systemfields: allow omitting key name in field

* Adds possibility to not add a key name and instead use the attribute
  name as default.

invenio_records/systemfields/base.py

@@ -63,7 +63,7 @@ class SystemField(ExtensionMixin):
 
     def __init__(self, key=None):
         """Initialise the field."""
-        self.key = key
+        self._key = key
         # The attribute is set by __set_name__ which is called by the metaclass
         # during construction.
         self._attr_name = None
@@ -77,6 +77,14 @@ def attr_name(self):
         """
         return self._attr_name
 
+    @property
+    def key(self):
+        """Property to access the dict key name.
+
+        Uses the attribute name if the key is not defined.
+        """
+        return self._key or self._attr_name
+
     #
     # Data descriptor definition
     #

invenio_records/systemfields/constant.py

@@ -15,15 +15,15 @@
 class ConstantField(SystemField):
     """Constant fields add a constant value to a key in the record."""
 
-    def __init__(self, key, value):
+    def __init__(self, key=None, value=''):
         """Initialize the field.
 
         :param key: The key to set in the dictionary (dot notation supported
                     for nested lookup).
         :param value: The value to set for the key.
         """
-        self.key = key
         self.value = value
+        super().__init__(key=key)
 
     def pre_init(self, record, data, model=None, **kwargs):
         """Sets the key in the record during record instantiation."""

invenio_records/systemfields/dict.py

@@ -19,7 +19,7 @@ class DictField(SystemField):
     Provides a shortcut for getting/setting a specific key on a record.
     """
 
-    def __init__(self, key, clear_none=False, create_if_missing=True):
+    def __init__(self, key=None, clear_none=False, create_if_missing=True):
         """Initialise the dict field.
 
         :param key: Key to set (dot notation supported).

tests/test_systemfields.py

@@ -293,6 +293,14 @@ class TestRecord(Record, SystemFieldsMixin):
     assert record['arg_value'] == 'testval'
 
 
+def test_default_key(testapp):
+    """Test default key name."""
+    class TestRecord(Record, SystemFieldsMixin):
+        afield = ConstantField(value='test')
+
+    assert TestRecord({})['afield'] == 'test'
+
+
 #
 # DictField
 #
@@ -316,6 +324,14 @@ class Record1(Record, SystemFieldsMixin):
         metadata={'title': 1}) == {'metadata': {'title': 1}, 'a': 'b'}
 
 
+def test_dictfield_default_key(testapp):
+    """Test default key name."""
+    class TestRecord(Record, SystemFieldsMixin):
+        afield = DictField()
+
+    assert TestRecord({}, afield={'test': 1})['afield'] == {'test': 1}
+
+
 def test_dict_field_complex_key():
     """More complex tests for the DictField."""
     class Record1(Record, SystemFieldsMixin):