Add tests and refine approach.

scabha/basetypes.py

@@ -1,11 +1,15 @@
+from __future__ import annotations
 from dataclasses import field, dataclass
 from collections import OrderedDict
-from typing import List, Union, get_args, get_origin
+from typing import List, Union, get_args, get_origin, Any
 import os.path
 import re
 from .exceptions import UnsetError
 from itertools import zip_longest
-from typeguard import check_type, TypeCheckError
+from typeguard import (
+    check_type, TypeCheckError, TypeCheckerCallable, TypeCheckMemo, checker_lookup_functions
+)
+from inspect import isclass
 
 
 def EmptyDictDefault():
@@ -118,11 +122,21 @@ def is_file_list_type(dtype):
     return any(dtype == List[t] for t in FILE_TYPES)
 
 
-class Skip(object):
-    def iterate_samples(self, collection):
-        return ()
+def check_filelike(value: Any, origin_type: Any, args: tuple[Any, ...], memo: TypeCheckMemo) -> None:
+    """Custom checker for filelike objects. Currently checks for strings."""
+    if not isinstance(value, str):
+        raise TypeCheckError(f'{value} is not compatible with URI or its subclasses.')
 
 
+def filelike_lookup(origin_type: Any, args: tuple[Any, ...], extras: tuple[Any, ...]) -> TypeCheckerCallable | None:
+    """Lookup the custom checker for filelike objects."""
+    if isclass(origin_type) and issubclass(origin_type, URI):
+        return check_filelike
+
+    return None
+
+checker_lookup_functions.append(filelike_lookup)  # Register custom type checker.
+
 def get_filelikes(dtype, value, filelikes=None):
     """Recursively recover all filelike elements from a composite dtype."""
 
@@ -152,21 +166,19 @@ def get_filelikes(dtype, value, filelikes=None):
                 return filelikes
 
             # This is a special case for tuples of arbitrary
-            # length i.e. list-like behaviour.
-            if ... in args:
-                args = tuple([a for a in args if a != ...])
+            # length i.e. list-like behaviour. We can simply 
+            # strip out the Ellipsis.
+            args = tuple([arg for arg in args if arg != ...])
 
             for dt, v in zip_longest(args, value, fillvalue=args[0]):
                 filelikes = get_filelikes(dt, v, filelikes)
 
         elif origin is Union:
 
             for dt in args:
-
                 try:
-                    # Do not check collection member types. 
-                    check_type(value, dt, collection_check_strategy=Skip())
-                except TypeCheckError:
+                    check_type(value, dt)
+                except TypeCheckError:  # Value doesn't match dtype - incorrect branch.
                     continue
                 filelikes = get_filelikes(dt, value, filelikes)
 

tests/scabha_tests/test_filelikes.py

@@ -0,0 +1,42 @@
+from scabha.basetypes import get_filelikes, File, URI, Directory, MS
+from typing import Dict, List, Set, Tuple, Union, Optional
+import pytest
+
+
+@pytest.fixture(scope="module", params=[File, URI, Directory, MS])
+def templates(request):
+
+    ft = request.param
+
+    TEMPLATES = (
+        (Tuple, (), set()),
+        (Tuple[int, ...], [1, 2], set()),
+        (Tuple[ft, ...], ("foo", "bar"), {"foo", "bar"}),
+        (Tuple[ft, str], ("foo", "bar"), {"foo"}),
+        (Dict[str, int], {"a": 1, "b": 2}, set()),
+        (Dict[str, ft], {"a": "foo", "b": "bar"}, {"foo", "bar"}),
+        (Dict[ft, str], {"foo": "a", "bar": "b"}, {"foo", "bar"}),
+        (List[ft], [], set()),
+        (List[int], [1, 2], set()),
+        (List[ft], ["foo", "bar"], {"foo", "bar"}),
+        (Set[ft], set(), set()),
+        (Set[int], {1, 2}, set()),
+        (Set[ft], {"foo", "bar"}, {"foo", "bar"}),
+        (Union[str, List[ft]], "foo", set()),
+        (Union[str, List[ft]], ["foo"], {"foo"}),
+        (Union[str, Tuple[ft]], "foo", set()),
+        (Union[str, Tuple[ft]], ("foo",), {"foo"}),
+        (Optional[ft], None, set()),
+        (Optional[ft], "foo", {"foo"}),
+        (Optional[Union[ft, int]], 1, set()),
+        (Optional[Union[ft, int]], "foo", {"foo"}),
+        (Dict[str, Tuple[ft, str]], {"a": ("foo", "bar")}, {"foo"})
+    )
+
+    return TEMPLATES
+
+
+def test_get_filelikes(templates):
+
+    for dt, v, res in templates:
+        assert get_filelikes(dt, v) == res, f"Failed for dtype {dt} and value {v}."