initial foreign shell trial

xonsh/foreign_shells.py

@@ -0,0 +1,116 @@
+"""Tools to help interface with foreign shells, such as Bash."""
+import re
+import shlex
+import builtins
+import subprocess
+from warnings import warn
+from functools import lru_cache
+
+
+COMMAND = """
+echo __XONSH_ENV_BEG__
+{envcmd}
+echo __XONSH_ENV_END__
+echo __XONSH_ALIAS_BEG__
+{aliascmd}
+echo __XONSH_ALIAS_END__
+""".strip()
+
+FAILED_COMMAND_STDOUT = """
+__XONSH_ENV_BEG__
+__XONSH_ENV_END__
+__XONSH_ALIAS_BEG__
+__XONSH_ALIAS_END__
+""".strip()
+
+@lru_cache()
+def foreign_shell_data(shell, interactive=True, login=False, envcmd='env', 
+                       aliascmd='alias', extra_args=(), currenv=None):
+    """Extracts data from a foreign (non-xonsh) shells. Currently this gets 
+    the environment and aliases, but may be extended in the future.
+
+    Parameters
+    ----------
+    shell : str
+        The name of the shell, such as 'bash' or '/bin/sh'.
+    login : bool, optional
+        Whether the shell should be run in interactive mode.
+    login : bool, optional
+        Whether the shell should be a login shell.
+    envcmd : str, optional
+        The command to generate environment output with.
+    aliascmd : str, optional
+        The command to generate alais output with.
+    extra_args : list of str, optional
+        Addtional command line options to pass into the shell.
+    currenv : dict or None, optional
+        Manual override for the current environment.
+
+    Returns
+    -------
+    env : dict
+        Dictionary of shell's environment
+    aliases : dict
+        Dictionary of shell's alaiases.
+    """
+    cmd = [shell]
+    if interactive:
+        cmd.append('-i')
+    if login:
+        cmd.append('-l')
+    cmd.extend(extra_args)
+    cmd.append('-c')
+    cmd.append(COMMAND.format(envcmd=envcmd, aliascmd=aliascmd))
+    if currenv is None and hasattr(builtins, '__xonsh_env__'):
+        currenv = builtins.__xonsh_env__.detype()
+    try:
+        s = subprocess.check_output(cmd,stderr=subprocess.PIPE, env=currenv,
+                                    universal_newlines=True)
+    except (subprocess.CalledProcessError, FileNotFoundError):
+        s = FAILED_COMMAND_STDOUT
+    env = parse_env(s)
+    aliases = parse_aliases(s)
+    return env, aliases
+
+
+ENV_RE = re.compile('__XONSH_ENV_BEG__\n(.*)__XONSH_ENV_END__', flags=re.DOTALL)
+
+def parse_env(s):
+    """Parses the environment portion of string into a dict."""
+    m = ENV_RE.search(s)
+    if m is None:
+        return {}
+    g1 = m.group(1)
+    items = [line.split('=', 1) for line in g1.splitlines() if '=' in line]
+    env = dict(items)
+    return env
+
+
+ALIAS_RE = re.compile('__XONSH_ALIAS_BEG__\n(.*)__XONSH_ALIAS_END__', 
+                      flags=re.DOTALL)
+
+def parse_aliases(s):
+    """Parses the aliases portion of string into a dict."""
+    m = ALIAS_RE.search(s)
+    if m is None:
+        return {}
+    g1 = m.group(1)
+    items = [line.split('=', 1) for line in g1.splitlines() if \
+             line.startswith('alias ') and '=' in line]
+    aliases = {}
+    for key, value in items:
+        try:
+            key = key[6:]  # lstrip 'alias '
+            # undo bash's weird quoting of single quotes (sh_single_quote)
+            value = value.replace('\'\\\'\'', '\'')
+            # strip one single quote at the start and end of value
+            if value[0] == '\'' and value[-1] == '\'':
+                value = value[1:-1]
+            value = shlex.split(value)
+        except ValueError as exc:
+            warn('could not parse alias "{0}": {1!r}'.format(key, exc),
+                 RuntimeWarning)
+            continue
+        aliases[key] = value
+    return aliases
+