[RFC] Allow directives on variable definitions

Replicates graphql/graphql-js@1d7efa9

Author: Cito

README.md

@@ -13,7 +13,7 @@ a query language for APIs created by Facebook.
 
 The current version 1.0.0rc2 of GraphQL-core-next is up-to-date with GraphQL.js
 version 14.0.0rc2. All parts of the API are covered by an extensive test
-suite of currently 1547 unit tests.
+suite of currently 1549 unit tests.
 
 
 ## Documentation

graphql/language/ast.py

@@ -159,11 +159,12 @@ class OperationDefinitionNode(ExecutableDefinitionNode):
 
 
 class VariableDefinitionNode(Node):
-    __slots__ = 'variable', 'type', 'default_value'
+    __slots__ = 'variable', 'type', 'default_value', 'directives'
 
     variable: 'VariableNode'
     type: 'TypeNode'
     default_value: Optional['ValueNode']
+    directives: Optional[List['DirectiveNode']]
 
 
 class SelectionSetNode(Node):

graphql/language/directive_locations.py

@@ -13,6 +13,7 @@ class DirectiveLocation(Enum):
     FIELD = 'field'
     FRAGMENT_DEFINITION = 'fragment definition'
     FRAGMENT_SPREAD = 'fragment spread'
+    VARIABLE_DEFINITION = 'variable definition'
     INLINE_FRAGMENT = 'inline fragment'
 
     # Type System Definitions

graphql/language/parser.py

@@ -169,13 +169,14 @@ def parse_variable_definitions(lexer: Lexer) -> List[VariableDefinitionNode]:
 
 
 def parse_variable_definition(lexer: Lexer) -> VariableDefinitionNode:
-    """VariableDefinition: Variable: Type DefaultValue?"""
+    """VariableDefinition: Variable: Type DefaultValue? Directives[Const]?"""
     start = lexer.token
     return VariableDefinitionNode(
         variable=parse_variable(lexer),
         type=expect(lexer, TokenKind.COLON) and parse_type_reference(lexer),
         default_value=parse_value_literal(lexer, True)
         if skip(lexer, TokenKind.EQUALS) else None,
+        directives=parse_directives(lexer, True),
         loc=loc(lexer, start))
 
 

graphql/language/printer.py

@@ -50,7 +50,9 @@ def leave_operation_definition(self, node, *_args):
         ) else selection_set
 
     def leave_variable_definition(self, node, *_args):
-        return f"{node.variable}: {node.type}{wrap(' = ', node.default_value)}"
+        return (f"{node.variable}: {node.type}"
+                f"{wrap(' = ', node.default_value)}"
+                f"{wrap(' ', ' '.join(node.directives))}")
 
     def leave_selection_set(self, node, *_args):
         return block(node.selections)

graphql/language/visitor.py

@@ -27,7 +27,7 @@
     'document': ('definitions',),
     'operation_definition': (
         'name', 'variable_definitions', 'directives', 'selection_set'),
-    'variable_definition': ('variable', 'type', 'default_value'),
+    'variable_definition': ('variable', 'type', 'default_value', 'directives'),
     'variable': ('name',),
     'selection_set': ('selections',),
     'field': ('alias', 'name', 'arguments', 'directives', 'selection_set'),

graphql/type/introspection.py

@@ -106,6 +106,9 @@ def print_value(value: Any, type_: GraphQLInputType) -> str:
         'INLINE_FRAGMENT': GraphQLEnumValue(
             DirectiveLocation.INLINE_FRAGMENT,
             description='Location adjacent to an inline fragment.'),
+        'VARIABLE_DEFINITION': GraphQLEnumValue(
+            DirectiveLocation.VARIABLE_DEFINITION,
+            description='Location adjacent to a variable definition.'),
         'SCHEMA': GraphQLEnumValue(
             DirectiveLocation.SCHEMA,
             description='Location adjacent to a schema definition.'),

graphql/validation/rules/known_directives.py

@@ -69,6 +69,7 @@ def enter_directive(
     'fragment_spread': DirectiveLocation.FRAGMENT_SPREAD,
     'inline_fragment': DirectiveLocation.INLINE_FRAGMENT,
     'fragment_definition': DirectiveLocation.FRAGMENT_DEFINITION,
+    'variable_definition': DirectiveLocation.VARIABLE_DEFINITION,
     'schema_definition': DirectiveLocation.SCHEMA,
     'schema_extension': DirectiveLocation.SCHEMA,
     'scalar_type_definition': DirectiveLocation.SCALAR,

tests/language/test_parser.py

@@ -82,6 +82,9 @@ def parses_constant_default_values():
           'query Foo($x: Complex = { a: { b: [ $var ] } }) { field }',
           'Unexpected $', (1, 37))
 
+    def parses_variable_definition_directives():
+        parse('query Foo($x: Boolean = false @bar) { field }')
+
     def does_not_accept_fragments_named_on():
         assert_syntax_error(
             'fragment on on on { on }', "Unexpected Name 'on'", (1, 10))

tests/language/test_printer.py

@@ -48,6 +48,16 @@ def correctly_prints_query_operation_with_artifacts():
             }
             """)
 
+    def correcty_prints_query_operation_with_variable_directive():
+        query_ast_with_variable_directive = parse(
+            'query ($foo: TestType = {a: 123}'
+            ' @testDirective(if: true) @test) { id }')
+        assert print_ast(query_ast_with_variable_directive) == dedent("""
+            query ($foo: TestType = {a: 123} @testDirective(if: true) @test) {
+              id
+            }
+            """)
+
     def correctly_prints_mutation_operation_with_artifacts():
         mutation_ast_with_artifacts = parse(
             'mutation ($foo: TestType) @testDirective { id, name }')