Source code for xonsh.commands_cache

# -*- coding: utf-8 -*-
"""Module for caching command & alias names as well as for predicting whether
a command will be able to be run in the background.

A background predictor is a function that accepts a single argument list
and returns whethere or not the process can be run in the background (returns
True) or must be run the foreground (returns False).
import os
import time
import builtins
import argparse
import as cabc

from xonsh.platform import ON_WINDOWS, ON_POSIX, pathbasename
from import executables_in
from xonsh.lazyasd import lazyobject

[docs]class CommandsCache(cabc.Mapping): """A lazy cache representing the commands available on the file system. The keys are the command names and the values a tuple of (loc, has_alias) where loc is either a str pointing to the executable on the file system or None (if no executable exists) and has_alias is a boolean flag for whether the command has an alias. """ def __init__(self): self._cmds_cache = {} self._path_checksum = None self._alias_checksum = None self._path_mtime = -1 self.threadable_predictors = default_threadable_predictors() def __contains__(self, key): _ = self.all_commands return self.lazyin(key) def __iter__(self): for cmd, (path, is_alias) in self.all_commands.items(): if ON_WINDOWS and path is not None: # All comand keys are stored in uppercase on Windows. # This ensures the original command name is returned. cmd = pathbasename(path) yield cmd def __len__(self): return len(self.all_commands) def __getitem__(self, key): _ = self.all_commands return self.lazyget(key)
[docs] def is_empty(self): """Returns whether the cache is populated or not.""" return len(self._cmds_cache) == 0
[docs] def get_possible_names(name): """Generates the possible `PATHEXT` extension variants of a given executable name on Windows as a list, conserving the ordering in `PATHEXT`. Returns a list as `name` being the only item in it on other platforms.""" if ON_WINDOWS: pathext = builtins.__xonsh_env__.get('PATHEXT') name = name.upper() return [ name + ext for ext in ([''] + pathext) ] else: return [name]
@property def all_commands(self): paths = builtins.__xonsh_env__.get('PATH', []) pathset = frozenset(x for x in paths if os.path.isdir(x)) # did PATH change? path_hash = hash(pathset) cache_valid = path_hash == self._path_checksum self._path_checksum = path_hash # did aliases change? alss = getattr(builtins, 'aliases', dict()) al_hash = hash(frozenset(alss)) cache_valid = cache_valid and al_hash == self._alias_checksum self._alias_checksum = al_hash # did the contents of any directory in PATH change? max_mtime = 0 for path in pathset: mtime = os.stat(path).st_mtime if mtime > max_mtime: max_mtime = mtime cache_valid = cache_valid and (max_mtime <= self._path_mtime) self._path_mtime = max_mtime if cache_valid: return self._cmds_cache allcmds = {} for path in reversed(paths): # iterate backwards so that entries at the front of PATH overwrite # entries at the back. for cmd in executables_in(path): key = cmd.upper() if ON_WINDOWS else cmd allcmds[key] = (os.path.join(path, cmd), alss.get(key, None)) for cmd in alss: if cmd not in allcmds: key = cmd.upper() if ON_WINDOWS else cmd allcmds[key] = (cmd, True) self._cmds_cache = allcmds return allcmds
[docs] def cached_name(self, name): """Returns the name that would appear in the cache, if it exists.""" if name is None: return None cached = pathbasename(name) if ON_WINDOWS: keys = self.get_possible_names(cached) cached = next((k for k in keys if k in self._cmds_cache), None) return cached
[docs] def lazyin(self, key): """Checks if the value is in the current cache without the potential to update the cache. It just says whether the value is known *now*. This may not reflect precisely what is on the $PATH. """ return self.cached_name(key) in self._cmds_cache
[docs] def lazyiter(self): """Returns an iterator over the current cache contents without the potential to update the cache. This may not reflect what is on the $PATH. """ return iter(self._cmds_cache)
[docs] def lazylen(self): """Returns the length of the current cache contents without the potential to update the cache. This may not reflect precisely what is on the $PATH. """ return len(self._cmds_cache)
[docs] def lazyget(self, key, default=None): """A lazy value getter.""" return self._cmds_cache.get(self.cached_name(key), default)
[docs] def locate_binary(self, name, ignore_alias=False): """Locates an executable on the file system using the cache. Arguments --------- name : str name of binary to search for ignore_alias : bool, optional Force return of binary path even if alias of ``name`` exists (default ``False``) """ # make sure the cache is up to date by accessing the property _ = self.all_commands return self.lazy_locate_binary(name, ignore_alias)
[docs] def lazy_locate_binary(self, name, ignore_alias=False): """Locates an executable in the cache, without checking its validity. Arguments --------- name : str name of binary to search for ignore_alias : bool, optional Force return of binary path even if alias of ``name`` exists (default ``False``) """ possibilities = self.get_possible_names(name) if ON_WINDOWS: # Windows users expect to be able to execute files in the same # directory without `./` local_bin = next((fn for fn in possibilities if os.path.isfile(fn)), None) if local_bin: return os.path.abspath(local_bin) cached = next((cmd for cmd in possibilities if cmd in self._cmds_cache), None) if cached: (path, alias) = self._cmds_cache[cached] if not alias or ignore_alias: return path else: return None elif os.path.isfile(name) and name != pathbasename(name): return name
[docs] def predict_threadable(self, cmd): """Predicts whether a command list is able to be run on a background thread, rather than the main thread. """ name = self.cached_name(cmd[0]) predictors = self.threadable_predictors if ON_WINDOWS: # On all names (keys) are stored in upper case so instead # we get the original cmd or alias name path, _ = self.lazyget(name, (None, None)) if path is None: return True else: name = pathbasename(path) if name not in predictors: pre, ext = os.path.splitext(name) if pre in predictors: predictors[name] = predictors[pre] if name not in predictors: predictors[name] = self.default_predictor(name, cmd[0]) predictor = predictors[name] return predictor(cmd[1:])
# # Background Predictors (as methods) #
[docs] def default_predictor(self, name, cmd0): if ON_POSIX: return self.default_predictor_readbin(name, cmd0, timeout=0.1, failure=predict_true) else: return predict_true
[docs] def default_predictor_readbin(self, name, cmd0, timeout, failure): """Make a defautt predictor by analyzing the content of the binary. Should only works on POSIX. Return failure if the analysis fails. """ fname = cmd0 if os.path.isabs(cmd0) else None fname = cmd0 if fname is None and os.sep in cmd0 else fname fname = self.lazy_locate_binary(name) if fname is None else fname if fname is None: return failure if not os.path.isfile(fname): return failure try: fd =, os.O_RDONLY | os.O_NONBLOCK) except Exception: return failure # opening error search_for = { (b'ncurses',): [False, ], (b'isatty', b'tcgetattr', b'tcsetattr'): [False, False, False], } tstart = time.time() block = b'' while time.time() < tstart + timeout: previous_block = block try: block =, 2048) except Exception: # should not occur, except e.g. if a file is deleted a a dir is # created with the same name between os.path.isfile and os.close(fd) return failure if len(block) == 0: os.close(fd) return predict_true # no keys of search_for found analyzed_block = previous_block + block for k, v in search_for.items(): for i in range(len(k)): if v[i]: continue if k[i] in analyzed_block: v[i] = True if all(v): os.close(fd) return predict_false # use one key of search_for os.close(fd) return failure # timeout
# # Background Predictors #
[docs]def predict_true(args): """Always say the process is threadable.""" return True
[docs]def predict_false(args): """Never say the process is threadable.""" return False
@lazyobject def SHELL_PREDICTOR_PARSER(): p = argparse.ArgumentParser('shell', add_help=False) p.add_argument('-c', nargs='?', default=None) p.add_argument('filename', nargs='?', default=None) return p
[docs]def predict_shell(args): """Precict the backgroundability of the normal shell interface, which comes down to whether it is being run in subproc mode. """ ns, _ = SHELL_PREDICTOR_PARSER.parse_known_args(args) if ns.c is None and ns.filename is None: pred = False else: pred = True return pred
@lazyobject def HELP_VER_PREDICTOR_PARSER(): p = argparse.ArgumentParser('cmd', add_help=False) p.add_argument('-h', '--help', dest='help', action='store_true', default=None) p.add_argument('-v', '-V', '--version', dest='version', action='store_true', default=None) return p
[docs]def predict_help_ver(args): """Precict the backgroundability of commands that have help & version switches: -h, --help, -v, -V, --version. If either of these options is present, the command is assumed to print to stdout normally and is therefore threadable. Otherwise, the command is assumed to not be threadable. This is useful for commands, like top, that normally enter alternate mode but may not in certain circumstances. """ ns, _ = HELP_VER_PREDICTOR_PARSER.parse_known_args(args) pred = is not None or ns.version is not None return pred
[docs]def default_threadable_predictors(): """Generates a new defaultdict for known threadable predictors. The default is to predict true. """ # alphabetical, for what it is worth. predictors = { 'bash': predict_shell, 'csh': predict_shell, 'clear': predict_false, 'cls': predict_false, 'cmd': predict_shell, 'ex': predict_false, 'fish': predict_shell, 'gvim': predict_help_ver, 'htop': predict_help_ver, 'ksh': predict_shell, 'less': predict_help_ver, 'man': predict_help_ver, 'more': predict_help_ver, 'mvim': predict_help_ver, 'mutt': predict_help_ver, 'nano': predict_help_ver, 'nvim': predict_false, 'ponysay': predict_help_ver, 'psql': predict_false, 'python': predict_shell, 'python2': predict_shell, 'python3': predict_shell, 'repo': predict_help_ver, 'ranger': predict_help_ver, 'rview': predict_false, 'rvim': predict_false, 'scp': predict_false, 'sh': predict_shell, 'ssh': predict_false, 'startx': predict_false, 'sudo': predict_help_ver, 'tcsh': predict_shell, 'telnet': predict_false, 'top': predict_help_ver, 'vi': predict_false, 'view': predict_false, 'vim': predict_false, 'vimpager': predict_help_ver, 'weechat': predict_help_ver, 'xclip': predict_help_ver, 'xo': predict_help_ver, 'xonsh': predict_shell, '': predict_shell, 'zsh': predict_shell, } return predictors