V8 v8.7.220.25 bug

[Angelo Dell'Aera]

Hi all,

first post here. My name is Angelo and I am the maintainer of STPyV8, a 

Google V8 Python wrapper [1]. 

I already had a private a conversation with Camillo Bruni about this issue

and he suggested me to post details here as I reasonably spotted a bug 

in V8 branch 8.7.

While attempting to generate a STPyV8 release for the V8 branch 8.7 

(v8.7.220.25), 3 STPyV8 tests failed (see later for details).

While diving into details I noticed that the issue reasonably happens at

https://github.com/area1/stpyv8/blob/master/src/Wrapper.cpp#L715

In particular I noticed that if STPyV8 is compiled versus V8 <= 8.6 the else 

branch is executed. Using V8 8.7 the if branch is executed instead. Which 

seems to indicate some changes in IsExternal.

Tried taking a look at the git log and it seems like IsExternal went through 

some changes in the 8.7 branch. But, at the same time, it seems like this 

just happened for String objects and not for Object objects (double-checked 

that in all the three failing tests info.Data() is an object). Camillo confirmed

that changes affected String::IsExternal and not Value::IsExternal. 

Spent some time looking at the latest changes (the latest working release 

embeds V8 v8.6.395.25) but unfortunately I was not able to figure out which 

changes are potentially breaking my code. 

I performed another quick and dirty test and built STPyV8 using V8 v8.8.278.3. 

And the STPyV8 tests are working fine again. And again the correct if branch

is executed in STPyV8.

I have still not performed tests using a debug build to try to figure out some 

potentially additional details but the last test seems to confirm the presence 

of a bug in the branch 8.7.

Thanks and regards,

Angelo

[1] https://github.com/area1/stpyv8

---- STPyV8 tests logs ----

============================= test session starts ==============================

platform linux -- Python 3.7.9, pytest-6.0.1, py-1.9.0, pluggy-0.13.1

rootdir: /home/buffer/development/stpyv8

plugins: mock-3.1.1, cov-2.10.1

collected 52 items

tests/test_Context.py ....                                               [  7%]

tests/test_Engine.py .........                                           [ 25%]

tests/test_Isolate.py ..                                                 [ 28%]

tests/test_Multithread.py ..                                             [ 32%]

tests/test_Wrapper.py ...F.........F....................F                [100%]

=================================== FAILURES ===================================

_____________________________ TestWrapper.testCall _____________________________

self = <test_Wrapper.TestWrapper testMethod=testCall>

    def testCall(self):

        class Hello(object):

            def __call__(self, name):

                return "hello " + name

        class Global(STPyV8.JSClass):

            hello = Hello()

        with STPyV8.JSContext(Global()) as ctxt:

>           self.assertEqual("hello world", ctxt.eval("hello('world')"))

E           TypeError: TypeError: 'JSObject' object is not callable (  @ 1 : 0 )  -> hello('world')

tests/test_Wrapper.py:210: TypeError

_______________________ TestWrapper.testGetterAndSetter ________________________

self = <test_Wrapper.TestWrapper testMethod=testGetterAndSetter>

    def testGetterAndSetter(self):

        class Global(STPyV8.JSClass):

           def __init__(self, testval):

               self.testval = testval

        with STPyV8.JSContext(Global("Test Value A")) as ctxt:

           self.assertEqual("Test Value A", ctxt.locals.testval)

           ctxt.eval("""

               this.__defineGetter__("test", function() {

                   return this.testval;

               });

               this.__defineSetter__("test", function(val) {

                   this.testval = val;

               });

           """)

>          self.assertEqual("Test Value A",  ctxt.locals.test)

E          AttributeError: '[object Object]' object has no attribute 'test'

tests/test_Wrapper.py:784: AttributeError

____________________________ TestWrapper.testWatch _____________________________

self = <test_Wrapper.TestWrapper testMethod=testWatch>

    def testWatch(self):

        class Obj(STPyV8.JSClass):

            def __init__(self):

                self.p = 1

        class Global(STPyV8.JSClass):

            def __init__(self):

                self.o = Obj()

        with STPyV8.JSContext(Global()) as ctxt:

            ctxt.eval("""

            o.watch("p", function (id, oldval, newval) {

                return oldval + newval;

            });

            """)

            self.assertEqual(1, ctxt.eval("o.p"))

>           ctxt.eval("o.p = 2;")

E           TypeError: TypeError: 'Obj' object is not callable (  @ 1 : 4 )  -> o.p = 2;

tests/test_Wrapper.py:876: TypeError

=========================== short test summary info ============================

FAILED tests/test_Wrapper.py::TestWrapper::testCall - TypeError: TypeError: '...

FAILED tests/test_Wrapper.py::TestWrapper::testGetterAndSetter - AttributeErr...

FAILED tests/test_Wrapper.py::TestWrapper::testWatch - TypeError: TypeError: ...

========================= 3 failed, 49 passed in 3.25s =========================