From 1b7b4c81444b049f235e6197f0b38086139c2296 Mon Sep 17 00:00:00 2001
From: Dorota Jarecka <djarecka@gmail.com>
Date: Sun, 20 Sep 2020 22:49:29 -0400
Subject: [PATCH] improving syntax for input/output_spec

---
 pydra/engine/task.py | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/pydra/engine/task.py b/pydra/engine/task.py
index ace102c029..1d17b577f7 100644
--- a/pydra/engine/task.py
+++ b/pydra/engine/task.py
@@ -217,6 +217,9 @@ def _run_task(self):
 class ShellCommandTask(TaskBase):
     """Wrap a shell command as a task element."""
 
+    input_spec = None
+    output_spec = None
+
     def __new__(cls, container_info=None, *args, **kwargs):
         if not container_info:
             return super().__new__(cls)
@@ -276,21 +279,18 @@ def __init__(
             TODO
 
         """
-        if input_spec is not None:
-            self.input_spec = input_spec
-        elif not hasattr(self, "input_spec"):
-            self.input_spec = SpecInfo(name="Inputs", fields=[], bases=(ShellSpec,))
-        else:
-            # changing class attribute to instance attribute, so it is part of __dict__
-            # (used in TaskBase.__set/get-state__)
-            self.input_spec = self.input_spec
-        if output_spec is not None:
-            self.output_spec = output_spec
-        elif not hasattr(self, "output_spec"):
-            self.output_spec = SpecInfo(name="Output", fields=[], bases=(ShellOutSpec,))
-        else:
-            # changing class attribute to instance attribute, so it is part of __dict__
-            self.output_spec = self.output_spec
+
+        # using provided spec, class attribute or setting the default SpecInfo
+        self.input_spec = (
+            input_spec
+            or self.input_spec
+            or SpecInfo(name="Inputs", fields=[], bases=(ShellSpec,))
+        )
+        self.output_spec = (
+            output_spec
+            or self.output_spec
+            or SpecInfo(name="Output", fields=[], bases=(ShellOutSpec,))
+        )
         self.output_spec = output_from_inputfields(self.output_spec, self.input_spec)
 
         for special_inp in ["executable", "args"]: