orm: permit Decimal in attributes

aiida/common/hashing.py

@@ -19,6 +19,7 @@
 from functools import singledispatch
 from itertools import chain
 from operator import itemgetter
+from decimal import Decimal
 
 import pytz
 
@@ -222,11 +223,24 @@ def _(mapping, **kwargs):
 def _(val, **kwargs):
     """
     Before hashing a float, convert to a string (via rounding) and with a fixed number of digits after the comma.
-    Note that the `_singe_digest` requires a bytes object so we need to encode the utf-8 string first
+    Note that the `_single_digest` requires a bytes object so we need to encode the utf-8 string first
     """
     return [_single_digest('float', float_to_text(val, sig=AIIDA_FLOAT_PRECISION).encode('utf-8'))]
 
 
+@_make_hash.register(Decimal)
+def _(val, **kwargs):
+    """
+    While a decimal can be converted exactly to a string which captures all characteristics of the underlying
+    implementation, we also need compatibility with "equal" representations as int or float. Hence we are checking
+    for the exponent (which is negative if there is a fractional component, 0 otherwise) and get the same hash
+    as for a corresponding float or int.
+    """
+    if val.as_tuple().exponent < 0:
+        return [_single_digest('float', float_to_text(val, sig=AIIDA_FLOAT_PRECISION).encode('utf-8'))]
+    return [_single_digest('int', f'{val}'.encode('utf-8'))]
+
+
 @_make_hash.register(numbers.Complex)
 def _(val, **kwargs):
     """

aiida/orm/implementation/utils.py

@@ -10,6 +10,7 @@
 """Utility methods for backend non-specific implementations."""
 import math
 import numbers
+from decimal import Decimal
 
 from collections.abc import Iterable, Mapping
 
@@ -63,7 +64,7 @@ def clean_builtin(val):
         It mainly checks that we don't store NaN or Inf.
         """
         # This is a whitelist of all the things we understand currently
-        if val is None or isinstance(val, (bool, str)):
+        if val is None or isinstance(val, (bool, str, Decimal)):
             return val
 
         # This fixes #2773 - in python3, ``numpy.int64(-1)`` cannot be json-serialized

tests/common/test_hashing.py

@@ -16,6 +16,7 @@
 from datetime import datetime
 import hashlib
 import uuid
+from decimal import Decimal
 
 import numpy as np
 import pytz
@@ -175,6 +176,18 @@ def test_numpy_types(self):
         )  # pylint: disable=no-member
         self.assertEqual(make_hash(np.int64(42)), '9468692328de958d7a8039e8a2eb05cd6888b7911bbc3794d0dfebd8df3482cd')  # pylint: disable=no-member
 
+    def test_decimal(self):
+        self.assertEqual(
+            make_hash(Decimal('3.141')), 'b3302aad550413e14fe44d5ead10b3aeda9884055fca77f9368c48517916d4be'
+        )  # pylint: disable=no-member
+
+        # make sure we get the same hashes as for corresponding float or int
+        self.assertEqual(make_hash(Decimal('3.141')), make_hash(3.141))  # pylint: disable=no-member
+
+        self.assertEqual(make_hash(Decimal('3.')), make_hash(3))  # pylint: disable=no-member
+
+        self.assertEqual(make_hash(Decimal('3141')), make_hash(3141))  # pylint: disable=no-member
+
     def test_unhashable_type(self):
 
         class MadeupClass:

tests/orm/node/test_node.py

@@ -12,6 +12,7 @@
 import logging
 import os
 import tempfile
+from decimal import Decimal
 
 import pytest
 
@@ -416,6 +417,13 @@ def test_extras_keys(self):
         self.node.set_extra_many(extras)
         assert set(self.node.extras_keys()) == set(extras)
 
+    def test_attribute_decimal(self):
+        """Test that the `Node.set_attribute` method supports Decimal."""
+        self.node.set_attribute('a_val', Decimal('3.141'))
+        self.node.store()
+        # ensure the returned node is a float
+        assert self.node.get_attribute('a_val') == 3.141
+
 
 @pytest.mark.usefixtures('clear_database_before_test_class')
 class TestNodeLinks: