Best way to log caught errors?

[OliverJAsh]

Goal: swimlane code by catching errors, and:

1. report error to Sentry with custom tags
2. log error in the best possible way

… whilst reporting uncaught exceptions to Sentry as well.

I want to swimlane my JS, so if one function fails, the next will run regardless. When there is an error, I want to capture it with Raven, and log it to the console.

var swimlane = function (options, fn) {
    try { fn(); } catch(e) {
        raven.captureException(e, options);
        // optionally console log the error
        // console.error(error);
    }
};

swimlane({ tags: { module: 'foo' } }, foo());
swimlane({ tags: { module: 'bar' } }, bar());

To do this, I have written a function similar to raven.wrap, exception it does not re-throw, thus allowing execution to continue.

However, I'm finding that logging the error the console is not easy. Each browser has its own way of logging the error to the console. For example, you might try:

console.error(error);

In Chrome, console.error creates a new error object and the argument is the message. So you end up with an error nested in an error:

http://jsbin.com/vimuxu/1/edit?js,output

In browsers that support the error.stack property (non-standard), I would like to log that. Otherwise, I would like to log the file name, line number, and column number. This logging is essentially what the browsers do automatically for uncaught exceptions.

Because of this, I would much rather let the browser automatically log my errors to the console as uncaught exceptions.

To do that, I could write a swimlane function that just catches the error and throws it in the next turn so it doesn't halt the current execution stack:

raven.install();

var swimlane = function (options, fn) {
    try { fn(); } catch(e) {
        setTimeout(function () { throw e; });
    }
};

swimlane({ tags: { module: 'foo' } }, foo());
swimlane({ tags: { module: 'bar' } }, bar());

The trouble then is I have no way of specifying my options (in this case, tags). I could use raven.setExtraContent/setTagsContext, but that just permanently updates the global options with the new tags.

The best of both worlds would be to capture the error and throw it in the next turn (for browser logging), but then it would be logged twice because raven is also listening for uncaught exceptions:

raven.install();

var swimlane = function (options, fn) {
    try { raven.context(options, fn); } catch(e) {
        setTimeout(function () { throw e; });
    }
};

swimlane({ tags: { module: 'foo' } }, foo());
swimlane({ tags: { module: 'bar' } }, bar());

Is there a happy medium? Perhaps you might be able to shed some light on where I'm going wrong. Or, perhaps you know of a good way to manually log errors across all browsers (stack in modern, file + line and col numbers in non-modern (i.e. IE 9)).

[dcramer]

You could call the context methods within setTimeout, but you're still going to likely see issues.

There's not really a solution here as JavaScript is a single interpreter and there's no way for us to understand your concept of a callstack (which is effectively what you're tweaking with the setTimeout).

The only real situation would be something like:

• Preserve the current context values
• Override with context in setTimeout
• throw error
• Restore context values'

We dont have an API for that, and tbh I'm not sure it's a good enough solution to warrant one upstream as re-throwing errors in such a fashion doesn't seem to be very standard.

[OliverJAsh]

Something like this, perhaps?

raven.install();

var swimlane = function (options, fn) {
    try { fn(); } catch(e) {
        setTimeout(function () {
            // 1. copy global options
            // 2. update global options with new options
            throw e;
            // 3. restore the copied global options from 1
        });
    }
};

swimlane({ tags: { module: 'foo' } }, foo());
swimlane({ tags: { module: 'bar' } }, bar());

Not sure how crazy this is.

[dcramer]

Yeah. Thats how you could solve it.