Added warning to <Context.Provider> in case no value prop is provided

[charlie1404]

Summary

This PR aims to add a fix for #19020

1. There is a duplication in what I have done in files
   • packages/react-reconciler/src/ReactFiberBeginWork.new.js
   • packages/react-reconciler/src/ReactFiberBeginWork.old.js

In feature flag saw const enableNewReconciler = false but still cannot jump to any solid conclusions hence added in both.

Test Added
packages/react-reconciler/src/__tests__/ReactNewContext-test.js test to detect warning.

Tests Updated Reason
As now <Context.Provider> now throws a warning if value prop is not given, and hence updated the ones which were not having value prop to have null now.

Points to be discussed

1. What should be the warning message, (not really good with this) 😅
2. Should this be included in both old and new, or I have added in the totally wrong place.
   • if correct, out of curiosity why there are 2 files, seems almost identical, and only these but a whole lot files are in the same format. (please ignore if very long explanation and out of the scope of this PR)
3. Should any more test cases to be added in this?

cc @brunogonzales @heath-freenome

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[charlie1404]

did like the name of the code sandbox 🤣.
Edit:
code sandbox bot edited the old message

old	new
cocky-margulis-zss43	unruffled-bardeen-vj2s6

wondering why cannot just update deps it old one 😞

[heath-freenome]

Question, would making the value prop .isRequired also accomplish this?

[charlie1404]

Question, would making the value prop .isRequired also accomplish this?

@heath-freenome
Initially gave a thought on that idea, but did not proceed for 2 reasons:

1. If we use prop types there is a possibility that value prop can actually be null or undefined, say if the value is being set from some key in state, which is an object, but the key used is null or undefined for some reason, in that case, it will start adding warnings to console, not sure if we should do that, worth discussing. The 'value' in props only gives a warning if there is no value prop supplied to <Context.Provider>.

2. Now if we use prop types I had to do Object.assign with workInProgress.type.propTypes, but as this is an internal component and had no prop types defined hence was undefined, not sure if I should add a completely new object, ignoring old one or still do Object.assign maybe I was looking at the wrong place.

But pointing to prop types gave me a better message, thanks for that, updating it now.

[eps1lon]

React just recently removed all runtime dependencies to prop-types. It's unlikely they re-introduce it. Especially given prop-types cannot distinguish between a missing prop and an undefined prop which @charlie1404 already pointed out.

[gaearon]

Let's reword this a bit:

The `value` prop is required for the `<Context.Provider>`. Did you misspell it or forget to pass it?

[charlie1404]

Thanks for the message 😅 .

[charlie1404]

updated

[gaearon]

Same

[gaearon]

Make this value={undefined} instead and you won't need to change the message.

[charlie1404]

now using undefined and reverted message

[gaearon]

Small nits and this is good to go.

[gaearon]

Coolio, thanks.