this addresses bug - shouldnot #2067

[boazblake]

Description

shouldNotUpdate throws an uncaught exception: vnode._state is undefined (vnode.state in v2)

Motivation and Context

When shouldNotUpdate is true, we should also copy the rest of the state of the old vnode (children, instance, dom) on the new one. Otherwise on the next cycle, the old vnode is unbaked, and thus unfit for diff.(#2067 (comment))

#2067

How Has This Been Tested?

Not Yet

Types of changes

• [ x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation change

Checklist:

• [ x ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [ x ] I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• [ x ] All new and existing tests passed.
• I have updated docs/change-log.md

[boazblake]

@isiahmeadows let me know what tests to add - I saw @pygy had these

[dead-claudia]

Other than my nit, if you could find a way to test this, that'd be awesome. BTW, it may be challenging as I've struggled to reduce that repro personally. (You may have to start by explicitly rendering the large component trees and try to reduce it into a manageable test case from there by unnesting the recursion where possible.)