UNSAFE_ lifecycle functions can no longer be defined more than once via mixins

[alibosworth]

Do you want to request a feature or report a bug?

Bug

What is the current behavior?

The unsafe lifecycle function aliases in 16.3.2 are not merged when defined more than once because of mixins, triggering an error:

Uncaught Error: ReactClassInterface: You are attempting to define UNSAFE_componentWillReceiveProps on your component more than once. This conflict may be due to a mixin.

To reproduce: rename all cWM, cWRP, and cWU functions with their UNSAFE_ versions in a project where mixins cause those functions to be duplicated

What is the expected behavior?

That these lifecyle function continue to work as expected when called via UNSAFE aliases in 16.3, and if they are not supposed to with regard to redefining/merging, that the migration path documentation is updated to indicate so.

[gaearon]

Yeah I think we should be merging those.

@bvaughn @acdlite Do you recall if there was any reason we didn't do it? I vaguely remember some discussion about this but I might be confusing it with something else.

[bvaughn]

Which version of create-react-class are you using? I thought I'd fixed this with PR #12036 and version 15.6.3

[bvaughn]

Sorry. Maybe I'm misunderstanding what's being reported! If so, my apologies. A little more context would be helpful.

[alibosworth]

Ah shoot! Yeah somehow we were behind on create-react-class. That makes sense, I thought it was odd I couldn't find anyone else who had hit this. Thanks and sorry for the trouble!

[bvaughn]

No problem! Glad to hear that's all it was 😄