JS errors : calling native console.log() failed

[gmetais]

Hi,

Phantomas generates many errors when running on this page: http://www.lafermeduweb.net
The errors seems to be internal, but i've been struggling for 2 hours looking for the reason.

Here is a part of the log in verbose mode:

15:49:52.925 JS error: Error: phantomas: calling native console.log() failed ("TypeError: '["DOMqueriesByTagName","%s (in %s)","head","#document"]' is not a valid argument for 'Function.prototype.apply' (evaluating 'this.addOffender.apply')")!
15:49:52.925 Event jserror emitted
15:49:52.925 Error: phantomas: calling native console.log() failed ("TypeError: '["DOMqueriesByTagName","%s (in %s)","head","#document"]' is not a valid argument for 'Function.prototype.apply' (evaluating 'this.addOffender.apply')")!
15:49:52.926 Backtrace: sendMsg(): /Users/gaelmetais/Documents/GitHub/phantomas/core/scope.js @ 127 / addOffender(): /Users/gaelmetais/Documents/GitHub/phantomas/core/scope.js @ 157 / selectorTagNameSpy(): phantomjs://webpage.evaluate() @ 35 / unknown fn: /Users/gaelmetais/Documents/GitHub/phantomas/core/scope.js @ 210 / unknown fn: http://static.lafermeduweb.net/js/fdw-min.js @ 1 / unknown fn: http://static.lafermeduweb.net/js/fdw-min.js @ 1

Any idea why it is failing?

[gmetais]

I managed to understand the problem. It's when a website (or a JS library) overrides some JSON related functions.

• Mootools 1.2 overrides the window.JSON object, JSON.stringify and JSON.parse don't exist anymore. It's fine in scope.js because the stringify method is saved. But it's not in some other modules (example).
• Prototype 1.6 (and Mootools 1.2 too) creates an Array.prototype.toJSON function which get used by JSON.stringify (stackoverflow).

These problems got fixed in later releases.

Some example websites:
www.lafermeduweb.net uses Mootools 1.2.0
www.ratp.fr uses Prototype 1.6.1

Not an easy bug to fix. Maybe the cleanest way would be to add some Phantomas.JSONstringify and Phantomas.JSONparse functions which do not rely on Array/Object/Hash/String.prototype.toJSON.

[macbre]

@gmetais, thanks for investigating.

phantomas already copies the native console.log before site JS can modify it. The simple fix here is to do the same for JSON related functions.

[gmetais]

Be careful, there will still be a problem with:

Array.prototype.toJSON
Object.prototype.toJSON
Hash.prototype.toJSON
String.prototype.toJSON

By default, they don't exist in the browser. But the JSON.stringify function will look for them and use them if they get defined.

That's the touchy part of this fix.

[macbre]

Error: phantomas: calling native console.log() failed fixed in a9b5a9d.

However, there's still TypeError: 'undefined' is not a function (evaluating 'JSON.parse("{\"svgResources\":[]}")') caused by JSON.parse being removed - patched in 84e8af9

[gmetais]

Awesome, thank you!

[gmetais]

For your information, this bug is still occurring on https://www.washingtonpost.com

For the moment I can't find the reason :(