[fix] make errors in Action less restrictive

[dummdidumm]

Part of #6015

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[benmccann]

I think we added some type tests somewhere? Should we try to cover this with them?

[dummdidumm]

@Rich-Harris removed them 😄 they were related to the JSONObject thing which we removed entirely. Such a simple change doesn't warrant a type test IMO.

[benmccann]

Can the type really be any? I'd think it'd have to be something JSON serializable at least?

Ah, that's why I didn't know where they were anymore 😄 All types are conceptually simple, but we're always making small mistakes where we get things wrong. A test would prevent a regression and clarify how non JSON serializable objects should be treated

[dummdidumm]

It has to be, yes, but it's impossible to type "this expects a JSON type", see #5974 for more info

[benmccann]

For others, following that link, I found the explanation here: #5963 (comment)

I wonder if we should at least do something like:

export type JSONSerializable = any

...

errors: Record<string, JSONSerializable>

It doesn't change what's allowed but may help to document what's expected to clarify things for users

[Rich-Harris]

Tried it just now, it doesn't work. TypeScript replaces it with the underlying value