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// Copyright 2016 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package grumpy
import (
"fmt"
"reflect"
)
type typeFlag int
const (
// Set when instances can be created via __new__. This is the default.
// We need to be able to prohibit instantiation of certain internal
// types like NoneType. CPython accomplishes this via tp_new == NULL but
// we don't have a tp_new.
typeFlagInstantiable typeFlag = 1 << iota
// Set when the type can be used as a base class. This is the default.
// Corresponds to the Py_TPFLAGS_BASETYPE flag in CPython.
typeFlagBasetype typeFlag = 1 << iota
typeFlagDefault = typeFlagInstantiable | typeFlagBasetype
)
// Type represents Python 'type' objects.
type Type struct {
Object
name string `attr:"__name__"`
basis reflect.Type
bases []*Type
mro []*Type
flags typeFlag
slots typeSlots
}
var basisTypes = map[reflect.Type]*Type{
objectBasis: ObjectType,
typeBasis: TypeType,
}
// newClass creates a Python type with the given name, base classes and type
// dict. It is similar to the Python expression 'type(name, bases, dict)'.
func newClass(f *Frame, meta *Type, name string, bases []*Type, dict *Dict) (*Type, *BaseException) {
numBases := len(bases)
if numBases == 0 {
return nil, f.RaiseType(TypeErrorType, "class must have base classes")
}
var basis reflect.Type
for _, base := range bases {
if base.flags&typeFlagBasetype == 0 {
format := "type '%s' is not an acceptable base type"
return nil, f.RaiseType(TypeErrorType, fmt.Sprintf(format, base.Name()))
}
basis = basisSelect(basis, base.basis)
}
if basis == nil {
return nil, f.RaiseType(TypeErrorType, "class layout error")
}
t := newType(meta, name, basis, bases, dict)
// Populate slots for any special methods overridden in dict.
slotsValue := reflect.ValueOf(&t.slots).Elem()
for i := 0; i < numSlots; i++ {
dictFunc, raised := dict.GetItemString(f, slotNames[i])
if raised != nil {
return nil, raised
}
if dictFunc != nil {
slotField := slotsValue.Field(i)
slotValue := reflect.New(slotField.Type().Elem())
if slotValue.Interface().(slot).wrapCallable(dictFunc) {
slotField.Set(slotValue)
}
}
}
if err := prepareType(t); err != "" {
return nil, f.RaiseType(TypeErrorType, err)
}
// Set the __module__ attr if it's not already specified.
mod, raised := dict.GetItemString(f, "__module__")
if raised != nil {
return nil, raised
}
if mod == nil {
if raised := dict.SetItemString(f, "__module__", builtinStr.ToObject()); raised != nil {
return nil, raised
}
}
return t, nil
}
func newType(meta *Type, name string, basis reflect.Type, bases []*Type, dict *Dict) *Type {
return &Type{
Object: Object{typ: meta, dict: dict},
name: name,
basis: basis,
bases: bases,
flags: typeFlagDefault,
}
}
func newBasisType(name string, basis reflect.Type, basisFunc interface{}, base *Type) *Type {
if _, ok := basisTypes[basis]; ok {
logFatal(fmt.Sprintf("type for basis already exists: %s", basis))
}
if basis.Kind() != reflect.Struct {
logFatal(fmt.Sprintf("basis must be a struct not: %s", basis.Kind()))
}
if basis.NumField() == 0 {
logFatal(fmt.Sprintf("1st field of basis must be base type's basis"))
}
if basis.Field(0).Type != base.basis {
logFatal(fmt.Sprintf("1st field of basis must be base type's basis not: %s", basis.Field(0).Type))
}
basisFuncValue := reflect.ValueOf(basisFunc)
basisFuncType := basisFuncValue.Type()
if basisFuncValue.Kind() != reflect.Func || basisFuncType.NumIn() != 1 || basisFuncType.NumOut() != 1 ||
basisFuncType.In(0) != reflect.PtrTo(objectBasis) || basisFuncType.Out(0) != reflect.PtrTo(basis) {
logFatal(fmt.Sprintf("expected basis func of type func(*Object) *%s", nativeTypeName(basis)))
}
t := newType(TypeType, name, basis, []*Type{base}, nil)
t.slots.Basis = &basisSlot{func(o *Object) reflect.Value {
return basisFuncValue.Call([]reflect.Value{reflect.ValueOf(o)})[0].Elem()
}}
basisTypes[basis] = t
return t
}
func newSimpleType(name string, base *Type) *Type {
return newType(TypeType, name, base.basis, []*Type{base}, nil)
}
// prepareBuiltinType initializes the builtin typ by populating dict with
// struct field descriptors and slot wrappers, and then calling prepareType.
func prepareBuiltinType(typ *Type, init builtinTypeInit) {
dict := map[string]*Object{"__module__": builtinStr.ToObject()}
if init != nil {
init(dict)
}
// For basis types, export field descriptors.
if basis := typ.basis; basisTypes[basis] == typ {
numFields := basis.NumField()
for i := 0; i < numFields; i++ {
field := basis.Field(i)
if attr := field.Tag.Get("attr"); attr != "" {
fieldMode := fieldDescriptorRO
if mode := field.Tag.Get("attr_mode"); mode == "rw" {
fieldMode = fieldDescriptorRW
}
dict[attr] = makeStructFieldDescriptor(typ, field.Name, attr, fieldMode)
}
}
}
// Create dict entries for slot methods.
slotsValue := reflect.ValueOf(&typ.slots).Elem()
for i := 0; i < numSlots; i++ {
slotField := slotsValue.Field(i)
if !slotField.IsNil() {
slot := slotField.Interface().(slot)
if fun := slot.makeCallable(typ, slotNames[i]); fun != nil {
dict[slotNames[i]] = fun
}
}
}
typ.setDict(newStringDict(dict))
if err := prepareType(typ); err != "" {
logFatal(err)
}
}
// prepareType calculates typ's mro and inherits its flags and slots from its
// base classes.
func prepareType(typ *Type) string {
typ.mro = mroCalc(typ)
if typ.mro == nil {
return fmt.Sprintf("mro error for: %s", typ.name)
}
for _, base := range typ.mro {
if base.flags&typeFlagInstantiable == 0 {
typ.flags &^= typeFlagInstantiable
}
if base.flags&typeFlagBasetype == 0 {
typ.flags &^= typeFlagBasetype
}
}
// Inherit slots from typ's mro.
slotsValue := reflect.ValueOf(&typ.slots).Elem()
for i := 0; i < numSlots; i++ {
slotField := slotsValue.Field(i)
if slotField.IsNil() {
for _, base := range typ.mro {
baseSlotFunc := reflect.ValueOf(base.slots).Field(i)
if !baseSlotFunc.IsNil() {
slotField.Set(baseSlotFunc)
break
}
}
}
}
return ""
}
// Precondition: At least one of seqs is non-empty.
func mroMerge(seqs [][]*Type) []*Type {
var res []*Type
numSeqs := len(seqs)
hasNonEmptySeqs := true
for hasNonEmptySeqs {
var cand *Type
for i := 0; i < numSeqs && cand == nil; i++ {
// The next candidate will be absent from or at the head
// of all lists. If we try a candidate and we find it's
// somewhere past the head of one of the lists, reject.
seq := seqs[i]
if len(seq) == 0 {
continue
}
cand = seq[0]
RejectCandidate:
for _, seq := range seqs {
numElems := len(seq)
for j := 1; j < numElems; j++ {
if seq[j] == cand {
cand = nil
break RejectCandidate
}
}
}
}
if cand == nil {
// We could not find a candidate meaning that the
// hierarchy is inconsistent.
return nil
}
res = append(res, cand)
hasNonEmptySeqs = false
for i, seq := range seqs {
if len(seq) > 0 {
if seq[0] == cand {
// Remove the candidate from all lists
// (it will only be found at the head of
// any list because otherwise it would
// have been rejected above.)
seqs[i] = seq[1:]
}
if len(seqs[i]) > 0 {
hasNonEmptySeqs = true
}
}
}
}
return res
}
func mroCalc(t *Type) []*Type {
seqs := [][]*Type{{t}}
for _, b := range t.bases {
seqs = append(seqs, b.mro)
}
seqs = append(seqs, t.bases)
return mroMerge(seqs)
}
func toTypeUnsafe(o *Object) *Type {
return (*Type)(o.toPointer())
}
// ToObject upcasts t to an Object.
func (t *Type) ToObject() *Object {
return &t.Object
}
// Name returns t's name field.
func (t *Type) Name() string {
return t.name
}
// FullName returns t's fully qualified name including the module.
func (t *Type) FullName(f *Frame) (string, *BaseException) {
moduleAttr, raised := t.Dict().GetItemString(f, "__module__")
if raised != nil {
return "", raised
}
if moduleAttr == nil {
return t.Name(), nil
}
if moduleAttr.isInstance(StrType) {
if s := toStrUnsafe(moduleAttr).Value(); s != "__builtin__" {
return fmt.Sprintf("%s.%s", s, t.Name()), nil
}
}
return t.Name(), nil
}
func (t *Type) isSubclass(super *Type) bool {
for _, b := range t.mro {
if b == super {
return true
}
}
return false
}
func (t *Type) mroLookup(f *Frame, name *Str) (*Object, *BaseException) {
for _, t := range t.mro {
v, raised := t.Dict().GetItem(f, name.ToObject())
if v != nil || raised != nil {
return v, raised
}
}
return nil, nil
}
var typeBasis = reflect.TypeOf(Type{})
func typeBasisFunc(o *Object) reflect.Value {
return reflect.ValueOf(toTypeUnsafe(o)).Elem()
}
// TypeType is the object representing the Python 'type' type.
//
// Don't use newType() since that depends on the initialization of
// TypeType.
var TypeType = &Type{
name: "type",
basis: typeBasis,
bases: []*Type{ObjectType},
flags: typeFlagDefault,
slots: typeSlots{Basis: &basisSlot{typeBasisFunc}},
}
func typeCall(f *Frame, callable *Object, args Args, kwargs KWArgs) (*Object, *BaseException) {
t := toTypeUnsafe(callable)
newFunc := t.slots.New
if newFunc == nil {
return nil, f.RaiseType(TypeErrorType, fmt.Sprintf("type %s has no __new__", t.Name()))
}
o, raised := newFunc.Fn(f, t, args, kwargs)
if raised != nil {
return nil, raised
}
if init := o.Type().slots.Init; init != nil {
if _, raised := init.Fn(f, o, args, kwargs); raised != nil {
return nil, raised
}
}
return o, nil
}
// typeGetAttribute is very similar to objectGetAttribute except that it uses
// MRO to resolve dict attributes rather than just the type's own dict and the
// exception message is slightly different.
func typeGetAttribute(f *Frame, o *Object, name *Str) (*Object, *BaseException) {
t := toTypeUnsafe(o)
// Look for a data descriptor in the metaclass.
var metaGet *getSlot
metaType := t.typ
metaAttr, raised := metaType.mroLookup(f, name)
if raised != nil {
return nil, raised
}
if metaAttr != nil {
metaGet = metaAttr.typ.slots.Get
if metaGet != nil && (metaAttr.typ.slots.Set != nil || metaAttr.typ.slots.Delete != nil) {
return metaGet.Fn(f, metaAttr, t.ToObject(), metaType)
}
}
// Look in dict of this type and its bases.
attr, raised := t.mroLookup(f, name)
if raised != nil {
return nil, raised
}
if attr != nil {
if get := attr.typ.slots.Get; get != nil {
return get.Fn(f, attr, None, t)
}
return attr, nil
}
// Use the (non-data) descriptor from the metaclass.
if metaGet != nil {
return metaGet.Fn(f, metaAttr, t.ToObject(), metaType)
}
// Return the ordinary attr from metaclass.
if metaAttr != nil {
return metaAttr, nil
}
msg := fmt.Sprintf("type object '%s' has no attribute '%s'", t.Name(), name.Value())
return nil, f.RaiseType(AttributeErrorType, msg)
}
func typeNew(f *Frame, t *Type, args Args, kwargs KWArgs) (*Object, *BaseException) {
switch len(args) {
case 0:
return nil, f.RaiseType(TypeErrorType, "type() takes 1 or 3 arguments")
case 1:
return args[0].typ.ToObject(), nil
}
// case 3+
if raised := checkMethodArgs(f, "__new__", args, StrType, TupleType, DictType); raised != nil {
return nil, raised
}
name := toStrUnsafe(args[0]).Value()
bases := toTupleUnsafe(args[1]).elems
dict := toDictUnsafe(args[2])
baseTypes := make([]*Type, len(bases))
meta := t
for i, o := range bases {
if !o.isInstance(TypeType) {
s, raised := Repr(f, o)
if raised != nil {
return nil, raised
}
return nil, f.RaiseType(TypeErrorType, fmt.Sprintf("not a valid base class: %s", s.Value()))
}
// Choose the most derived metaclass among all the bases to be
// the metaclass for the new type.
if o.typ.isSubclass(meta) {
meta = o.typ
} else if !meta.isSubclass(o.typ) {
msg := "metaclass conflict: the metaclass of a derived class must " +
"a be a (non-strict) subclass of the metaclasses of all its bases"
return nil, f.RaiseType(TypeErrorType, msg)
}
baseTypes[i] = toTypeUnsafe(o)
}
ret, raised := newClass(f, meta, name, baseTypes, dict)
if raised != nil {
return nil, raised
}
return ret.ToObject(), nil
}
func typeRepr(f *Frame, o *Object) (*Object, *BaseException) {
s, raised := toTypeUnsafe(o).FullName(f)
if raised != nil {
return nil, raised
}
return NewStr(fmt.Sprintf("<type '%s'>", s)).ToObject(), nil
}
func initTypeType(map[string]*Object) {
TypeType.typ = TypeType
TypeType.slots.Call = &callSlot{typeCall}
TypeType.slots.GetAttribute = &getAttributeSlot{typeGetAttribute}
TypeType.slots.New = &newSlot{typeNew}
TypeType.slots.Repr = &unaryOpSlot{typeRepr}
}
// basisParent returns the immediate ancestor of basis, which is its first
// field. Returns nil when basis is objectBasis (the root of basis hierarchy.)
func basisParent(basis reflect.Type) reflect.Type {
if basis == objectBasis {
return nil
}
return basis.Field(0).Type
}
// basisSelect returns b1 if b2 inherits from it, b2 if b1 inherits from b2,
// otherwise nil. b1 can be nil in which case b2 is always returned.
func basisSelect(b1, b2 reflect.Type) reflect.Type {
if b1 == nil {
return b2
}
// Search up b1's inheritance chain to see if b2 is present.
basis := b1
for basis != nil && basis != b2 {
basis = basisParent(basis)
}
if basis != nil {
return b1
}
// Search up b2's inheritance chain to see if b1 is present.
basis = b2
for basis != nil && basis != b1 {
basis = basisParent(basis)
}
if basis != nil {
return b2
}
return nil
}
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