Internal error: illegal access (debugging ES6 proxy)

[iliakan]

I'm using node-inspector for node 0.11.13

I start node --debug-brk ..., open node-inspector and enter the code in Chrome. Everything's fine.

Then I press 'Continue' in Chrome and, after some time, in console:

Internal error: illegal access

There is no stack at all.

Is there a way to trace communication with v8 to see at which stage it happened? It looks like a node-inspector bug.

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[3y3]

What is your node-inspector version?

[iliakan]

node-inspector -v
v0.7.4

[3y3]

Is "pause on uncaught errors" enabled?

[iliakan]

Not enabled.

[3y3]

Ok, how I explain current situation:
Application was loaded and paused on first line. After that you start execution and application terminates with error Internal error: illegal access.
Are you think that reason for this error is attached inspector?
Or problem is in not displayed error stack?
You can't see stack trace bacause this is Uncaught error.
You can try to enable "pause on uncaught errors" - is this helpful?

---

А вообще я бы предпочел разобраться с этим на русском языке через почту 3y3@bk.ru

[iliakan]

The application does not terminate.
Web interface of Node Inspector terminates.

And yes, there is no stack.

P.S. Right now the code has changed quite a bit, when I see the problem the next time, I can try pause on uncaught errors or do something else if you recommend.

[iliakan]

@3y3 I made the commit for you: https://github.com/iliakan/javascript-nodejs/commit/d539f298644bfd0eaaa75e9cb8cd1d86843110c3

Probably, the project can be cleared off most stuff to demonstrate the error, but I believe you can easily run it as it is.

To see the error:

1. Install and run the project, see https://github.com/iliakan/javascript-nodejs/blob/master/Install.md (in Russian).
2. Run node-inspector, open node-inspector browser window.
3. Go http://127.0.0.1:3000/

You should see the error like this: http://ilyakantor.ru/screen/2014-08-05_2155.png

[unbornchikken]

I having the same issue. I already figured out that there is related to harmony proxies. If I place a breakpoint to a position where the current scope is behind a proxy call, in the call stack I can see many "Illegal access" lines. I think this issue is not related to node-inscpector, because I cannot debug my harmony Proxy based code in JetBrains Web Storm also, the above error happens,

[iliakan]

The Illegal access is indeed coming from proxies. On my codepath though, there seem to be no proxies.

[3y3]

@unbornchikken , can you post example of code?

[3y3]

@iliakan , I forked you commit and try to find the problem.

[unbornchikken]

Hello,

Of course, here it goes: http://1drv.ms/XSR4Qc

I've created a simple mocha unit test to reproduce this issue.

steps to reproduce:

npm install -g mocha
unarchive my repro project to a folder
npm install
launch node-inspector
mocha --debug-brk --harmony index
switch to node-inspector, refresh page, put a breakpoint to index.js line 11
launch debugging
nothing happens, debugging hangs up (except there should be an error message in the node.js console that says: illegal access buff)
pause debugging
red Internal error: Illegal access will appear in the node-inspector console

Cheers,
chikk

[unbornchikken]

Almost forgot: node version is 0.11.13

[unbornchikken]

It seems it's a v8 issue. I've opened it there:

https://code.google.com/p/v8/issues/detail?id=3510

[iliakan]

The V8 team is not going to fix that any time soon (https://code.google.com/p/v8/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Type%20Status%20Priority%20Owner%20Summary%20HW%20OS%20Area%20Stars&groupby=&sort=&id=3510)

Proxy breaks node-inspector, making things non-debuggable, so I'd suggest to evade Proxy in code now. That's mostly possible. And there's something node-inspector could do here, better than just diy with a strange error.

I'd suggest that node-inspector should catch this kind of error (is it possible)? And console.log a descriptive message, something like 'ES6 Proxy are not debuggable in V8 yet', and, if possible saying where the offending Proxy is (to get rid of it).

Doable?

[3y3]

@iliakan , can you confirm, that your project also has problems by reason of Proxy? (I forked your commit, but I can't start it - npm install fails on javascript-parser, but I see what you use --harmony flag)

About fixing: I have in plans switch to Blink object serialization algorithm, in other words - rewrite current place that emit this error. But it's not a small fix - is's a big job.
Also Node Inspector current target is "work same as Blink Dev Tools", but not "work better than Blink Dev Tools", therefore this fix has low priority for me.

[iliakan]

I would guess so. The error message looks like Proxy error.
I've reported an issue to koa-passport, that's the only place in the project which uses Proxy, hopefully @rkusa will fix it.

[MeanwhileMedia]

Thanks, this issue shed some light on my mystery problem. Have subscribed. Fingers crossed for some future compatibility fixes.

[bajtos]

FWIW, the upcoming io.js 1.0.0 release should ship a much more recent version of V8, you should give it a try and see if the issue has been fixed. https://iojs.org/

[metamatt]

This is a V8 problem (in its runtime debugger/reflection APIs), not a node-inspector problem per se.

For a project I work on, we patched the following functions in V8: Runtime_GetLocalPropertyNames, Runtime_GetLocalElementNames, Runtime_DebugGetProperty, Runtime_DebugConstructedBy to deal better with JSProxy, then rebuilt node from the patched source.

Those are the V8 3.14 (node 0.10.x) functions and they don't exist under those names in V8 3.28 (node 0.12.0), but I don't think the issue has actually been fixed as of V8 3.28. I haven't tried io.js. I did just try a quick test of node 0.12.0 with Proxy and node-inspector and still see Illegal access exceptions.

[MeanwhileMedia]

Thanks for that info @metamatt
I guess our only hope is to wait for a V8 fix. However, even when that happens, we will need node-inspector to support io.js so we can get at the newest v8. Looks like that may come just in time (#523)!

[benmarten]

I just ran into this problem... Is there any fix yet?

[egalpin]

Was also seeing this error, but based on this node-inspector issue thread, I upgraded to node 6.2.1 and the issue was resolved.

If you have the ability to upgrade to 6.2.1, it might be worth a try. Not sure how related the 2 issues are.

[huanghaiyang]

same problem.
node version v6.2.0

[mhcho-dev]

This happens on Chrome browser's debugger! with Proxy Object.

[iyobo]

Just verified that this is be resolved in node 7.7+