Merge pull request #632 from ghisvail/fix/specs/staticmethod-as-callable

FIX: Allow staticmethod be passed to callable metadata in ouput spec

Author: ghisvail

pydra/engine/specs.py

@@ -602,7 +602,12 @@ def _field_metadata(
                     return attr.NOTHING
                 return val
         elif "callable" in fld.metadata:
-            call_args = inspect.getfullargspec(fld.metadata["callable"])
+            callable_ = fld.metadata["callable"]
+            if isinstance(callable_, staticmethod):
+                # In case callable is defined as a static method,
+                # retrieve the function wrapped in the descriptor.
+                callable_ = callable_.__func__
+            call_args = inspect.getfullargspec(callable_)
             call_args_val = {}
             for argnm in call_args.args:
                 if argnm == "field":
@@ -624,7 +629,7 @@ def _field_metadata(
                             f"has to be in inputs or be field or output_dir, "
                             f"but {argnm} is used"
                         )
-            return fld.metadata["callable"](**call_args_val)
+            return callable_(**call_args_val)
         else:
             raise Exception("(_field_metadata) is not a current valid metadata key.")
 

pydra/engine/tests/test_shelltask.py

@@ -2928,6 +2928,35 @@ def gather_output(executable, output_dir, ble):
         shelly()
 
 
+@pytest.mark.parametrize("results_function", [result_no_submitter, result_submitter])
+def test_shell_cmd_outputspec_5c(plugin, results_function):
+    """
+    Customised output spec defined as a class,
+    using a static function to collect output files.
+    """
+
+    @attr.s(kw_only=True)
+    class MyOutputSpec(ShellOutSpec):
+        @staticmethod
+        def gather_output(executable, output_dir):
+            files = executable[1:]
+            return [Path(output_dir) / file for file in files]
+
+        newfile: MultiOutputFile = attr.ib(metadata={"callable": gather_output})
+
+    shelly = ShellCommandTask(
+        name="shelly",
+        executable=["touch", "newfile_tmp1.txt", "newfile_tmp2.txt"],
+        output_spec=SpecInfo(name="Output", bases=(MyOutputSpec,)),
+    )
+
+    res = results_function(shelly, plugin)
+    assert res.output.stdout == ""
+    # newfile is a list
+    assert len(res.output.newfile) == 2
+    assert all([file.exists for file in res.output.newfile])
+
+
 @pytest.mark.parametrize("results_function", [result_no_submitter, result_submitter])
 def test_shell_cmd_outputspec_6(plugin, results_function, tmpdir):
     """