Issue 703 -- support for Decimal type

graphene/__init__.py

@@ -18,6 +18,7 @@
     Date,
     DateTime,
     Time,
+    Decimal,
     JSONString,
     UUID,
     List,
@@ -65,6 +66,7 @@
     "Date",
     "DateTime",
     "Time",
+    "Decimal",
     "JSONString",
     "UUID",
     "List",

graphene/types/__init__.py

@@ -6,6 +6,7 @@
 from .mutation import Mutation
 from .scalars import Scalar, String, ID, Int, Float, Boolean
 from .datetime import Date, DateTime, Time
+from .decimal import Decimal
 from .json import JSONString
 from .uuid import UUID
 from .schema import Schema
@@ -40,6 +41,7 @@
     "Date",
     "DateTime",
     "Time",
+    "Decimal",
     "JSONString",
     "UUID",
     "Boolean",

graphene/types/decimal.py

@@ -0,0 +1,34 @@
+from __future__ import absolute_import
+
+from decimal import Decimal as _Decimal
+
+from graphql.language import ast
+
+from .scalars import Scalar
+
+
+class Decimal(Scalar):
+    """
+    The `Decimal` scalar type represents a python Decimal.
+    """
+
+    @staticmethod
+    def serialize(dec):
+        if isinstance(dec, str):
+            dec = _Decimal(dec)
+        assert isinstance(dec, _Decimal), 'Received not compatible Decimal "{}"'.format(
+            repr(dec)
+        )
+        return str(dec)
+
+    @classmethod
+    def parse_literal(cls, node):
+        if isinstance(node, ast.StringValue):
+            return cls.parse_value(node.value)
+
+    @staticmethod
+    def parse_value(value):
+        try:
+            return _Decimal(value)
+        except ValueError:
+            return None

graphene/types/tests/test_decimal.py

@@ -0,0 +1,43 @@
+import decimal
+
+from ..decimal import Decimal
+from ..objecttype import ObjectType
+from ..schema import Schema
+
+
+class Query(ObjectType):
+    decimal = Decimal(input=Decimal())
+
+    def resolve_decimal(self, info, input):
+        return input
+
+
+schema = Schema(query=Query)
+
+
+def test_decimal_string_query():
+    decimal_value = decimal.Decimal("1969.1974")
+    result = schema.execute("""{ decimal(input: "%s") }""" % decimal_value)
+    assert not result.errors
+    assert result.data == {"decimal": str(decimal_value)}
+    assert decimal.Decimal(result.data["decimal"]) == decimal_value
+
+
+def test_decimal_string_query_variable():
+    decimal_value = decimal.Decimal("1969.1974")
+
+    result = schema.execute(
+        """query Test($decimal: Decimal){ decimal(input: $decimal) }""",
+        variable_values={"decimal": decimal_value},
+    )
+    assert not result.errors
+    assert result.data == {"decimal": str(decimal_value)}
+    assert decimal.Decimal(result.data["decimal"]) == decimal_value
+
+
+def test_bad_decimal_query():
+    not_a_decimal = "Nobody expects the Spanish Inquisition!"
+
+    result = schema.execute("""{ decimal(input: "%s") }""" % not_a_decimal)
+    assert len(result.errors) == 1
+    assert result.data is None