fix(shared): normalize undefined styles to empty object

[nVitius]

Currently, setting v-bind:style to a value that can compute to undefined will remove any styles on the element when it does return undefined. I ran into this issue when using v-show along with an undefined style binding.

This patch makes it so that the normalizeStyle function will convert undefined/null bindings to an empty object instead. I feel like this is a good place to add the check, but it is my first patch on this repo. If anyone can think of a better place to do this, I will change it.

[nVitius]

@yyx990803 Thanks for the review. I made the requested changes.

[Justineo]

Thank you for the PR. Can you make a minimal reproduction for the issue you are trying to fix?

I tried to make a repro but it does work as expected (v-show + :style="undefined").

And according to the coercion behavior for Vue 3, undefined bindings should lead to the removal of the attribute. Always normalizing undefined to {} will change this behavior.

[nVitius]

@Justineo I spent some time in the SFC playground today, trying to get a reproduction working (not working?).
I could not replicate the issue on there. From what I could tell, the compiled JS I got in the playground was the same as the JS I saw in the library that had the issue. Not really sure what to make of this.

I don't really have any more time to spend on setting trying to reproduce the issue. We fixed it in the library by using an empty object instead of undefined. I'm okay with closing this issue. Thanks for your help.

And according to the coercion behavior for Vue 3, undefined bindings should lead to the removal of the attribute. Always normalizing undefined to {} will change this behavior.

This is really interesting to know, thanks. For what it's worth, I was getting an empty style, as opposed to the attribute being removed: <div style="">.

[yyx990803]

I was able to reproduce this: link

(Clicking "remove" should not cause the input to be shown)

[yyx990803]

After looking into it I believe the more proper fix is ensuring style patching always respect v-show's inline display value (there was already logic in there but not covering the removal case)

[nVitius]

@yyx990803 Thanks for the help with diagnosing this. When you create the patch for that, will you link to it here? I'm interested in seeing where that happens. Thanks!