Removing option that input to kernel is an object

Author: erikvansebille

src/parcels/_core/kernel.py

@@ -65,9 +65,7 @@ def __init__(
             raise ValueError(f"kernels must be a list. Got {kernels=!r}")
 
         for f in kernels:
-            if isinstance(f, Kernel):
-                f = f._kernels  # unwrap
-            elif not isinstance(f, types.FunctionType):
+            if not isinstance(f, types.FunctionType):
                 raise TypeError(f"Argument `kernels` should be a function or list of functions. Got {type(f)}")
             assert_same_function_signature(f, ref=AdvectionRK4, context="Kernel")
 

src/parcels/_core/particleset.py

@@ -395,12 +395,9 @@ def execute(
         if len(self) == 0:
             return
 
-        if isinstance(kernels, Kernel):
-            self._kernel = kernels
-        else:
-            if isinstance(kernels, types.FunctionType):
-                kernels = [kernels]
-            self._kernel = Kernel(kernels, self)
+        if isinstance(kernels, types.FunctionType):
+            kernels = [kernels]
+        self._kernel = Kernel(kernels, self)
 
         if output_file is not None:
             output_file.set_metadata(self.fieldset.gridset[0]._mesh)

tests/test_kernel.py

@@ -81,7 +81,7 @@ def test_kernel_from_list_error_checking(fieldset):
     with pytest.raises(TypeError, match=r"Argument `kernels` should be a function or list of functions.*"):
         Kernel(kernels=[AdvectionRK4, "something else"], pset=pset)
 
-    with pytest.raises(TypeError, match=r".*is not a callable object"):
+    with pytest.raises(TypeError, match=r".* should be a function or list of functions.*"):
         kernels_mixed = Kernel(kernels=[Kernel(kernels=[AdvectionRK4], pset=pset), MoveEast, MoveNorth], pset=pset)
         assert kernels_mixed.funcname == "AdvectionRK4MoveEastMoveNorth"