fix(common): support optional keyword-only parameters when validating…

… callables

ibis/common/patterns.py

@@ -1520,20 +1520,18 @@ def match(self, value, context):
         fn = annotated(self.args, self.return_, value)
 
         has_varargs = False
-        positional, keyword_only = [], []
+        positional = []
         for p in fn.__signature__.parameters.values():
             if p.kind in (Parameter.POSITIONAL_ONLY, Parameter.POSITIONAL_OR_KEYWORD):
                 positional.append(p)
-            elif p.kind is Parameter.KEYWORD_ONLY:
-                keyword_only.append(p)
+            elif p.kind is Parameter.KEYWORD_ONLY and p.default is Parameter.empty:
+                raise MatchError(
+                    "Callable has mandatory keyword-only arguments which cannot be specified"
+                )
             elif p.kind is Parameter.VAR_POSITIONAL:
                 has_varargs = True
 
-        if keyword_only:
-            raise MatchError(
-                "Callable has mandatory keyword-only arguments which cannot be specified"
-            )
-        elif len(positional) > len(self.args):
+        if len(positional) > len(self.args):
             # Callable has more positional arguments than expected")
             return NoMatch
         elif len(positional) < len(self.args) and not has_varargs:

ibis/common/tests/test_patterns.py

@@ -527,15 +527,18 @@ def func_with_args(a, b, *args):
     def func_with_kwargs(a, b, c=1, **kwargs):
         return str(a) + b + str(c)
 
-    def func_with_mandatory_kwargs(*, c):
+    def func_with_optional_keyword_only_kwargs(a, *, c=1):
+        return a + c
+
+    def func_with_required_keyword_only_kwargs(*, c):
         return c
 
     p = CallableWith([InstanceOf(int), InstanceOf(str)])
     assert p.match(10, context={}) is NoMatch
 
     msg = "Callable has mandatory keyword-only arguments which cannot be specified"
     with pytest.raises(MatchError, match=msg):
-        p.match(func_with_mandatory_kwargs, context={})
+        p.match(func_with_required_keyword_only_kwargs, context={})
 
     # Callable has more positional arguments than expected
     p = CallableWith([InstanceOf(int)] * 2)
@@ -556,6 +559,10 @@ def func_with_mandatory_kwargs(*, c):
     with pytest.raises(ValidationError, match="2 doesn't match InstanceOf"):
         wrapped(1, 2)
 
+    p = CallableWith([InstanceOf(int)])
+    wrapped = p.match(func_with_optional_keyword_only_kwargs, context={})
+    assert wrapped(1) == 2
+
 
 def test_pattern_list():
     p = PatternSequence([1, 2, InstanceOf(int), ...])