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$attrs is undefined when component has no props #6263

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greegus opened this issue Aug 1, 2017 · 8 comments
Closed

$attrs is undefined when component has no props #6263

greegus opened this issue Aug 1, 2017 · 8 comments
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@greegus
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@greegus greegus commented Aug 1, 2017

Version

2.4.2

Reproduction link

https://jsfiddle.net/50wL7mdz/50757/

Steps to reproduce

Access $attrs as object within component context, when no props were provided.

What is expected?

$attrs is an object containing unrecognized props. Therefore I would expect an empty object, when no props are specified on component tag.

What is actually happening?

$attrs is undefined

@posva
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@posva posva commented Aug 1, 2017

Out of curiosity, what problem are you facing by having an undefined $attrs? Are you accessing $attrs.something? (if so, why?)

edit: I'm also asking because having $attrs equal undefined when there're no attrs can actually be useful

@nickmessing
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@nickmessing nickmessing commented Aug 1, 2017

@greegus, in case you're doing something like if ($attrs.myProp) you can do if ($attrs?.myProp) by using babel-plugin-transform-optional-chaining.

@LinusBorg
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@LinusBorg LinusBorg commented Aug 2, 2017

I would judge this to be expected behaviour, but it's debatable.

@posva
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@posva posva commented Aug 7, 2017

ping @greegus

@chrisvfritz
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@chrisvfritz chrisvfritz commented Aug 8, 2017

Just ran into this and it was definitely unexpected for me that $attrs should ever be undefined.

For example, if you were writing a todo app that starts out with no todos, it would be very strange to make the list begin as undefined instead of []. You'd have to add if statements (or optional chaining) all over your app. This case is similar.

For niche cases when a user wants to check if any $attrs exist, it'd still be possible to use Object.keys($attrs).length, so that case is still covered.

The part that really convinces me this is a bug though, is that $attrs is set to an empty object when a prop is passed to a component - as the OP points out. So currently, really checking if any $attrs exist would require both strategies:

$attrs && Object.keys($attrs).length
@LinusBorg
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@LinusBorg LinusBorg commented Aug 8, 2017

@chrisvfritz convinced me - it's a bug.

@LinusBorg LinusBorg added bug and removed discussion labels Aug 8, 2017
@zxc0328
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@zxc0328 zxc0328 commented Aug 24, 2017

@LinusBorg Looks like no one is working on this bug currently. May I have a pr for this?

@LinusBorg
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@LinusBorg LinusBorg commented Aug 24, 2017

Sure!

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6 participants