component.loading never returns true if component fetches object returned nested on another object

pending_fetches isn't updated properly when you fetch an object with nested keyed objects.

Problems this causes

my reactive functions with @loading guards never complete
pending_fetches becomes a big memory hog when I have thousands of nested fetched objects

What is happening

Start at line 69 @ https://github.com/invisible-college/statebus/blob/master/statebus.js. There is a comment about counting keys that arrived on a nested object, with a subsequent call to bus.route.

Now imagine that we fetch an object that was nested when it arrived. Here's what happens:

!fetches_out[key] returns true, so route is called with fetch and the key
route calls run_handler
run_handler adds the key to pending_fetches in the case of a fetch (line 487).

That key will never be removed from pending_fetches. The only time that keys are removed from pending_fetches is on pub, but pub won't be called for objects that arrived nested on another object.

What it looks like in my application

First, I modified statebus.js's loading_keys function to show which keys a function is waiting on, and whether that key is actually already in cache:

function loading_keys (keys) {
    // Do any of these keys have outstanding gets?
    // console.log('Loading: pending_keys is', pending_fetches)
    for (var i=0; i<keys.length; i++){
        if (pending_fetches[keys[i]]) {
            console.log("loading_keys: still loading", keys[i], fetch(keys[i]))
            return true
        }
    }
    return false
}

Second, I have a reactive function that fetches /strategies. By the time this reactive function is called, /strategies is already in cache because it was nested in a previously fetched object. This reactive function has an @loading guard.

Here's the console output:

Is that enough info, or do you need a minimal test case?

invisible-college / statebus

component.loading never returns true if component fetches object returned nested on another object #16