Expand decode error to include information about error

[hellos3b]

Would be nice if the decode exception included information about the error instead of the error message, so the output could be formatted nicely to an end user

type path = array<string>
type expected = string
type actual = string

exception DecodeError(path, expected, actual)

The path property can point to where in an object or array that the error occured, so I can log a message like Expected "string" in Object.nested.field[0]

[glennsl]

It's certainly possible to make the errors more strongly typed, but this scheme doesn't cover all the cases. How would you, for example, use this in oneOf.

It would also be a major breaking change. And I'm not sure how useful it really is, seeing as your use case of logging a string seems to be covered well by the current error representation.

But I'm open to suggestions and use cases that show its usefulness.

[DZakh]

In ReScript struct, it's represented as an InvalidUnion error code. Used the feature mostly for tooling, not in application code, e.g. to add custom error handling for specific parsing errors https://github.com/DZakh/rescript-stdlib-vendorer/blob/99fd057478c5d2596b6de48a0b26ad376808304b/src/interactors/RunCli.res#L48-L74.
Not sure whether it's a use case for rescript-json-combinators though.