add error handling for argparse's choices

rest_tools/server/arghandler.py

@@ -1,4 +1,4 @@
-"""Handle argument parsing, defaulting, and casting."""
+"""Handle argument parsing, defaulting, casting, and more."""
 
 
 import argparse
@@ -10,33 +10,49 @@
 import sys
 import time
 import traceback
-from typing import Any, List, TypeVar, Union, cast
+from typing import Any, List, Union, cast
 
 import tornado.web
 from tornado.escape import to_unicode
 from wipac_dev_tools import strtobool
 
 from .handler import RestHandler
 
-T = TypeVar("T")
-
 LOGGER = logging.getLogger(__name__)
 
 
+###############################################################################
+# Constants
+
+USE_CACHED_VALUE_PLACEHOLDER = "PLACEHOLDER"
+
+
 class ArgumentSource(enum.Enum):
     """For mapping to argument sources."""
 
     QUERY_ARGUMENTS = enum.auto()
     JSON_BODY_ARGUMENTS = enum.auto()
 
 
+###############################################################################
+# Error Patterns
+
+# __main__.py: error: the following arguments are required: --reqd, --bar
 ARGUMENTS_REQUIRED_PATTERN = re.compile(
     r".+: error: (the following arguments are required: .+)"
 )
+
+# __main__.py: error: unrecognized arguments: --xtra 1 --another True False who knows
 UNRECOGNIZED_ARGUMENTS_PATTERN = re.compile(r".+ error: (unrecognized arguments:) (.+)")
+
+# argument --foo: invalid int value: 'hank'
 INVALID_VALUE_PATTERN = re.compile(r"(argument .+: invalid) .+ value: '.+'")
 
-USE_CACHED_VALUE_PLACEHOLDER = "PLACEHOLDER"
+# argument --pick_it: invalid choice: 'hammer' (choose from 'rock', 'paper', 'scissors')
+INVALID_CHOICE_PATTERN = re.compile(r"(argument .+: invalid choice: .+)")
+
+
+###############################################################################
 
 
 class ArgumentHandler:
@@ -152,11 +168,15 @@ def _translate_error(
                 return f"{match.group(1)} {', '.join(args)}"
 
         # INVALID VALUE -- not a system error bc 'exit_on_error=False' (in __init__)
-        # ex:
-        #   argument --foo: invalid int value: 'hank'
         elif isinstance(exc, argparse.ArgumentError):
+            # ex:
+            #   argument --foo: invalid int value: 'hank'
             if match := INVALID_VALUE_PATTERN.search(str(exc)):
                 return f"{match.group(1).replace('--', '')} type"
+            # ex:
+            #   argument --pick_it: invalid choice: 'hammer' (choose from 'rock', 'paper', 'scissors')
+            elif match := INVALID_CHOICE_PATTERN.search(str(exc)):
+                return match.group(1).replace("--", "")
 
         # FALL-THROUGH -- log unknown exception
         ts = time.time()  # log timestamp to aid debugging

tests/unit_server/arghandler_test.py

@@ -471,6 +471,48 @@ def test_210__argparse_choices(argument_source: str) -> None:
         assert val == getattr(outargs, arg.replace("-", "_"))
 
 
+@pytest.mark.parametrize(
+    "argument_source",
+    [QUERY_ARGUMENTS, JSON_BODY_ARGUMENTS],
+)
+def test_211__argparse_choices__error(argument_source: str) -> None:
+    """Test `argument_source` arguments using argparse's advanced options."""
+    args: Dict[str, Any] = {
+        "pick_it": "paper",
+        "bar": "True",
+    }
+    choices: List = ["rock", "paper", "scissors"]
+    if argument_source == JSON_BODY_ARGUMENTS:
+        args.update(
+            {
+                "pick_it": {"abc": 123},
+                "listo": [1, 2, 3],
+            }
+        )
+        choices = [{"abc": 123}, {"def": 456}, {"ghi": 789}]
+
+    # set up ArgumentHandler
+    arghand = setup_argument_handler(
+        argument_source,
+        {k: v if k != "pick_it" else "hank" for k, v in args.items()},
+    )
+
+    for arg, _ in args.items():
+        print()
+        print(arg)
+        if arg == "pick_it":
+            arghand.add_argument(arg, choices=choices)
+        else:
+            arghand.add_argument(arg)
+
+    with pytest.raises(tornado.web.HTTPError) as e:
+        arghand.parse_args()
+    assert (
+        str(e.value)
+        == f"HTTP 400: argument pick_it: invalid choice: 'hank' (choose from {', '.join(repr(c) for c in choices)})"
+    )
+
+
 @pytest.mark.parametrize(
     "argument_source",
     [QUERY_ARGUMENTS, JSON_BODY_ARGUMENTS],