⚛️Add idx in babel-preset

[pierr]

Idx is the existential function, it seems to me that it would be a benefit for almost all project using react and data in a graph.
I concidered using eject to add this feature but maybe this be a good add for the community.

see https://facebook.github.io/react-native/blog/2017/03/13/idx-the-existential-function.html for more informations about it.

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[gaearon]

Let's do it.

[gaearon]

Hmm. Actually I'm concerned that Babel plugin doesn't verify idx comes from an import from idx package. This change could be dangerous if somebody has a function called idx in their code.

Can you please raise an issue about this in idx repo?

[pierr]

Ok i will do this. Thanks for your quick reply.

[pierr]

@gaearon If fact there is no ambiguity, as idx has to be imported and in the project direct dependencies or devDependencies. I add it to react-scripts dev dependencies.

import idx from 'idx'
const props = {user: {friends :[{friends: 1}]}}
idx(props, _ => _.user.friends[0].friends)

Generated

And i have been able to use idx in a map somewhere else

[1,2,4].map((a, idx) => console.log('idx', idx))

[gaearon]

What happens if the user writes

function idx() {
  // my own code
}

var a = idx();

Isn't Babel plugin going to change the function meaning?

[pierr]

Indeed...

[ggregoire]

Isn't it redundant for those who already use Lodash?

var props = { user: { friends: [{ friends: ['yo'] }] } }

_.has(props, 'user.friends[0].friends') // true
_.get(props, 'user.friends[0].friends') // ['yo']

var props = { user: { friends: [] } }

_.has(props, 'user.friends[0].friends') // false
_.get(props, 'user.friends[0].friends') // undefined

[viankakrisna]

@ggregoire thanks for the lodash trick! been using it everywhere now :) I think the use case for idx babel plugin is to transform the function calls to nested ternary checks https://facebook.github.io/react-native/blog/2017/03/13/idx-the-existential-function.html not really sure why we need this though (will it make the bundle larger for deeply nested property access?)

[ericnakagawa]

I'd love to have this functionality! I'm writing a very long list of ternary functions on my own and it is tedious and bug prone!

This helps greatly when dealing with asynchronously loaded data from APIs you don't control/own.

[wtgtybhertgeghgtwtg]

Correct me if I'm wrong, but shouldn't the optional chaining syntax available with babel@7 now that it's in?
babel PR: babel/babel#5813

[gaearon]

We won't enable that proposal unless it advances to 3rd or 4th stages.

[Timer]

Maybe we shouldn't merge this given the Optional Chaining Operator exists?
I imagine it will progress quickly.

[Timer]

I'll close this because there hasn't been much support around it and there's a syntax proposal in the works.

Thanks @pierr!

[gaearon]

I think Optional Chaining was somewhat controversial and wouldn't count on it progressing quickly.

However, this feature seems like a good fit for babel-plugin-macros support we just merged.
So I'd rather see this as a macro in userland.

[kentcdodds]

Hey guess what! There's already a macro for it! https://github.com/dralletje/idx.macro

Woo!

[Timer]

That's seriously awesome @kentcdodds

[kentcdodds]

That said, it does need to upgrade to babel-plugin-macros: dralletje/idx.macro#3 😅 should be a cinch though!