Improve argument parser

julia/pseudo_python_cli.py

@@ -99,12 +99,51 @@ def make_parser(description=__doc__):
     return parser
 
 
+def parse_args_with(parser, args):
+    ns = parser.parse_args(list(preprocess_args(args)))
+    if (ns.command or ns.module) and ns.script:
+        ns.args = [ns.script] + ns.args
+        ns.script = None
+    return ns
+
+
+def parse_args(args):
+    return parse_args_with(make_parser(), args)
+
+
+def preprocess_args(args):
+    """
+    Insert "--" after "[-c cmd | -m mod | script | -]"
+
+    This is required for the following to work:
+
+    >>> ns = parse_args(["-mjson.tool", "-h"])
+    >>> ns.args
+    ['-h']
+    """
+    it = iter(args)
+    for a in it:
+        yield a
+
+        if a in ("-m", "-c"):
+            try:
+                yield next(it)
+            except StopIteration:
+                return
+            yield "--"
+        elif a == "-":
+            yield "--"
+        elif a.startswith("-"):
+            if a[1] in ("m", "c"):
+                yield "--"
+            # otherwise, it's some
+
+
 def main(args=None):
     if args is None:
         args = sys.argv[1:]
-    parser = make_parser()
     try:
-        ns = parser.parse_args(args)
+        ns = parse_args(args)
         python(**vars(ns))
     except SystemExit as err:
         return err.code

julia/python_jl.py

@@ -28,7 +28,7 @@
 import os
 import sys
 
-from .pseudo_python_cli import make_parser
+from .pseudo_python_cli import make_parser, parse_args_with
 
 script_jl = """
 import PyCall
@@ -106,7 +106,7 @@ def parse_pyjl_args(args):
         Julia interpreter to be used.
         """)
 
-    ns = parser.parse_args(args)
+    ns = parse_args_with(parser, args)
     unused_args = list(remove_julia_options(args))
     return ns, unused_args
 

test/test_pseudo_python_cli.py

@@ -0,0 +1,45 @@
+import shlex
+
+import pytest
+
+from julia.pseudo_python_cli import parse_args
+
+
+def make_dict(**kwargs):
+    ns = parse_args([])
+    return dict(vars(ns), **kwargs)
+
+
+@pytest.mark.parametrize("args, desired", [
+    ("-m json.tool -h", make_dict(module="json.tool", args=["-h"])),
+    ("-mjson.tool -h", make_dict(module="json.tool", args=["-h"])),
+    ("-m ipykernel install --user --name NAME --display-name DISPLAY_NAME",
+     make_dict(module="ipykernel",
+               args=shlex.split("install --user --name NAME"
+                                " --display-name DISPLAY_NAME"))),
+    ("-m ipykernel_launcher -f FILE",
+     make_dict(module="ipykernel_launcher",
+               args=shlex.split("-f FILE"))),
+])
+def test_parse_args(args, desired):
+    ns = parse_args(shlex.split(args))
+    actual = vars(ns)
+    assert actual == desired
+
+
+@pytest.mark.parametrize("cli_args", [
+    ["-h"],
+    ["-i", "--help"],
+    ["-h", "-i"],
+    ["-hi"],
+    ["-ih"],
+    ["-h", "-m", "json.tool"],
+    ["-h", "-mjson.tool"],
+])
+def test_help_option(cli_args, capsys):
+    with pytest.raises(SystemExit) as exc_info:
+        parse_args(cli_args)
+    assert exc_info.value.code == 0
+
+    captured = capsys.readouterr()
+    assert "usage:" in captured.out