prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Bad documentation or bug: _.rtn does not work
  [In the Documentation](https://xon.sh/bash_to_xsh.html) you write that `_.rtn` is the equivalent of the shell `$?` and that it `Returns the exit code, or status, of the previous command.`. Either I understand the documentation wrong or there is a bug:
  ```
  #!/usr/bin/env xonsh
  echo "abc"
  print(_.rtn)
  ```
  Outputs
  ```
  abc
  Traceback (most recent call last):
    File "/home/volker/.local/bin/xonsh", line 8, in <module>
      sys.exit(main())
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py", line 426, in main
      _failback_to_other_shells(args, err)
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py", line 373, in _failback_to_other_shells
      raise err
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py", line 424, in main
      sys.exit(main_xonsh(args))
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py", line 471, in main_xonsh
      run_script_with_cache(
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/codecache.py", line 162, in run_script_with_cache
      run_compiled_code(ccode, glb, loc, mode)
    File "/home/volker/.local/lib/python3.8/site-packages/xonsh/codecache.py", line 67, in run_compiled_code
      func(code, glb, loc)
    File "./generateIso.xonsh", line 24, in <module>
      print(_.rtn)
  NameError: name '_' is not defined
  ```
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `xontrib/bashisms.py`
  Content:
  ```
  1 """Bash-like interface extensions for xonsh."""
  2 import shlex
  3 import sys
  4 import re
  5 import builtins
  6 
  7 
  8 __all__ = ()
  9 
  10 
  11 @events.on_transform_command
  12 def bash_preproc(cmd, **kw):
  13     bang_previous = {
  14         "!": lambda x: x,
  15         "$": lambda x: shlex.split(x)[-1],
  16         "^": lambda x: shlex.split(x)[0],
  17         "*": lambda x: " ".join(shlex.split(x)[1:]),
  18     }
  19 
  20     def replace_bang(m):
  21         arg = m.group(1)
  22         inputs = __xonsh__.history.inps
  23 
  24         # Dissect the previous command.
  25         if arg in bang_previous:
  26             try:
  27                 return bang_previous[arg](inputs[-1])
  28             except IndexError:
  29                 print("xonsh: no history for '!{}'".format(arg))
  30                 return ""
  31 
  32         # Look back in history for a matching command.
  33         else:
  34             try:
  35                 return next((x for x in reversed(inputs) if x.startswith(arg)))
  36             except StopIteration:
  37                 print("xonsh: no previous commands match '!{}'".format(arg))
  38                 return ""
  39 
  40     return re.sub(r"!([!$^*]|[\w]+)", replace_bang, cmd)
  41 
  42 
  43 def alias(args, stdin=None):
  44     ret = 0
  45 
  46     if args:
  47         for arg in args:
  48             if "=" in arg:
  49                 # shlex.split to remove quotes, e.g. "foo='echo hey'" into
  50                 # "foo=echo hey"
  51                 name, cmd = shlex.split(arg)[0].split("=", 1)
  52                 aliases[name] = shlex.split(cmd)
  53             elif arg in aliases:
  54                 print("{}={}".format(arg, aliases[arg]))
  55             else:
  56                 print("alias: {}: not found".format(arg), file=sys.stderr)
  57                 ret = 1
  58     else:
  59         for alias, cmd in aliases.items():
  60             print("{}={}".format(alias, cmd))
  61 
  62     return ret
  63 
  64 
  65 aliases["alias"] = alias
  66 builtins.__xonsh__.env["THREAD_SUBPROCS"] = False
  67
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/xontrib/bashisms.py b/xontrib/bashisms.py
  --- a/xontrib/bashisms.py
  +++ b/xontrib/bashisms.py
  @@ -64,3 +64,86 @@
   
   aliases["alias"] = alias
   builtins.__xonsh__.env["THREAD_SUBPROCS"] = False
  +
  +
  +def _unset(args):
  +    if not args:
  +        print("Usage: unset ENV_VARIABLE", file=sys.stderr)
  +
  +    for v in args:
  +        try:
  +            __xonsh__.env.pop(v)
  +        except KeyError:
  +            print(f"{v} not found", file=sys.stderr)
  +
  +
  +aliases["unset"] = _unset
  +
  +
  +def _export(args):
  +    if not args:
  +        print("Usage: export ENV_VARIABLE=VALUE", file=sys.stderr)
  +
  +    for eq in args:
  +        if "=" in eq:
  +            name, val = shlex.split(eq)[0].split("=", 1)
  +            __xonsh__.env[name] = val
  +        else:
  +            print(f"{eq} equal sign not found", file=sys.stderr)
  +
  +
  +aliases["export"] = _export
  +
  +
  +def _set(args):
  +    arg = args[0]
  +    if arg == "-e":
  +        __xonsh__.env["RAISE_SUBPROC_ERROR"] = True
  +    elif arg == "+e":
  +        __xonsh__.env["RAISE_SUBPROC_ERROR"] = False
  +    elif arg == "-x":
  +        __xonsh__.env["XONSH_TRACE_SUBPROC"] = True
  +    elif arg == "+x":
  +        __xonsh__.env["XONSH_TRACE_SUBPROC"] = False
  +    else:
  +        print(
  +            "Not supported in xontrib bashisms.\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py",
  +            file=sys.stderr,
  +        )
  +
  +
  +aliases["set"] = _set
  +
  +
  +def _shopt(args):
  +
  +    supported_shopt = ["DOTGLOB"]
  +
  +    args_len = len(args)
  +    if args_len == 0:
  +        for so in supported_shopt:
  +            onoff = "on" if so in __xonsh__.env and __xonsh__.env[so] else "off"
  +            print(f"dotglob\t{onoff}")
  +        return
  +    elif args_len < 2 or args[0] in ["-h", "--help"]:
  +        print(f'Usage: shopt <-s|-u> <{"|".join(supported_shopt).lower()}>')
  +        return
  +
  +    opt = args[0]
  +    optname = args[1]
  +
  +    if opt == "-s" and optname == "dotglob":
  +        __xonsh__.env["DOTGLOB"] = True
  +    elif opt == "-u" and optname == "dotglob":
  +        __xonsh__.env["DOTGLOB"] = False
  +    else:
  +        print(
  +            "Not supported in xontrib bashisms.\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py",
  +            file=sys.stderr,
  +        )
  +
  +
  +aliases["shopt"] = _shopt
  +
  +
  +aliases["complete"] = "completer list"
  
verification_info: {"golden_diff": "diff --git a/xontrib/bashisms.py b/xontrib/bashisms.py\n--- a/xontrib/bashisms.py\n+++ b/xontrib/bashisms.py\n@@ -64,3 +64,86 @@\n \n aliases[\"alias\"] = alias\n builtins.__xonsh__.env[\"THREAD_SUBPROCS\"] = False\n+\n+\n+def _unset(args):\n+    if not args:\n+        print(\"Usage: unset ENV_VARIABLE\", file=sys.stderr)\n+\n+    for v in args:\n+        try:\n+            __xonsh__.env.pop(v)\n+        except KeyError:\n+            print(f\"{v} not found\", file=sys.stderr)\n+\n+\n+aliases[\"unset\"] = _unset\n+\n+\n+def _export(args):\n+    if not args:\n+        print(\"Usage: export ENV_VARIABLE=VALUE\", file=sys.stderr)\n+\n+    for eq in args:\n+        if \"=\" in eq:\n+            name, val = shlex.split(eq)[0].split(\"=\", 1)\n+            __xonsh__.env[name] = val\n+        else:\n+            print(f\"{eq} equal sign not found\", file=sys.stderr)\n+\n+\n+aliases[\"export\"] = _export\n+\n+\n+def _set(args):\n+    arg = args[0]\n+    if arg == \"-e\":\n+        __xonsh__.env[\"RAISE_SUBPROC_ERROR\"] = True\n+    elif arg == \"+e\":\n+        __xonsh__.env[\"RAISE_SUBPROC_ERROR\"] = False\n+    elif arg == \"-x\":\n+        __xonsh__.env[\"XONSH_TRACE_SUBPROC\"] = True\n+    elif arg == \"+x\":\n+        __xonsh__.env[\"XONSH_TRACE_SUBPROC\"] = False\n+    else:\n+        print(\n+            \"Not supported in xontrib bashisms.\\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py\",\n+            file=sys.stderr,\n+        )\n+\n+\n+aliases[\"set\"] = _set\n+\n+\n+def _shopt(args):\n+\n+    supported_shopt = [\"DOTGLOB\"]\n+\n+    args_len = len(args)\n+    if args_len == 0:\n+        for so in supported_shopt:\n+            onoff = \"on\" if so in __xonsh__.env and __xonsh__.env[so] else \"off\"\n+            print(f\"dotglob\\t{onoff}\")\n+        return\n+    elif args_len < 2 or args[0] in [\"-h\", \"--help\"]:\n+        print(f'Usage: shopt <-s|-u> <{\"|\".join(supported_shopt).lower()}>')\n+        return\n+\n+    opt = args[0]\n+    optname = args[1]\n+\n+    if opt == \"-s\" and optname == \"dotglob\":\n+        __xonsh__.env[\"DOTGLOB\"] = True\n+    elif opt == \"-u\" and optname == \"dotglob\":\n+        __xonsh__.env[\"DOTGLOB\"] = False\n+    else:\n+        print(\n+            \"Not supported in xontrib bashisms.\\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py\",\n+            file=sys.stderr,\n+        )\n+\n+\n+aliases[\"shopt\"] = _shopt\n+\n+\n+aliases[\"complete\"] = \"completer list\"\n", "issue": "Bad documentation or bug: _.rtn does not work\n[In the Documentation](https://xon.sh/bash_to_xsh.html) you write that `_.rtn` is the equivalent of the shell `$?` and that it `Returns the exit code, or status, of the previous command.`. Either I understand the documentation wrong or there is a bug:\r\n```\r\n#!/usr/bin/env xonsh\r\necho \"abc\"\r\nprint(_.rtn)\r\n```\r\nOutputs\r\n```\r\nabc\r\nTraceback (most recent call last):\r\n  File \"/home/volker/.local/bin/xonsh\", line 8, in <module>\r\n    sys.exit(main())\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py\", line 426, in main\r\n    _failback_to_other_shells(args, err)\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py\", line 373, in _failback_to_other_shells\r\n    raise err\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py\", line 424, in main\r\n    sys.exit(main_xonsh(args))\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/main.py\", line 471, in main_xonsh\r\n    run_script_with_cache(\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/codecache.py\", line 162, in run_script_with_cache\r\n    run_compiled_code(ccode, glb, loc, mode)\r\n  File \"/home/volker/.local/lib/python3.8/site-packages/xonsh/codecache.py\", line 67, in run_compiled_code\r\n    func(code, glb, loc)\r\n  File \"./generateIso.xonsh\", line 24, in <module>\r\n    print(_.rtn)\r\nNameError: name '_' is not defined\r\n```\n", "before_files": [{"content": "\"\"\"Bash-like interface extensions for xonsh.\"\"\"\nimport shlex\nimport sys\nimport re\nimport builtins\n\n\n__all__ = ()\n\n\n@events.on_transform_command\ndef bash_preproc(cmd, **kw):\n    bang_previous = {\n        \"!\": lambda x: x,\n        \"$\": lambda x: shlex.split(x)[-1],\n        \"^\": lambda x: shlex.split(x)[0],\n        \"*\": lambda x: \" \".join(shlex.split(x)[1:]),\n    }\n\n    def replace_bang(m):\n        arg = m.group(1)\n        inputs = __xonsh__.history.inps\n\n        # Dissect the previous command.\n        if arg in bang_previous:\n            try:\n                return bang_previous[arg](inputs[-1])\n            except IndexError:\n                print(\"xonsh: no history for '!{}'\".format(arg))\n                return \"\"\n\n        # Look back in history for a matching command.\n        else:\n            try:\n                return next((x for x in reversed(inputs) if x.startswith(arg)))\n            except StopIteration:\n                print(\"xonsh: no previous commands match '!{}'\".format(arg))\n                return \"\"\n\n    return re.sub(r\"!([!$^*]|[\\w]+)\", replace_bang, cmd)\n\n\ndef alias(args, stdin=None):\n    ret = 0\n\n    if args:\n        for arg in args:\n            if \"=\" in arg:\n                # shlex.split to remove quotes, e.g. \"foo='echo hey'\" into\n                # \"foo=echo hey\"\n                name, cmd = shlex.split(arg)[0].split(\"=\", 1)\n                aliases[name] = shlex.split(cmd)\n            elif arg in aliases:\n                print(\"{}={}\".format(arg, aliases[arg]))\n            else:\n                print(\"alias: {}: not found\".format(arg), file=sys.stderr)\n                ret = 1\n    else:\n        for alias, cmd in aliases.items():\n            print(\"{}={}\".format(alias, cmd))\n\n    return ret\n\n\naliases[\"alias\"] = alias\nbuiltins.__xonsh__.env[\"THREAD_SUBPROCS\"] = False\n", "path": "xontrib/bashisms.py"}], "after_files": [{"content": "\"\"\"Bash-like interface extensions for xonsh.\"\"\"\nimport shlex\nimport sys\nimport re\nimport builtins\n\n\n__all__ = ()\n\n\n@events.on_transform_command\ndef bash_preproc(cmd, **kw):\n    bang_previous = {\n        \"!\": lambda x: x,\n        \"$\": lambda x: shlex.split(x)[-1],\n        \"^\": lambda x: shlex.split(x)[0],\n        \"*\": lambda x: \" \".join(shlex.split(x)[1:]),\n    }\n\n    def replace_bang(m):\n        arg = m.group(1)\n        inputs = __xonsh__.history.inps\n\n        # Dissect the previous command.\n        if arg in bang_previous:\n            try:\n                return bang_previous[arg](inputs[-1])\n            except IndexError:\n                print(\"xonsh: no history for '!{}'\".format(arg))\n                return \"\"\n\n        # Look back in history for a matching command.\n        else:\n            try:\n                return next((x for x in reversed(inputs) if x.startswith(arg)))\n            except StopIteration:\n                print(\"xonsh: no previous commands match '!{}'\".format(arg))\n                return \"\"\n\n    return re.sub(r\"!([!$^*]|[\\w]+)\", replace_bang, cmd)\n\n\ndef alias(args, stdin=None):\n    ret = 0\n\n    if args:\n        for arg in args:\n            if \"=\" in arg:\n                # shlex.split to remove quotes, e.g. \"foo='echo hey'\" into\n                # \"foo=echo hey\"\n                name, cmd = shlex.split(arg)[0].split(\"=\", 1)\n                aliases[name] = shlex.split(cmd)\n            elif arg in aliases:\n                print(\"{}={}\".format(arg, aliases[arg]))\n            else:\n                print(\"alias: {}: not found\".format(arg), file=sys.stderr)\n                ret = 1\n    else:\n        for alias, cmd in aliases.items():\n            print(\"{}={}\".format(alias, cmd))\n\n    return ret\n\n\naliases[\"alias\"] = alias\nbuiltins.__xonsh__.env[\"THREAD_SUBPROCS\"] = False\n\n\ndef _unset(args):\n    if not args:\n        print(\"Usage: unset ENV_VARIABLE\", file=sys.stderr)\n\n    for v in args:\n        try:\n            __xonsh__.env.pop(v)\n        except KeyError:\n            print(f\"{v} not found\", file=sys.stderr)\n\n\naliases[\"unset\"] = _unset\n\n\ndef _export(args):\n    if not args:\n        print(\"Usage: export ENV_VARIABLE=VALUE\", file=sys.stderr)\n\n    for eq in args:\n        if \"=\" in eq:\n            name, val = shlex.split(eq)[0].split(\"=\", 1)\n            __xonsh__.env[name] = val\n        else:\n            print(f\"{eq} equal sign not found\", file=sys.stderr)\n\n\naliases[\"export\"] = _export\n\n\ndef _set(args):\n    arg = args[0]\n    if arg == \"-e\":\n        __xonsh__.env[\"RAISE_SUBPROC_ERROR\"] = True\n    elif arg == \"+e\":\n        __xonsh__.env[\"RAISE_SUBPROC_ERROR\"] = False\n    elif arg == \"-x\":\n        __xonsh__.env[\"XONSH_TRACE_SUBPROC\"] = True\n    elif arg == \"+x\":\n        __xonsh__.env[\"XONSH_TRACE_SUBPROC\"] = False\n    else:\n        print(\n            \"Not supported in xontrib bashisms.\\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py\",\n            file=sys.stderr,\n        )\n\n\naliases[\"set\"] = _set\n\n\ndef _shopt(args):\n\n    supported_shopt = [\"DOTGLOB\"]\n\n    args_len = len(args)\n    if args_len == 0:\n        for so in supported_shopt:\n            onoff = \"on\" if so in __xonsh__.env and __xonsh__.env[so] else \"off\"\n            print(f\"dotglob\\t{onoff}\")\n        return\n    elif args_len < 2 or args[0] in [\"-h\", \"--help\"]:\n        print(f'Usage: shopt <-s|-u> <{\"|\".join(supported_shopt).lower()}>')\n        return\n\n    opt = args[0]\n    optname = args[1]\n\n    if opt == \"-s\" and optname == \"dotglob\":\n        __xonsh__.env[\"DOTGLOB\"] = True\n    elif opt == \"-u\" and optname == \"dotglob\":\n        __xonsh__.env[\"DOTGLOB\"] = False\n    else:\n        print(\n            \"Not supported in xontrib bashisms.\\nPRs are welcome - https://github.com/xonsh/xonsh/blob/master/xontrib/bashisms.py\",\n            file=sys.stderr,\n        )\n\n\naliases[\"shopt\"] = _shopt\n\n\naliases[\"complete\"] = \"completer list\"\n", "path": "xontrib/bashisms.py"}]}