Reject back-to-back duplicate errors/messages

[benvinegar]

cc @getsentry/javascript

[benvinegar]

Refs #435

[LewisJEllis]

LGTM aside from one comment

[LewisJEllis]

I'd prefer this alternative function body:

return !!(!!a ^ !!b);

The xor operator makes it more obvious what's going on IMO, and this will always return a boolean; current version has some edge cases where it won't like isOnlyOneTruthy('', '') (returns empty string). Or if we're cool with always returning 0 or 1 instead of a boolean, we can further simplify to !!a ^ !!b.

[benvinegar]

Good suggestion, doing it.

[MaxBittker]

what about !!a != !!b?

[benvinegar]

what about !!a != !!b

Are they equivalent?

[MaxBittker]

i think green is the best color for bikesheds

[benvinegar]

Integration tests incoming.

[MaxBittker]

note to self/being paranoid - do we want to nullcheck values here first?

[benvinegar]

We assemble these objects ourselves, and other pieces of the code make the same assumption so I feel it's safe:

e.g. here's _trimPacket:

    _trimPacket: function(data) {
        // For now, we only want to truncate the two different messages
        // but this could/should be expanded to just trim everything
        var max = this._globalOptions.maxMessageLength;
        if (data.message) {
            data.message = truncate(data.message, max);
        }
        if (data.exception) {
            var exception = data.exception.values[0];
            exception.value = truncate(exception.value, max);
        }

        return data;
    },