Handle races between user actions and transitions

[gaearon]

Router currently doesn't handle races between user actions and transitions well.

Say I'm on route /good, and /slow handler has this code (assuming abort() is fixed of course):

statics: {
  willTransitionTo(transition, params) {
    transition.wait(Promise.delay(3000).then(() => transition.abort()));

If I click a link to /slow, URL will change to /slow and will wait three seconds before going back to /good (because of aborted transition).

However if I click a link to /slow and then perform a Back myself (which will immediately change address to /good), the router will still invoke goBack, potentially throwing me out of the website.

Similarly, if I get tired of waiting and click a link to /another, when /slow is ready and its transition.abort() runs, it will force going back when I'm neither on /good nor on /slow anymore.

This is not just a problem with abortions: even if I just have a slow transition.wait() and click on a link while I'm waiting for transition to happen, router will happily take me there, but then all of a sudden will force the transition on me.

I propose the following rule of thumb for solving race problems in router: user intent must always override pending transitions. In other words, user clicking Back or clicking on a link should abort the pending transition. This behavior is most natural and matches what browser does.

I'm preparing a PR for that.

[ryanflorence]

I propose the following rule of thumb for solving race problems in router: user intent must always override pending transitions.

Agreed, can't wait for the PR :)

[gaearon]

It's actually there (#480) but not rebased yet. I think I can rebase tomorrow.