Describing specific Errors in Fin

[legokangpalla]

Hello, first day, kinda getting used to this.

From what I understand of Error class, it seems like it was built for composition. Question arises for me when I want to "describe" a particular function will give certain error, like:

   public record ValidationError(IReadOnlyList<string> FieldPath, BaseType FieldType, string Message);
   ...
   using ValidatorFailure = OneOf<ValidationError, ReadError, OtherError>;

But since Fin<T> have fixed error of type Error, I can't really add the type of error that this function will return explicitly.

So the question is what is best practice in LanguageExt-friendly way? Is specifying error types in return signature not recommended? I was planning to describe error types when possible.

Or am I just opt to use Either? I didn't even consider Result since that seems deprecated going forward.

Also, what would be main reasoning behind fixing error type in Fin? Coming from C++ background, my understanding is Fin is kinda like std::expected. Does Error type hold some kind of special meaning somewhere?

[aloslider]

There are Exceptional and Expected types deriving from Error that you can catch using Fallible trait: #1342
Some old but still relevant description of Error type:#1074
Example:#1400 (comment)

[legokangpalla]

Thanks, doc on Error was what I needed.
And just to reaffirm, fixing function or functors to return specific error type is not a thing right?

[aloslider]

I think its not, but I may miss some context

[louthy]

@legokangpalla I have spent the past two days writing up everything I can think of regarding 'how to handle errors in a functional-way'. It's not quite finished yet and it's very much a 'brain dump', so might not always be coherent! :D

I will finish it over the next week, but in the meantime, it should give you some insights into the full error-handling story.

I hope that helps.