()
 is_macos: bool = 'darwin' in _plat
 if getattr(sys, 'frozen', False):

kitty/launch.py

@@ -17,6 +17,7 @@ from .tabs import Tab
 from .types import run_once
 from .utils import find_exe, read_shell_environment, set_primary_selection
 from .window import Watchers, Window
+from .options.utils import env as parse_env
 
 try:
     from typing import TypedDict
@@ -69,8 +70,9 @@ The working directory for the newly launched child. Use the special value
 --env
 type=list
 Environment variables to set in the child process. Can be specified multiple
-times to set different environment variables.
-Syntax: :italic:`name=value`.
+times to set different environment variables.  Syntax: :code:`name=value`.
+Using :code:`name=` will set to empty string and just :code:`name` will
+remove the environment variable.
 
 
 --copy-colors
@@ -193,9 +195,8 @@ def get_env(opts: LaunchCLIOptions, active_child: Child) -> Dict[str, str]:
     if opts.copy_env and active_child:
         env.update(active_child.foreground_environ)
     for x in opts.env:
-        parts = x.split('=', 1)
-        if len(parts) == 2:
-            env[parts[0]] = parts[1]
+        for k, v in parse_env(x, env):
+            env[k] = v
     return env
 
 

kitty/options/definition.py

@@ -2518,7 +2518,9 @@ environment variables are expanded recursively, so if you use::
     env MYVAR1=a
     env MYVAR2=${MYVAR1}/${HOME}/b
 
-The value of MYVAR2 will be :code:`a/<path to home directory>/b`.
+The value of MYVAR2 will be :code:`a/<path to home directory>/b`. Using
+:code:`VAR=` will set it to the empty string and using just :code:`VAR`
+will delete the variable from the child process' environment.
 '''
     )
 

kitty/options/utils.py

@@ -16,7 +16,7 @@ from kitty.conf.utils import (
     KeyAction, key_func, positive_float, positive_int, python_string, to_bool,
     to_cmdline, to_color, uniq, unit_float
 )
-from kitty.constants import config_dir, is_macos
+from kitty.constants import config_dir, is_macos, delete_env_var
 from kitty.fast_data_types import CURSOR_BEAM, CURSOR_BLOCK, CURSOR_UNDERLINE
 from kitty.fonts import FontFeature
 from kitty.key_names import (
@@ -731,10 +731,17 @@ def font_features(val: str) -> Iterable[Tuple[str, Tuple[FontFeature, ...]]]:
 
 
 def env(val: str, current_val: Dict[str, str]) -> Iterable[Tuple[str, str]]:
-    key, val = val.partition('=')[::2]
-    key, val = key.strip(), val.strip()
-    if key:
-        yield key, expandvars(val, current_val)
+    val = val.strip()
+    if val:
+        if '=' in val:
+            key, v = val.split('=', 1)
+            key, v = key.strip(), v.strip()
+            if key:
+                if v:
+                    v = expandvars(v, current_val)
+                yield key, v
+        else:
+            yield val, delete_env_var
 
 
 def kitten_alias(val: str) -> Iterable[Tuple[str, List[str]]]:

kitty_tests/options.py

@@ -5,6 +5,7 @@
 
 from . import BaseTest
 from kitty.utils import log_error
+from kitty.constants import delete_env_var
 
 
 class TestConfParsing(BaseTest):
@@ -48,8 +49,8 @@ class TestConfParsing(BaseTest):
         self.assertFalse(bad_lines)
         opts = p('pointer_shape_when_grabbed XXX', bad_line_num=1)
         self.ae(opts.pointer_shape_when_grabbed, defaults.pointer_shape_when_grabbed)
-        opts = p('env A=1', 'env B=x$A', 'clear_all_shortcuts y', 'kitten_alias a b --moo', 'map f1 kitten a')
-        self.ae(opts.env, {'A': '1', 'B': 'x1'})
+        opts = p('env A=1', 'env B=x$A', 'env C=', 'env D', 'clear_all_shortcuts y', 'kitten_alias a b --moo', 'map f1 kitten a')
+        self.ae(opts.env, {'A': '1', 'B': 'x1', 'C': '', 'D': delete_env_var})
         ka = tuple(opts.keymap.values())[0]
         self.ae(ka.args, ('b', '--moo'))
         opts = p('kitty_mod alt')