Internal Vue crash: v-if on component

[jods4]

Version

3.0.0-alpha.10

Reproduction link

https://jsfiddle.net/3d2twLq9/1/

Steps to reproduce

Open the console, click on the button. Vue does some bad stuff.

What is expected?

v-if is replaced by v-else, no error

What is actually happening?

Stuff crashes, apparently because slot content is evaluated before v-if, which results in null dereferences and then bad stuff.

---

This minimal repro stays usable after the crash (you could set a new some value and recover).
My own app is more complex and is unusable after this bug.

[jods4]

Using a component here is the key difference. If you do <div v-if='some'> instead then everything works fine.

[jods4]

@yyx990803 The simple repro is fixed but I'm still having issues in my project.
Not sure what I can do because it's a lot more complex than a simple repro.

That said, this fragment:

<ui-form
      v-if="selected != null"
      @save="updateGroup(selected)"
    >
<!-- ... more stuff inside -->
         <input
            type="checkbox"
            :value="right.name"
            v-model="selected.roles"
            style="margin-right: 12px;"
          />

Still executes code with selected equals to null.

Exception is caught and if I let it run it then fails with a stack overflow:

Any idea?

[yyx990803]

Well... can't really tell anything without a repro. If you can maybe extract part of your project into something runnable, I can take a look.

[jods4]

I'll try to see if I can come up with another repro... really not sure which bits are responsible for the problem after alpha.11

[jods4]

@yyx990803 I was working on other stuff and the bug went away with an unrelated change.
I have even less idea now what happened. It seems wrong that a null selected was accessed inside a slot that was under a v-if=selected but I can't reproduce it anymore.

Also can't exclude I was doing something stupid.

Should it pop up again I'll try to find a repro but I'm giving up for now.

[jods4]

@yyx990803 Got it.
It was hard but I managed to nail down a small repro.
https://jsfiddle.net/e635agws/15/
Click on the button with the dev tools open, you'll see that some.name is evaluated with some being null, even though that binding is inside a v-if="some".

[yyx990803]

78977c3