[fbonetti]

> Elm's type system will not catch this bug at compile time

This is completely false. Elm's type system will force you to handle the decoding failure at compile time. The `decodeString` function has the following type:

    decodeString : Decoder a -> String -> Result String a

Which means that when you call `decodeString`, it will return a Result containing either the decoded value or a String describing the error.

This is not a "runtime failure". This is the compiler forcing you to explicitly spell out what you want to happen the case of a decoding problem. The difference between Typescript and Elm is that Typescript's compiler will happily let your program crash when this type of issue occurs, whereas Elm's compiler won't.

[hudon]

You're just rewording what I said. The coder can simply ignore that string or make it empty, which can lead to a runtime failure if another module depends on a value being returned (think a runtime failure from a non-exhaustive pattern match). If they were a lazy coder in TypeScript, they'll be lazy in Elm (:

So, no, what I said is not "completely false"

[Exolon]

I would dispute the idea that "if they were a lazy coder in TypeScript, they'll be lazy in Elm". The fact that Elm forces you to at least think for a moment about how handle the failure case is a good thing. Even if you're inclined to take the path of least resistance, as probably most of us programmers are, what does that actually look like?

You have one case branch that looks like:

  GotUserList (Ok userList) -> ...

and another that looks like:

  GotUserList (Err _) -> ...

Since we need to pattern match on both types of the Result structure in our update cycle, there isn't really an opportunity to implicitly gloss over a failure to parse. Of course you can try to make the decoder super permissive, but this is harder than doing it the right way. If you're REALLY lazy, you can throw in "Debug.crash" in the failure case, but there's no general solution for throwing grenades at your foot :D