Spreading object breaks optional enum

[leoselig]

The following very simple snippet shows an error which, I am very certain, is wrong.
When fiddling with it a bit, it seems to be related to 2 conditions:

• the type of field allowing null, hence being an optional
• the state (that should have a valid field) being spread into the return value

https://flow.org/try/#0PTAEAEDMBsHsHcBQiAuBPADgU1AZRQIYpYAqmOAvKAN6KiiQCWW0AJgFygDkAogHIBVALIB9AGoBBADICeXUAB9QAOwCu0aIgC+AbmRYAHhlgAnFKFZZIBdecirlAYxSNYyhrFgAKOqADOhMSc+ESk5IgAlDS+JlgoqibutPT0TCwcKurQADS+9AB0hQGhoCCgsQC2sABuOCgAFox+oATKrP5YOMqwoFgmJqZ+vrraiEA

I ran into this when writing a new redux reducer (though I did not understand yet why this never happened before).

Tested on Flow Try on master, 0.53.1, 0.53.0, 0.52.0, 0.51.1, 0.51.0

[asolove]

I tend to agree I would expect this to work. If you need a workaround right away, this small change is ugly but makes everything work as expected.

I'm also curious why you would set a value for a field in the same object where you then spread in an object that will definitely override the value for that field. I'm sure there is some larger context to the real code, so if you share that maybe we can find a solution.

[leoselig]

@asolove
Your curiosity...

why you would set a value for a field in the same object where you then spread in an object that will definitely override the value for that field

actually answered mine...

though I did not understand yet why this never happened before

I indeed did not mean to spread this way and fixing the order fixes the issue for me

Anyway, I strongly believe there is a defect and this is ONE bug it might trigger

[asolove]

Yeah, could be: if you find another case let us know!

[leoselig]

@asolove Long time no... read
So I hit another use case – this time my workaround does not make sense for me

See this example: https://flow.org/try/#0PTAEAEDMBsHsHcBQiAuBPADgU1AWSwM4ECGA5lgCqY4C8oA3oqKALaEnkBcoBKATgEsAdqQA0THgGNY2bgH5egkYgC+AbmRYAHhlh8UoSAFchklANhDQkvlmIos+ImSwAxYgOgEAFPVAA6QNgANyw+QQATHBVuABIAZQALYmwAHicOSmoAPgBKbgyXKmwGCVsUIz4rRmZmNmcuUAAiSGIAaxx6zKbxWqkZLG4hI2hoXtrA-xCwyKwJdVVNHT0DY1NzS2tbe0d2FwB1PTafP0np8IEo0BjQBOS0wvJirDyCvafqUuZyyuqJOveg2arQ6rEBPX+-VkoGGo3mGhUiCAA

As you can see, as opposed to my initial example, I now really want to spread last, not first, since I am overriding the values

[villesau]

I think this fixes the issue: #7298

[nmote]

This no longer errors in master