Node: Print better error messages on RequireObjectCoercible error

[binarykitchen]

not sure how to explain this. my videomail.io app threw an uncaught error and had to debug deep to find out what this error message means:

Can't call method on [object Object]

really want to know what method is tried to be invocated here on what object? but seeing just [object Object] isn't very helpful. the responsible code line is this one:

// 7.2.1 RequireObjectCoercible(argument)
module.exports = function(it){
  if(it == undefined)throw TypeError("Can't call method on  " + it);
  return it;
};

as you can see, using nodejs 7.2.1 here and Ubuntu 16.10 on the server. but the server isn't relevant since this part of code has been browserified.

[addaleax]

What core are you running/reproduces the problem? Where is the snippet you posted from?

[binarykitchen]

i am afraid, this is hard to reproduce. this is just an Uncaught TypeError error i have caught with the window.onerror event handler by random within the www.videomail.io app

the snippet itself is part of the stack trace this error was thrown with. here a gist of that error but not sure if it is helpful: https://gist.github.com/binarykitchen/30ece5f6a7adc02d482e3c4120fa0df7

[addaleax]

with the window.onerror event handler

This sounds like it’s a frontend bug, not a Node bug, to me? This bug tracker is for problems with Node itself, so it might be a better idea to move this to https://github.com/nodejs/help or a Q&A site like StackOverflow unless you are sure that this is a problem with Node.

[binarykitchen]

@addaleax understand your comment. but then, this part of nodejs code has been browserified for the browser, hence still relevant i think.

for example "Can't call method on " + it could be "Can't call method on " + it.toString() instead so that there is more information than just [object Object]'

[evanlucas]

If this is browserified code, I think you may have better luck opening an issue on whatever the repo is for the module being browserified. As Anna suggested, feel free to move this to https://github.com/nodejs/help, but I'm going to go ahead and close as this doesn't appear to be an issue in core. Thanks!

[binarykitchen]

https://github.com/substack/node-browserify/issues/1724

[binarykitchen]

still no response from browserify

but still, i wonder why not to apply .toString() - this would help greatly and comes with no pitfalls. @addaleax

i could do a pr for that it this is ok?

[addaleax]

@binarykitchen I still don’t really know where the snippet you posted is from, how this bug relates to Node (it still reads like a frontend issue from everything you’ve said), or what your expected behaviour is.

i could do a pr for that it this is ok?

Sure – that might help clear a few things up anyway

[binarykitchen]

yeah, it's node, around these C++ lines (not sure which one of these)

https://github.com/nodejs/node/blob/98ddab411523f83eca9b5311529f8288379e550f/deps/v8/src/builtins/builtins-object.cc#L271
https://github.com/nodejs/node/blob/98ddab411523f83eca9b5311529f8288379e550f/deps/v8/src/builtins/builtins-string-gen.cc#L999

sorry, cannot do a pr since i am not skilled enough with C++ ... point is that the resulting JavaScript code should not be

throw TypeError("Can't call method on  " + it);

but something like

throw TypeError("Can't call method on  " + it.toString());

so that more information is printed and not [object Object]

[evanlucas]

Wouldn't the first implicitly call it.toString() though?

[binarykitchen]

right. then something else than toString(). maybe util.inspect() or something better which can deal with objects too.