Implement nullvalue

graphql/language/ast.py

@@ -534,6 +534,32 @@ def __hash__(self):
         return id(self)
 
 
+class NullValue(Value):
+    __slots__ = ('loc', 'value')
+    _fields = ('value',)
+
+    def __init__(self, value=None, loc=None):
+        self.loc = loc
+        self.value = value
+
+    def __eq__(self, other):
+        return isinstance(other, NullValue)
+
+    def __repr__(self):
+        return ('NullValue('
+                'value={self.value!r}'
+                ')').format(self=self)
+
+    def __copy__(self):
+        return type(self)(
+            self.value,
+            self.loc
+        )
+
+    def __hash__(self):
+        return id(self)
+
+
 class EnumValue(Value):
     __slots__ = ('loc', 'value',)
     _fields = ('value',)

graphql/language/parser.py

@@ -418,7 +418,11 @@ def parse_value_literal(parser, is_const):
             advance(parser)
             return ast.BooleanValue(value=token.value == 'true', loc=loc(parser, token.start))
 
-        if token.value != 'null':
+        elif token.value in ('null', ):
+            advance(parser)
+            return ast.NullValue(loc=loc(parser, token.start))
+
+        else:
             advance(parser)
             return ast.EnumValue(value=token.value, loc=loc(parser, token.start))
 

graphql/language/printer.py

@@ -81,6 +81,9 @@ def leave_StringValue(self, node, *args):
     def leave_BooleanValue(self, node, *args):
         return json.dumps(node.value)
 
+    def leave_NullValue(self, node, *args):
+        return json.dumps(node.value)
+
     def leave_EnumValue(self, node, *args):
         return node.value
 

graphql/language/tests/fixtures.py

@@ -53,7 +53,7 @@
 }
 
 {
-  unnamed(truthy: true, falsey: false),
+  unnamed(truthy: true, falsey: false, nullish: null),
   query
 }
 """

graphql/language/tests/test_parser.py

@@ -77,13 +77,6 @@ def test_does_not_accept_fragments_spread_of_on():
     assert 'Syntax Error GraphQL (1:9) Expected Name, found }' in excinfo.value.message
 
 
-def test_does_not_allow_null_value():
-    with raises(GraphQLSyntaxError) as excinfo:
-        parse('{ fieldWithNullableStringInput(input: null) }')
-
-    assert 'Syntax Error GraphQL (1:39) Unexpected Name "null"' in excinfo.value.message
-
-
 def test_parses_multi_byte_characters():
     result = parse(u'''
         # This comment has a \u0A0A multi-byte character.

graphql/language/tests/test_printer.py

@@ -118,7 +118,7 @@ def test_prints_kitchen_sink():
 }
 
 {
-  unnamed(truthy: true, falsey: false)
+  unnamed(truthy: true, falsey: false, nullish: null)
   query
 }
 '''

graphql/language/tests/test_visitor.py

@@ -562,6 +562,12 @@ def leave(self, node, key, parent, *args):
         ['enter', 'BooleanValue', 'value', 'Argument'],
         ['leave', 'BooleanValue', 'value', 'Argument'],
         ['leave', 'Argument', 1, None],
+        ['enter', 'Argument', 2, None],
+        ['enter', 'Name', 'name', 'Argument'],
+        ['leave', 'Name', 'name', 'Argument'],
+        ['enter', 'NullValue', 'value', 'Argument'],
+        ['leave', 'NullValue', 'value', 'Argument'],
+        ['leave', 'Argument', 2, None],
         ['leave', 'Field', 0, None],
         ['enter', 'Field', 1, None],
         ['enter', 'Name', 'name', 'Field'],

graphql/language/visitor_meta.py

@@ -19,6 +19,7 @@
     ast.FloatValue: (),
     ast.StringValue: (),
     ast.BooleanValue: (),
+    ast.NullValue: (),
     ast.EnumValue: (),
     ast.ListValue: ('values',),
     ast.ObjectValue: ('fields',),