Uncaught TypeError: Cannot read property 'key' of null

[TrySound]

And again and again and again...

Observed Behaviour

Inferno is...

Uncaught TypeError: Cannot read property 'key' of null
at patchKeyedChildren (patching.js:421)
at patchChildren (patching.js:200)
at patchElement (patching.js:86)
at patch (patching.js:25)
at patchComponent (patching.js:324)
at patch (patching.js:17)
at patchComponent (patching.js:275)
at patch (patching.js:17)
at patchChildren (patching.js:191)
at patchElement (patching.js:86)

Expected Current Behaviour

Inferno should...

Inferno Metadata

macOS / Windowx / Linux
Safari / Chrome / Firefox / ...

[jmhdev]

@TrySound Have you been able to isolate the component that the error is stemming from? Does this occur on intial render, after a setState, or some other event?

[Havunen]

Steps to reproduce missing :(

[TrySound]

Yeah, don't have a time yet. I guess I miss key props somewhere.

[LukeSheard]

Any update on a reproduction?

[pomle]

This seems to happen to me when I .map() over an Immutable.js List.

Error:

const bookings = new List(...);
return <div>
    { bookings.map(b => <span>) }
</div>;

No error:

const bookings = new List(...);
return <div>
    { [...bookings].map(b => <span>) }
</div>;

Attaching error screen from a create-inferno-app project.

[LukeSheard]

@pomle a small reproduction would be very helpful. I think this might be related to #1103 but without a small reproduction this is hard to isolate.

[pomle]

@LukeSheard here ya go: https://github.com/pomle/inferno-key-error-repo

[pomle]

@LukeSheard I think this is the "culprit". It checks if a node is exactly an Array. React supports iterables I believe.

inferno/packages/inferno/src/core/normalization.ts

Line 43 in 2f48730

if (isArray(n)) {

Here's a thread that I think discusses the upgrade of React
facebook/react#2296

[Havunen]

Inferno supports iterables when inferno-compat package is used. This has been like this for long time. I'm closing this as its working as designed.

If we want to bring iterable support into core that is separate discussion and new issue can be created for that.