Improve some utility functions

Make expandvars accept both $VARNAME and ${VARNAME} now matches
the behavior of posixpath.expandvars

Allow overriding the environment variables to_cmdline expands against

kitty/conf/utils.py

@@ -11,7 +11,7 @@ from typing import (
 )
 
 from ..rgb import Color, to_color as as_color
-from ..utils import log_error
+from ..utils import log_error, expandvars
 
 key_pat = re.compile(r'([a-zA-Z][a-zA-Z0-9_-]*)\s+(.+)$')
 T = TypeVar('T')
@@ -53,13 +53,36 @@ def to_bool(x: str) -> bool:
     return x.lower() in ('y', 'yes', 'true')
 
 
-def to_cmdline(x: str) -> List[str]:
-    return list(
-        map(
-            lambda y: os.path.expandvars(os.path.expanduser(y)),
-            shlex.split(x)
+class ToCmdline:
+
+    def __init__(self) -> None:
+        self.override_env: Optional[Dict[str, str]] = None
+
+    def __enter__(self) -> 'ToCmdline':
+        return self
+
+    def __exit__(self, *a: Any) -> None:
+        self.override_env = None
+
+    def filter_env_vars(self, *a: str) -> 'ToCmdline':
+        remove = frozenset(a)
+        self.override_env = {k: v for k, v in os.environ.items() if k not in remove}
+        return self
+
+    def __call__(self, x: str) -> List[str]:
+        return list(
+            map(
+                lambda y: expandvars(
+                    os.path.expanduser(y),
+                    os.environ if self.override_env is None else self.override_env,
+                    fallback_to_os_env=False
+                ),
+                shlex.split(x)
+            )
         )
-    )
+
+
+to_cmdline = ToCmdline()
 
 
 def python_string(text: str) -> str:

kitty/config_data.py

@@ -13,7 +13,7 @@ from typing import (
 from . import fast_data_types as defines
 from .conf.definition import Option, Shortcut, option_func
 from .conf.utils import (
-    choices, positive_float, positive_int, to_bool, to_cmdline, to_color,
+    choices, positive_float, positive_int, to_bool, to_cmdline as tc, to_color,
     to_color_or_none, unit_float
 )
 from .constants import FloatEdges, config_dir, is_macos
@@ -29,6 +29,10 @@ mod_map = {'CTRL': 'CONTROL', 'CMD': 'SUPER', '⌘': 'SUPER',
            '⌥': 'ALT', 'OPTION': 'ALT', 'KITTY_MOD': 'KITTY'}
 
 
+def to_cmdline(x: str) -> List[str]:
+    return tc(x)
+
+
 def parse_mods(parts: Iterable[str], sc: str) -> Optional[int]:
 
     def map_mod(m: str) -> str:

kitty/utils.py

@@ -14,7 +14,7 @@ from contextlib import suppress
 from functools import lru_cache
 from time import monotonic
 from typing import (
-    Any, Callable, Dict, Generator, Iterable, List, Match, NamedTuple,
+    Any, Callable, Dict, Generator, Iterable, List, Mapping, Match, NamedTuple,
     Optional, Tuple, Union, cast
 )
 
@@ -28,18 +28,21 @@ from .typing import AddressFamily, PopenType, Socket, StartupCtx
 BASE = os.path.dirname(os.path.abspath(__file__))
 
 
-def expandvars(val: str, env: Dict[str, str] = {}) -> str:
+def expandvars(val: str, env: Mapping[str, str] = {}, fallback_to_os_env: bool = True) -> str:
 
     def sub(m: Match) -> str:
-        key = m.group(1)
+        key = m.group(1) or m.group(2)
         result = env.get(key)
-        if result is None:
+        if result is None and fallback_to_os_env:
             result = os.environ.get(key)
         if result is None:
             result = m.group()
         return result
 
-    return re.sub(r'\$\{(\S+?)\}', sub, val)
+    if '$' not in val:
+        return val
+
+    return re.sub(r'\$(?:(\w+)|\{([^}]+)\})', sub, val)
 
 
 def platform_window_id(os_window_id: int) -> Optional[int]:
@@ -561,7 +564,7 @@ def read_shell_environment(opts: Optional[Options] = None) -> Dict[str, str]:
 
 def parse_uri_list(text: str) -> Generator[str, None, None]:
     ' Get paths from file:// URLs '
-    from urllib.parse import urlparse, unquote
+    from urllib.parse import unquote, urlparse
     for line in text.splitlines():
         if not line or line.startswith('#'):
             continue