Bug with old element recycling (V1)

I found this problem with V1, and I’m reporting it in case it remains relevant for V2.

The problem is that the old-body recycling seems to presume the body is not null, when it sometimes is. The fault is in this code:

function findDonor(node, newParent, oldParent, fromIdx, toIdx) {
    var newIsView = u.isArr(node);
    var newKey = newIsView ? getViewKey(node[1], node[2]) : node.key;
    var oldKeys = oldParent.hasKeys;
    var newKeys = newParent.hasKeys;
    var oldBody = oldParent.body;
    var newBody = newParent.body;

    // fast exact match by key
    if (newKey !== null && oldKeys) {
        var idx = u.keyedIdx(newKey, oldBody, newIsView ? node[0] : null, fromIdx, toIdx);
        if (idx > -1)
            return [idx, DONOR_NODE];
        return null;
    }

    // if from or to > newbody length, return null
    // todo: from keys here
    fromIdx = fromIdx || 0;
    if (fromIdx > oldBody.length - 1) return null; 
    // ^^^ repeatedly and consistently get oldBody is null or oldBody.length is null here
    toIdx = toIdx === 0 ? 0 : toIdx || oldBody.length - 1;
...

To resolve it, I simply changed the marked line to:

    if (!oldBody || fromIdx > oldBody.length - 1) return null; 

Unexpected is that the error varies between oldBody and oldBody.length.

Note that to produce a replication would require considerable time and effort since the displays are complex and would need to be (tediously) whittled down to the simplest form that reproduces the error. I don’t know if it’s worth investing the effort to do that, yet.

[lawrence-dol]

@leeoniya

is any porting to v2 on your horizon?

Yes, very much so. But I have to deliver the initial release over for QA first. So far the only complication that may take a little time to work through is my post-generation augmentation of the primary view based on host data which incorporates addressing into and searching the display grid. The rest I expect to be basic grunt work.

I expect to get to V2 before the end of this month.

[leeoniya]

sure, go for it