ProcessBuilder: allow unsetting of inputs through attribute deletion (

#4419)

The builder object was already able to delete set inputs through the
`__delitem__` method, but `__delattr__` was not implemented causing
`del builder.input_name` to raise. This is not consistent with how these
inputs can be set or accessed as both `__getattr__` and `__setattr__`
are implemented. Implementing `__delattr__` brings the implementation
up to par for all attribute methods.

aiida/engine/processes/builder.py

@@ -7,10 +7,10 @@
 # For further information on the license, see the LICENSE.txt file        #
 # For further information please visit http://www.aiida.net               #
 ###########################################################################
-# pylint: disable=cell-var-from-loop
 """Convenience classes to help building the input dictionaries for Processes."""
 import collections
 
+from aiida.orm import Node
 from aiida.engine.processes.ports import PortNamespace
 
 __all__ = ('ProcessBuilder', 'ProcessBuilderNamespace')
@@ -37,6 +37,10 @@ def __init__(self, port_namespace):
         self._valid_fields = []
         self._data = {}
 
+        # The name and port objects have to be passed to the defined functions as defaults for
+        # their arguments, because this way the content at the time of defining the method is
+        # saved. If they are used directly in the body, it will try to capture the value from
+        # its enclosing scope at the time of being called.
         for name, port in port_namespace.items():
 
             self._valid_fields.append(name)
@@ -48,14 +52,14 @@ def fgetter(self, name=name):
                     return self._data.get(name)
             elif port.has_default():
 
-                def fgetter(self, name=name, default=port.default):
+                def fgetter(self, name=name, default=port.default):  # pylint: disable=cell-var-from-loop
                     return self._data.get(name, default)
             else:
 
                 def fgetter(self, name=name):
                     return self._data.get(name, None)
 
-            def fsetter(self, value):
+            def fsetter(self, value, name=name):
                 self._data[name] = value
 
             fgetter.__doc__ = str(port)
@@ -112,6 +116,9 @@ def __setitem__(self, item, value):
     def __delitem__(self, item):
         self._data.__delitem__(item)
 
+    def __delattr__(self, item):
+        self._data.__delitem__(item)
+
     def _update(self, *args, **kwds):
         """Update the values of the builder namespace passing a mapping as argument or individual keyword value pairs.
 
@@ -160,8 +167,6 @@ def _prune(self, value):
         :param value: a nested mapping of port values
         :return: the same mapping but without any nested namespace that is completely empty.
         """
-        from aiida.orm import Node
-
         if isinstance(value, collections.abc.Mapping) and not isinstance(value, Node):
             result = {}
             for key, sub_value in value.items():
@@ -174,7 +179,7 @@ def _prune(self, value):
         return value
 
 
-class ProcessBuilder(ProcessBuilderNamespace):
+class ProcessBuilder(ProcessBuilderNamespace):  # pylint: disable=too-many-ancestors
     """A process builder that helps setting up the inputs for creating a new process."""
 
     def __init__(self, process_class):
@@ -188,4 +193,5 @@ def __init__(self, process_class):
 
     @property
     def process_class(self):
+        """Return the process class for which this builder is constructed."""
         return self._process_class

tests/engine/processes/test_builder.py

@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+###########################################################################
+# Copyright (c), The AiiDA team. All rights reserved.                     #
+# This file is part of the AiiDA code.                                    #
+#                                                                         #
+# The code is hosted on GitHub at https://github.com/aiidateam/aiida-core #
+# For further information on the license, see the LICENSE.txt file        #
+# For further information please visit http://www.aiida.net               #
+###########################################################################
+"""Tests for `aiida.engine.processes.builder.ProcessBuilder`."""
+import pytest
+
+from aiida.calculations.arithmetic.add import ArithmeticAddCalculation
+from aiida.engine.processes.builder import ProcessBuilder
+from aiida import orm
+
+
+def test_access_methods():
+    """Test for the access methods (setter, getter, delete).
+
+    The setters are used again after calling the delete in order to check that they still work
+    after the deletion (including the validation process).
+    """
+    node_numb = orm.Int(4)
+    node_dict = orm.Dict(dict={'value': 4})
+
+    # AS ITEMS
+    builder = ProcessBuilder(ArithmeticAddCalculation)
+
+    builder['x'] = node_numb
+    assert dict(builder) == {'metadata': {'options': {}}, 'x': node_numb}
+
+    del builder['x']
+    assert dict(builder) == {'metadata': {'options': {}}}
+
+    with pytest.raises(ValueError):
+        builder['x'] = node_dict
+
+    builder['x'] = node_numb
+    assert dict(builder) == {'metadata': {'options': {}}, 'x': node_numb}
+
+    # AS ATTRIBUTES
+    del builder
+    builder = ProcessBuilder(ArithmeticAddCalculation)
+
+    builder.x = node_numb
+    assert dict(builder) == {'metadata': {'options': {}}, 'x': node_numb}
+
+    del builder.x
+    assert dict(builder) == {'metadata': {'options': {}}}
+
+    with pytest.raises(ValueError):
+        builder.x = node_dict
+
+    builder.x = node_numb
+    assert dict(builder) == {'metadata': {'options': {}}, 'x': node_numb}