Add support to pass args/kwargs to callables from Accessor (#940)

Fixes: #939

django_tables2/utils.py

@@ -303,7 +303,12 @@ class Accessor(str):
         "Failed lookup for key [{key}] in {context}, when resolving the accessor {accessor}"
     )
 
-    def __new__(cls, value):
+    def __init__(self, value, callable_args=None, callable_kwargs=None):
+        self.callable_args = callable_args or getattr(value, "callable_args", None) or []
+        self.callable_kwargs = callable_kwargs or getattr(value, "callable_kwargs", None) or {}
+        super().__init__()
+
+    def __new__(cls, value, callable_args=None, callable_kwargs=None):
         instance = super().__new__(cls, value)
         if cls.LEGACY_SEPARATOR in value:
             instance.SEPARATOR = cls.LEGACY_SEPARATOR
@@ -394,7 +399,7 @@ def resolve(self, context, safe=True, quiet=False):
                     if safe and getattr(current, "alters_data", False):
                         raise ValueError(self.ALTERS_DATA_ERROR_FMT.format(method=current.__name__))
                     if not getattr(current, "do_not_call_in_templates", False):
-                        current = current()
+                        current = current(*self.callable_args, **self.callable_kwargs)
                 # Important that we break in None case, or a relationship
                 # spanning across a null-key will raise an exception in the
                 # next iteration, instead of defaulting.

tests/test_utils.py

@@ -130,6 +130,17 @@ def test_short_circuit_dict(self):
 
         self.assertEqual(Accessor("occupation__name").resolve(context), "Carpenter")
 
+    def test_callable_args_kwargs(self):
+        class MyClass:
+            def method(self, *args, **kwargs):
+                return args, kwargs
+
+        callable_args = ("arg1", "arg2")
+        callable_kwargs = {"kwarg1": "val1", "kwarg2": "val2"}
+        obj = MyClass()
+        result = Accessor("method", callable_args, callable_kwargs).resolve(obj)
+        self.assertEqual(result, (callable_args, callable_kwargs))
+
 
 class AccessorTestModel(models.Model):
     foo = models.CharField(max_length=20)