Handling recursive structures

[sarahzrf]

Certain kinds of recursive structures give me load errors. I did a little googling and found a solution in PyYAML (http://stackoverflow.com/a/29607120); does Camel support something like that? If not, would it be possible to patch support in?

[sarahzrf]

Actually, I'm working on trying to patch it in myself. It doesn't seem too hard so far...

[sarahzrf]

ok I figured out how to implement it, but... I've realized that, as I probably should've assumed that you already had, that PyYAML does not really mitigate the fact that loading circular structures is a hard problem... so never mind.

[sarahzrf]

For what it's worth, I still have my changes; if you think there'd be any worth in adding a finicky, confusingly-behaving cyclic-structure mode, I can reopen this.

[eevee]

I'm not sure offhand how I'd tackle this, but it is an interesting problem, and I didn't know about that feature. I'll leave this open and take a closer look whenever I mess with camel next.

[sarahzrf]

The patch I wrote does work, it's just that its behavior is potentially confusing and bug-producing (which is more or less inherited from PyYAML). In particular, it forces you to worry about whether child values have been loaded. For example, this code might well be incorrect:

def _load_weakset():
    w = WeakSet()
    vals, version = yield w
    w.update(vals)

Since vals might not be fully loaded at the time update is called, it might later get appended to, and the new value wouldn't make it it into w.