[WIP] Support for __getattr__ and __setattr__

runtime/core.go

@@ -219,13 +219,23 @@ func GetItem(f *Frame, o, key *Object) (*Object, *BaseException) {
 // GetAttr returns the named attribute of o. Equivalent to the Python expression
 // getattr(o, name, def).
 func GetAttr(f *Frame, o *Object, name *Str, def *Object) (*Object, *BaseException) {
-	// TODO: Fall back to __getattr__.
 	getAttribute := o.typ.slots.GetAttribute
 	if getAttribute == nil {
 		msg := fmt.Sprintf("'%s' has no attribute '%s'", o.typ.Name(), name.Value())
 		return nil, f.RaiseType(AttributeErrorType, msg)
 	}
+
 	result, raised := getAttribute.Fn(f, o, name)
+	if raised != nil && raised.isInstance(AttributeErrorType) {
+		// Fall back to __getattr__ when __getattribute__ raised AttributeError
+		getAttr := o.typ.slots.GetAttr
+		if getAttr != nil {
+			f.RestoreExc(nil, nil)
+			result, raised = getAttr.Fn(f, o, name)
+		}
+	}
+
+	// Last resort: return the default
 	if raised != nil && raised.isInstance(AttributeErrorType) && def != nil {
 		f.RestoreExc(nil, nil)
 		result, raised = def, nil

runtime/slots.go

@@ -186,6 +186,26 @@ func (s *getAttributeSlot) wrapCallable(callable *Object) bool {
 	return true
 }
 
+type getAttrSlot struct {
+	Fn func(*Frame, *Object, *Str) (*Object, *BaseException)
+}
+
+func (s *getAttrSlot) makeCallable(t *Type, slotName string) *Object {
+	return newBuiltinFunction(slotName, func(f *Frame, args Args, kwargs KWArgs) (*Object, *BaseException) {
+		if raised := checkMethodArgs(f, slotName, args, t, StrType); raised != nil {
+			return nil, raised
+		}
+		return s.Fn(f, args[0], toStrUnsafe(args[1]))
+	}).ToObject()
+}
+
+func (s *getAttrSlot) wrapCallable(callable *Object) bool {
+	s.Fn = func(f *Frame, o *Object, name *Str) (*Object, *BaseException) {
+		return callable.Call(f, Args{o, name.ToObject()}, nil)
+	}
+	return true
+}
+
 type getSlot struct {
 	Fn func(*Frame, *Object, *Object, *Type) (*Object, *BaseException)
 }
@@ -388,6 +408,7 @@ type typeSlots struct {
 	GE           *binaryOpSlot
 	Get          *getSlot
 	GetAttribute *getAttributeSlot
+	GetAttr      *getAttrSlot
 	GetItem      *binaryOpSlot
 	GT           *binaryOpSlot
 	Hash         *unaryOpSlot

testing/class_test.py

@@ -40,6 +40,8 @@ def bar(self):
 assert foo.baz() == 'bar'
 
 foo.b = 10
+assert foo.b == 10
+
 del foo.b
 assert not hasattr(foo, 'b')
 try:
@@ -48,3 +50,19 @@ def bar(self):
   pass
 else:
   raise AssertionError
+
+
+spamdict = {}
+class Spam(object):
+  def __getattr__(self, key):
+    return spamdict[key]
+  def __setattr__(self, key, value):
+    spamdict[key] = value
+
+spam = Spam()
+spam.eggs = 'with eggs'
+assert spamdict == {'eggs': 'with eggs'}, "Change spam.eggs should update spamdict"
+assert spam.eggs == 'with eggs', "spam.eggs value should came from spamdict['eggs']"
+
+spamdict['eggs'] = 'with more spam'
+assert spam.eggs == 'with more spam', "Change spamdict['eggs'] should update spam.eggs"