Require instantiable components to extend React.Component

[sophiebits]

Fixes #4599.

[sophiebits]

This almost works, except MockedComponent here doesn't end up with the flag:

react/src/renderers/shared/reconciler/__tests__/ReactMockedComponent-test.js

Line 53 in 2f96d70

MockedComponent = mocks.generateFromMetadata(metaData);

@sebmarkbage ideas?

[sebmarkbage]

If you use an object, jest will mock it. You would potentially set it to an object during DEV or testing maybe?

[sophiebits]

Fixed by changing isReactClass to not have an underscore…

https://github.com/facebook/jest/blob/9d726ed478ecff19acc5bf04a2600e559818cfb6/src/lib/moduleMocker.js#L311

[sebmarkbage]

Another thing we could do is:

element.type.prototype instanceof React.Component

That locks it into a by-reference equality (and therefore a single react package). Not sure if that is good or bad. Certainly more idiomatic.

[syranide]

That locks it into a by-reference equality (and therefore a single react package). Not sure if that is good or bad. Certainly more idiomatic.

Multiple React packages means it's likely they'll be different versions, so that's probably preferable? Mixing React packages seems like a bad idea (or a mistake) and being slapped with an error seems beneficial I would think.

[jimfb]

I like instanceof; feels cleaner than checking for magic properties.

[sophiebits]

I thought the whole point (one of the whole points) of 0.14 (0.15 maybe) was that you can use more than one React.

[syranide]

@spicyj But not mixing between them I would assume?

[jimfb]

@spicyj You can use more than one react-renderer without using more than one react-core. React.Component lives in the shared core, and I think it's very reasonable to assume a single shared react-core.