introduce $$rest

[tanhauhau]

Fixes #2930

Based on @Conduitry's comment #3015 (comment)

[Conduitry]

Is there a particular reason to freeze this when $$props isn't frozen?

[tanhauhau]

I just think that $$rest shouldn't be mutated, because it's kind of derived from $$props, and mutation on $$rest will not propagate back to the $$props

[Conduitry]

It doesn't have to be ironed out before this can get merged, but what are your thoughts on allowing $$props to be mutated? I think that right now it can but those changes won't be reflected in the corresponding other variables.

[tanhauhau]

Actually, initially I was thinking of only freezing in dev mode, to educate users not to mutate it.

Not sure Object.freeze has any performance penalties...

What do u think?

[tanhauhau]

On another thought, I remove the freeze for now, to be consistent with the $$props.

In a separate PR, I'll add warnings for assignment or mutation on $$props and $$rest

[Conduitry]

We currently disable the dev-mode 'component was created with unknown prop foo' warning when a component uses $$props and I think we should probably do the same when it uses $$rest.

[Conduitry]

I see in #2930 that $$attrs was suggested because it sounds like the name of something in Vue. I don't think that having the same name as Vue for a somewhat similar feature is necessarily a good idea. I'm not married to $$rest either though.

[tanhauhau]

I'm not familiar with vue, but reading their docs on $attr, https://vuejs.org/v2/guide/components-props.html#Disabling-Attribute-Inheritance, it is not exactly the same concept of what we have..

Naming is hard, that's why I just use whatever you suggested...

Maybe some other suggestions:

• $$unknownProps
• $$restProps

Since it's a local variable, I reckon it's minifyable, long names should be fine.

[Conduitry]

Merged, thank you! I've removed the tutorial page for now because if we're going to mention $$restProps in the tutorial we should probably also mention $$props, and if we're mentioning both, maybe they should be on the same page, or at least one should build on the other.

[jimmywarting]

Wow, this is weird stuff... just came to know about this throught some google search.
perks of learning a new framework