Loading rc in non-interactive login shell (#3422)

* Setting -l flag loads environment on non-interactive shell
* Added checking dash existance in sys.argv[0]
* Fixed -a switch behaviour
* Added tests for xexec
* Added test for python<3.7 on Windows
* Testing non existent command with mocked execvpe

.gitignore

@@ -36,6 +36,7 @@ pip-selfcheck.json
 bin/
 /lib/
 include/
+venv/
 
 # Mac
 .DS_Store

news/extended-exec.rst

@@ -0,0 +1,24 @@
+**Added:**
+
+* Added ``-l``, ``-c`` and ``-a`` options to ``xexec``, works now like ``exec``
+  in bash/zsh
+
+**Changed:**
+
+* ``-l`` switch works like bash, loads environment in non-interactive shell
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

tests/aliases/test_xexec.py

@@ -0,0 +1,84 @@
+import os
+import inspect
+import pytest
+import sys
+
+from xonsh.aliases import xexec
+
+
+@pytest.fixture
+def mockexecvpe(monkeypatch):
+    def mocked_execvpe(_command, _args, _env):
+        pass
+
+    monkeypatch.setattr(os, "execvpe", mocked_execvpe)
+
+
+def test_noargs(mockexecvpe):
+    assert xexec([]) == (None, "xonsh: exec: no args specified\n", 1)
+
+
+def test_missing_command(mockexecvpe):
+    assert xexec(["-a", "foo"]) == (None, "xonsh: exec: no command specified\n", 1)
+    assert xexec(["-c"]) == (None, "xonsh: exec: no command specified\n", 1)
+    assert xexec(["-l"]) == (None, "xonsh: exec: no command specified\n", 1)
+
+
+def test_command_not_found(monkeypatch):
+
+    dummy_error_msg = "This is dummy error message, file not found or something like that"
+    command = "non_existing_command"
+
+    def mocked_execvpe(_command, _args, _env):
+        raise FileNotFoundError(2, dummy_error_msg)
+    monkeypatch.setattr(os, "execvpe", mocked_execvpe)
+
+    assert xexec([command]) == (None,
+                                "xonsh: exec: file not found: {}: {}" "\n".format(dummy_error_msg, command),
+                                1)
+
+
+def test_help(mockexecvpe):
+    assert xexec(["-h"]) == inspect.getdoc(xexec)
+    assert xexec(["--help"]) == inspect.getdoc(xexec)
+
+
+def test_a_switch(monkeypatch):
+    called = {}
+
+    def mocked_execvpe(command, args, env):
+        called.update({"command": command, "args": args, "env": env})
+
+    monkeypatch.setattr(os, "execvpe", mocked_execvpe)
+    proc_name = "foo"
+    command = "bar"
+    command_args = ["1"]
+    xexec(["-a", proc_name, command] + command_args)
+    assert called["command"] == command
+    assert called["args"][0] == proc_name
+    assert len(called["args"]) == len([command] + command_args)
+
+
+def test_l_switch(monkeypatch):
+    called = {}
+
+    def mocked_execvpe(command, args, env):
+        called.update({"command": command, "args": args, "env": env})
+
+    monkeypatch.setattr(os, "execvpe", mocked_execvpe)
+    command = "bar"
+    xexec(["-l", command, "1"])
+
+    assert called["args"][0].startswith("-")
+
+
+def test_c_switch(monkeypatch):
+    called = {}
+
+    def mocked_execvpe(command, args, env):
+        called.update({"command": command, "args": args, "env": env})
+
+    monkeypatch.setattr(os, "execvpe", mocked_execvpe)
+    command = "sleep"
+    xexec(["-c", command, "1"])
+    assert called["env"] == {}

xonsh/aliases.py

@@ -610,7 +610,7 @@ def source_cmd(args, stdin=None):
 
 
 def xexec(args, stdin=None):
-    """exec [-h|--help] command [args...]
+    """exec [-h|--help] [-cl] [-a name] command [args...]
 
     exec (also aliased as xexec) uses the os.execvpe() function to
     replace the xonsh process with the specified program. This provides
@@ -620,6 +620,13 @@ def xexec(args, stdin=None):
         bash $
 
     The '-h' and '--help' options print this message and exit.
+    If the '-l' option is supplied, the shell places a dash at the
+    beginning of the zeroth argument passed to command to simulate login
+    shell.
+    The '-c' option causes command to be executed with an empty environment.
+    If '-a' is supplied, the shell passes name as the zeroth argument
+    to the executed command.
+
 
     Notes
     -----
@@ -633,18 +640,40 @@ def xexec(args, stdin=None):
     """
     if len(args) == 0:
         return (None, "xonsh: exec: no args specified\n", 1)
-    elif args[0] == "-h" or args[0] == "--help":
+
+    parser = argparse.ArgumentParser(add_help=False)
+    parser.add_argument("-h", "--help", action="store_true")
+    parser.add_argument("-l", dest="login", action="store_true")
+    parser.add_argument("-c", dest="clean", action="store_true")
+    parser.add_argument("-a", dest="name", nargs="?")
+    parser.add_argument("command", nargs=argparse.REMAINDER)
+    args = parser.parse_args(args)
+
+    if args.help:
         return inspect.getdoc(xexec)
-    else:
+
+    if len(args.command) == 0:
+        return (None, "xonsh: exec: no command specified\n", 1)
+
+    command = args.command[0]
+    if args.name is not None:
+        args.command[0] = args.name
+    if args.login:
+        args.command[0] = "-{}".format(args.command[0])
+
+    denv = {}
+    if not args.clean:
         denv = builtins.__xonsh__.env.detype()
-        try:
-            os.execvpe(args[0], args, denv)
-        except FileNotFoundError as e:
-            return (
-                None,
-                "xonsh: exec: file not found: {}: {}" "\n".format(e.args[1], args[0]),
-                1,
-            )
+
+    try:
+        os.execvpe(command, args.command, denv)
+    except FileNotFoundError as e:
+        return (
+            None,
+            "xonsh: exec: file not found: {}: {}"
+            "\n".format(e.args[1], args.command[0]),
+            1,
+        )
 
 
 class AWitchAWitch(argparse.Action):

xonsh/main.py

@@ -292,7 +292,11 @@ def start_services(shell_kwargs, args):
     env = builtins.__xonsh__.env
     rc = shell_kwargs.get("rc", None)
     rc = env.get("XONSHRC") if rc is None else rc
-    if args.mode != XonshMode.interactive and not args.force_interactive:
+    if (
+        args.mode != XonshMode.interactive
+        and not args.force_interactive
+        and not args.login
+    ):
         #  Don't load xonshrc if not interactive shell
         rc = None
     events.on_pre_rc.fire()
@@ -329,7 +333,8 @@ def premain(argv=None):
         "cacheall": args.cacheall,
         "ctx": builtins.__xonsh__.ctx,
     }
-    if args.login:
+    if args.login or sys.argv[0].startswith("-"):
+        args.login = True
         shell_kwargs["login"] = True
     if args.norc:
         shell_kwargs["rc"] = ()