Method console.warn invoked with wrong context

[vla74]

Hi,

We're running Autobahn JS on various terminal types, including Samsung and LG Smart TVs (Chromium-based browsers).
With these Smart TVs, when the established connection is closed (for example after stopping the Crossbar server), we get JS errors like:

Uncaught TypeError: Illegal invocation

TypeError: Type error

In this case the AB connection's onclose handler is not called, and thereby our code is not aware that reconnection must be attempted.

This issue appeared from ABJS v19.10.1.
Connection handler self._transport.onclose calls:

log.warn("connection closed", reason, details);

https://github.com/crossbario/autobahn-js/blob/v19.10.1/packages/autobahn/lib/connection.js#L343

The log module defines its warn method as a direct reference to DOM console.warn:

var warn = console.warn;
exports.warn = warn;

https://github.com/crossbario/autobahn-js/blob/master/packages/autobahn/lib/log.js#L23

Execution of AB's log.warn does not cause issue on desktop browsers (Chrome, Firefox, Edge, IE11). However it fails on the affected Smart TVs because the warn Function is executed with a this context which is not the console object.
The Smart TV browsers may have a specific behaviour requiring this context (like redirecting the browser logs to an internal debugging system...).

To work on such platforms, Autobahn log module code should be something like:

var warn = console.warn.bind(console);

Note: AB's log.debug method should not be affected by this issue, as its code uses the console context.

Beyond the specific case of these Smart TV platforms, from a more general OOP point of view, the method of an object's instance should not be called outside of the context of this instance.

Thanks

[oberstet]

ok, thanks for reporting! so just to be sure:

1. while autobahn.log.debug works in your environment (samsung smart tvs), autobahn.log.warn does not work.
2. the fix is a one liner (as linked above): var warn = console.warn; => var warn = console.warn.bind(console);

?

[vla74]

You're welcome.

1. After enabling the AB debug mode, I confirm that log.debug does not cause any exception on the affected Smart TVs, while log.warn does.
2. Yes. In more details, I tested the 2 following fixes with the affected terminals, and both work:

• Compact version with bind:

var warn = console.warn.bind(console);

• Closure similar to the declaration of the debug function:

var warn = function () {
    console.warn.apply(console, arguments);
};

Function.prototype.bind normally requires an ECMAScript 5 compatible browser (http://kangax.github.io/compat-table/es5/#test-Function.prototype.bind), however I think that there's a polyfill embedded in ABJS (https://github.com/crossbario/autobahn-js/blob/master/packages/autobahn/lib/polyfill/function.js).

BTW, for the sake of consistency, let me suggest that debug and warn functions are declared the same way (so, probably using the bind method for both).

[hmistry-lz]

This is causing issue in IE 11. It breaks the add in that we are working on. It breaks on the same line as mentioned by @vla74
I am seeing below error on IE11

SCRIPT5022: InvalidAccessError
0.chunk.js (57211,9)
[bugsnag] Report not sent due to releaseStage/notifyReleaseStages configuration
{"code":1005,"wasClean":true}
SCRIPT65535: Invalid calling object
0.chunk.js (53095,7)

I have also enable debug mode in AB

[hmistry-lz]

@oberstet @om26er
If possible, Please share the timeline for this fix.

@vla74 have you done anything special to get around the issue you are facing while this bug gets fixed in AB?

[vla74]

@om26er @oberstet Thank you for the fix.

@hmistry-lz As we're also facing issue #485, we decided to stick to AB version <19.10.1, waiting for the availability of fixes. Otherwise a workaround might consist in redefining console.warn before import of AB asset (console.warn = console.warn.bind(console);), but this is not really something we wanted to operate in production.

[om26er]

@vla74 @hmistry-lz I have released autobahn-js 20.4.1, with contains the fix for this bug as well. Kindly try that.

[vla74]

@om26er We're not integrating Autobahn-js project directly but rather
autobahn-js-browser, and this one is not available in v20.4.1 yet. I can try as soon as you release an update.

[om26er]

I can try as soon as you release an update.

That is done now https://github.com/crossbario/autobahn-js-browser

[vla74]

Many thanks for this new release. I confirm that it solves the issue for our Smart TVs.

Note: It seems that this 20.4 branch introduced the use of async / await syntax. I've had to polyfill this.