feat: allow construction of decimal literals

ibis/expr/datatypes.py

@@ -4,6 +4,7 @@
 import builtins
 import collections
 import datetime
+import decimal
 import enum
 import functools
 import itertools
@@ -1571,3 +1572,8 @@ def _str_to_uuid(typ: UUID, value: str) -> _uuid.UUID:
 @_normalize.register(String, _uuid.UUID)
 def _uuid_to_str(typ: String, value: _uuid.UUID) -> str:
     return str(value)
+
+
+@_normalize.register(Decimal, int)
+def _int_to_decimal(typ: Decimal, value: int) -> decimal.Decimal:
+    return decimal.Decimal(value).scaleb(-typ.scale)

ibis/expr/operations/generic.py

@@ -1,4 +1,5 @@
 import datetime
+import decimal
 import enum
 import functools
 import itertools
@@ -242,6 +243,7 @@ class Literal(ValueOp):
                     tuple,
                     type(None),
                     uuid.UUID,
+                    decimal.Decimal,
                 )
             ),
             rlz.is_computable_input,

ibis/tests/expr/test_value_exprs.py

@@ -4,6 +4,7 @@
 import uuid
 from collections import OrderedDict
 from datetime import date, datetime, time
+from decimal import Decimal
 from operator import methodcaller
 
 import numpy as np
@@ -112,13 +113,34 @@ def test_literal_with_implicit_type(value, expected_type):
         (tuple(multipolygon1), 'multipolygon'),
         pytest.param(uuid.uuid4(), 'uuid', id='uuid'),
         pytest.param(str(uuid.uuid4()), 'uuid', id='uuid_str'),
+        pytest.param(Decimal("234.234"), "decimal(6, 3)", id="decimal_native"),
+        pytest.param(234234, "decimal(6, 3)", id="decimal_int"),
     ],
 )
 def test_literal_with_explicit_type(value, expected_type):
     expr = ibis.literal(value, type=expected_type)
     assert expr.type().equals(dt.validate_type(expected_type))
 
 
+@pytest.mark.parametrize(
+    ("value", "expected", "dtype"),
+    [
+        # precision > scale
+        (Decimal("234.234"), Decimal("234.234"), "decimal(6, 3)"),
+        (234234, Decimal("234.234"), "decimal(6, 3)"),
+        # scale == 0
+        (Decimal("234"), Decimal("234"), "decimal(6, 0)"),
+        (234, Decimal("234"), "decimal(6, 0)"),
+        # precision == scale
+        (Decimal(".234"), Decimal(".234"), "decimal(3, 3)"),
+        (234, Decimal(".234"), "decimal(3, 3)"),
+    ],
+)
+def test_normalize_decimal_literal(value, expected, dtype):
+    expr = ibis.literal(value, type=dtype)
+    assert expr.op().value == expected
+
+
 @pytest.mark.parametrize(
     ['value', 'expected_type', 'expected_class'],
     [