Source code for py_gql.utilities.type_info

# -*- coding: utf-8 -*-

from typing import Callable, List, Optional, Sequence, TypeVar, Union

from .._utils import find_one
from ..exc import UnknownEnumValue, UnknownType
from ..lang.visitor import DispatchingVisitor
from ..schema import (
from ..schema.introspection import (

T = TypeVar("T")

OptList = List[Optional[T]]

def _peek(
    lst: Sequence[T], count: int = 1, default: Optional[T] = None
) -> Optional[T]:
    return lst[-1 * count] if len(lst) >= count else default

def _or_none(value: T, predicate: Callable[[T], bool] = bool) -> Optional[T]:
    return value if predicate(value) else None

def _get_field_def(schema, parent_type, field):
    name =
    if parent_type is schema.query_type:
        if name ==
        if name ==

    if (
        isinstance(parent_type, GraphQLCompositeType)
        and name ==

    if isinstance(parent_type, (ObjectType, InterfaceType)):
        return parent_type.field_map.get(name, None)

    return None

# This is a very basic re-implementation of the reference javascript
# implementation which is compatible with our version of AST visitors
# and it can most likley be improved.
[docs]class TypeInfoVisitor(DispatchingVisitor): """ Utility visitor that recurisvely track the current types and field definitions while traversing a Document. All tracked types are considered with regards to the provided schema, however unknown types and other unexpected errors will be downgraded to null values in order to not crash the traversal. This leaves the consumer responsible to handle such cases. Warning: When using this alongside other visitors (such as when using :class:`py_gql.lang.visitor.ParallelVisitor`), this visitor **must** to be the first one to visit the nodes in order for the information provided donwstream to be accurate. Args: schema (py_gql.schema.Schema): Reference schema to extract types from Attributes: type (Optional[py_gql.schema.ObjectType]): Current type if applicable parent_typ (Optional[py_gql.schema.ObjectType]): Current type if applicable_stack, 1) input_typ (Optional[py_gql.schema.InputObjectType]): Current input type if applicable (when visiting arguments) parent_input_typ (Optional[py_gql.schema.InputObjectType]): Current parent input type if applicable (when visiting input objects) fiel (Optional[py_gql.schema.Field]): Current field definition if applicable (when visiting object) input_value_def (Optional[Union[py_gql.schema.Argument, \ py_gql.schema.InputField]]): Current input value definition (e.g. arg def, input field) if applicable """ __slots__ = ( "_schema", "_type_stack", "_input_type_stack", "_parent_type_stack", "_field_stack", "_input_value_def_stack", "directive", "argument", "enum_value", ) def __init__(self, schema): self._schema = schema self._type_stack = [] # type: OptList[ObjectType] self._parent_type_stack = [] # type: OptList[ObjectType] self._input_type_stack = [] # type: OptList[InputObjectType] self._field_stack = [] # type: OptList[Field] self._input_value_def_stack = ( [] ) # type: OptList[Union[Argument, InputField]] self.directive = None # type: Optional[Directive] self.argument = None # type: Optional[Argument] self.enum_value = None # type: Optional[EnumValue] @property def type(self) -> Optional[ObjectType]: return _peek(self._type_stack) @property def parent_type(self) -> Optional[ObjectType]: return _peek(self._parent_type_stack, 1) @property def input_type(self) -> Optional[InputObjectType]: return _peek(self._input_type_stack, 1) @property def parent_input_type(self) -> Optional[InputObjectType]: return _peek(self._input_type_stack, 2) @property def field(self) -> Optional[Field]: return _peek(self._field_stack) @property def input_value_def(self) -> Optional[Union[Argument, InputField]]: return _peek(self._input_value_def_stack) def _get_field_def(self, node): parent_type = self.parent_type return ( _get_field_def(self._schema, parent_type, node) if parent_type else None ) def _type_from_ast(self, type_node): try: return self._schema.get_type_from_literal(type_node) except UnknownType: return None def _leave_input_value(self): self._input_type_stack.pop() self._input_value_def_stack.pop() def enter_selection_set(self, node): named_type = unwrap_type(self.type) self._parent_type_stack.append( _or_none(named_type, lambda x: isinstance(x, GraphQLCompositeType)) ) return node def leave_selection_set(self, _node): self._parent_type_stack.pop() def enter_field(self, node): field_def = self._get_field_def(node) self._field_stack.append(field_def) if field_def: self._type_stack.append(_or_none(field_def.type, is_output_type)) else: self._type_stack.append(None) return node def leave_field(self, _node): self._type_stack.pop() self._field_stack.pop() def enter_directive(self, node): self.directive = self._schema.directives.get( return node def leave_directive(self, _node): self.directive = None def enter_operation_definition(self, node): type_ = { "query": self._schema.query_type, "mutation": self._schema.mutation_type, "subscription": self._schema.subscription_type, }.get(node.operation, None) self._type_stack.append( type_ if isinstance(type_, ObjectType) else None ) return node def leave_operation_definition(self, _node): self._type_stack.pop() def enter_fragment_definition(self, node): self._type_stack.append( _or_none(self._type_from_ast(node.type_condition), is_output_type) ) return node def leave_fragment_definition(self, _node): self._type_stack.pop() def enter_inline_fragment(self, node): if node.type_condition: self._type_stack.append( _or_none( self._type_from_ast(node.type_condition), is_output_type ) ) else: self._type_stack.append(_or_none(self.type, is_output_type)) return node def leave_inline_fragment(self, _node): self._type_stack.pop() def enter_variable_definition(self, node): self._input_type_stack.append( _or_none(self._type_from_ast(node.type), is_input_type) ) return node def leave_variable_definition(self, _node): self._input_type_stack.pop() def enter_argument(self, node): ctx = self.directive or self.field if ctx: name = self.argument = find_one(ctx.arguments, lambda a: == name) self._input_value_def_stack.append(self.argument) self._input_type_stack.append( self.argument.type if self.argument and is_input_type(self.argument.type) else None ) else: self.argument = None self._input_type_stack.append(None) self._input_value_def_stack.append(None) return node def leave_argument(self, _node): self.argument = None self._leave_input_value() def enter_list_value(self, node): list_type = nullable_type(self.input_type) item_type = ( unwrap_type(list_type) if isinstance(list_type, ListType) else None ) self._input_type_stack.append( _or_none(item_type, is_input_type) if item_type is not None else None ) # List positions never have a default value. self._input_value_def_stack.append(None) return node def leave_list_value(self, _node): self._leave_input_value() def enter_object_field(self, node): object_type = unwrap_type(self.input_type) if isinstance(object_type, InputObjectType): name = field_def = find_one(object_type.fields, lambda f: == name) self._input_value_def_stack.append(field_def) self._input_type_stack.append( field_def.type if field_def and is_input_type(field_def.type) else None ) else: self._input_type_stack.append(None) self._input_value_def_stack.append(None) return node def leave_object_field(self, _node): self._leave_input_value() def enter_enum_value(self, node): enum = unwrap_type(self.input_type) if isinstance(enum, EnumType): try: self.enum_value = enum.get_value(node.value) except UnknownEnumValue: self.enum_value = None return node def leave_enum_value(self, _node): self.enum_value = None