[acemarke]

Yeah, Dan's pointed out a number of times that even with FP and immutability, _local_ mutation is fine. After all, the mechanism for immutable updates is to make copies of the original data, and then mutate / overwrite pieces of the copies.

Immer just does that in a really slick way.

My only concern for using Immer by default in RTK is the potential that someone would learn Redux by osmosis through looking at a codebase where every reducer is doing `state.someField = someValue`, think that actual mutation _is_ the right way to use Redux, and then try to do the same thing in another project and actually mutate data for real.

I can't prevent that, so my only answer was to repeatedly emphasize in this new tutorial that you _must_ do immutable updates, and that you can _only_ "mutate" inside of RTK's APIs thanks to Immer:

- https://redux.js.org/tutorials/essentials/part-2-app-structu...

- https://redux.js.org/tutorials/essentials/part-3-data-flow#s...

But yeah, the massive improvements in code size and readability are more than sufficient to justify the small potential downside there.