fix(runtime-core): should pause tracking deps when initializing legacy options

[HcySunYang]

close: #2521

[edison1105]

The second problem is not fixed.

[LinusBorg]

Yep. It seems we also need to pause Tracking in doWatch, not sure if we should just wrap the whole thing ...

[HcySunYang]

The second problem is not fixed.

I don't think the second problem is a bug or something that needs improvement. When the props change, the component does need to be updated, and I think the update is not equivalent to re-rendering, of course, it includes re-rendering.

Yep. It seems we also need to pause Tracking in doWatch, not sure if we should just wrap the whole thing ...

Not only the watch but also lifecycle hooks such as the created, I think it behaves similarly to setup: https://github.com/vuejs/vue-next/blob/master/packages/runtime-core/src/component.ts#L566-L573

[skirtles-code]

I'm unclear what people mean when they say 'the second problem'. In my original bug report I mentioned two problems, in bullet points 1 and 3. The contents of bullet point 2 were a necessary step in reproducing the problem in bullet point 3.

While it could be argued that the behaviour in bullet point 2 is also a bug (in my opinion it is) it is something that has been reported and discussed previously (see #1790 and #1181) and it wasn't what I was reporting in #2521.

[edison1105]

I'm unclear what people mean when they say 'the second problem'. In my original bug report I mentioned two problems, in bullet points 1 and 3. The contents of bullet point 2 were a necessary step in reproducing the problem in bullet point 3.

While it could be argued that the behaviour in bullet point 2 is also a bug (in my opinion it is) it is something that has been reported and discussed previously (see #1790 and #1181) and it wasn't what I was reporting in #2521.

[skirtles-code]

OK.

@HcySunYang The 'second problem' is not directly about re-rendering when the props change. That's just a necessary step along the way. The problem is what happens the next time the data changes after that.