add description/tests for empty *args

Author: alipatti

plan.md

@@ -60,6 +60,14 @@ This feature will not disrupt explicitly declared flags/options.
 ./command.py --flag input.txt --option val --unknown val2 -- arg1 arg2
 ```
 
+Empty args are handled gracefully.
+
+```bash
+# both of the following produce args = ()
+./command.py input.txt
+./command.py input.txt --
+```
+
 Unknown options *must* have values.
 (To emulate a boolean flag, simply pass a value so that `kwargs.get("unknown_flag")` is truthy.)
 

tests/test_kwargs.py

@@ -202,3 +202,21 @@ def cmd(*args: str, option: str = "default") -> None:
     result = runner.invoke(app, ["--option", "custom", "a", "b"])
     assert result.exit_code == 0, result.output
     assert json.loads(result.output.strip()) == {"args": ["a", "b"], "option": "custom"}
+
+
+def test_empty_args_without_separator() -> None:
+    """./command.py input.txt  →  args = ()"""
+    _kitchen_sink_helper(
+        ["input.txt"],
+        expected_filepath="input.txt",
+        expected_args=[],
+    )
+
+
+def test_empty_args_with_separator() -> None:
+    """./command.py input.txt --  →  args = ()"""
+    _kitchen_sink_helper(
+        ["input.txt", "--"],
+        expected_filepath="input.txt",
+        expected_args=[],
+    )