Allow pathTo and parse to work with Maybe (Id record)

[amitaibu]

fixes #1671

• Fix render link
• Fix parse route
• Tests

[amitaibu]

@mpscholten I've got the tests red, which is good - as I haven't fixed the route parsing yet 😅 . Can you please point me in the right direction for the parsing part

[amitaibu]

I suspect it's here. Looks scary! 😨

[amitaibu]

So if I understand the code correctly, if we wanted to return a Just [here] we'd have to do (

ihp/IHP/RouterSupport.hs

Line 288 in 1c8756d

Just uuid -> uuid |> unsafeCoerce |> Right

)

- Just uuid -> uuid |> unsafeCoerce |> Right
+ Just uuid -> Just uuid |> unsafeCoerce |> Right

But we can't know when it's a Maybe and when a regular. So one option would be keeping the Just in the URL, and parse that. So this URL will be valid NewThing?redirect=Just03142938-62d5-4de1-af90-49726ca98f35 (note the Just in the query param)

[amitaibu]

@mpscholten Is there a way to debug such a function and have it print the value of queryValue ?

[amitaibu]

Well, I've just fixed it "Just" not "Just ". But still would be nice to know if there's a way to debug

[amitaibu]

@mpscholten It's indeed a tricky problem. Is there a way to debug/print the values in those functions?

[mpscholten]

Check out https://hackage.haskell.org/package/base-4.18.0.0/docs/Debug-Trace.html#v:trace

[amitaibu]

After fiddling with the parser, I think it would be easier to keep the Just prefix and Nothing in the URL.

Just	Nothing
http://localhost:8000/NewThing?redirect=Justbbc7604b-09bd-4ce5-a0e4-92409d1de4d9	http://localhost:8000/NewThing?redirect=Nothing

Tests are passing now 😄

[mpscholten]

This implementation is inconsistent with how other Maybe types are working with AutoRoute. E.g. when I have a field myField :: Maybe Int, and I request /MyAction?myField= it will set myField = Nothing, and /MyAction?myField=1337 means Just 1337.

This part of IHP is a bit tricky as you've seen already :D But there's likely a way we get this consistent with the other Maybe implementations

[amitaibu]

I was looking at the code some more, but I don't know how to proceed.

Maybe I'm completely off, but I remember reading somewhere that in the past there was Generic that was added to data which was removed due to long comiple time. Could that be useful in our case, by adding it to to the data FooController ? Maybe with the GHC v9 we're using it would be quicker?

In short, I'm happy I was able to tackle it up to this point, but will need help/ someone to take it from here ✌️

[mpscholten]

Yeah, this is a tricky problem. I've already tried it myself yesterday and couldn't find a quick solution so far. Will take a deeper look soon

[amitaibu]

I just hit this one when implementing a Chat (with ihp openAI) on my app. Tried:

AiChatsAction { maybeAiChatId :: !(Maybe (Id AiChat)) }

Since it's not currently working, as a workaround I can change this to :

AiChatsAction { AiChatId :: !(Id AiChat) } and pass an empty UUID 0000-0000-... (doing that with (newRecord @AiChat).id). But it's not great.

[amitaibu]

as a workaround I can change this to :

Actually, I don't need a workaround (or this feature). I can simply go with

= AiChatsAction
| NewAiChatAction

So I guess this feature is still needed from time to time, but likely there are workarounds.

[mpscholten]

I run into this problem as well every once in a while. Hope we can fix this at some point 👍 I usually follow the same workaround

[CSchank]

Just ran into this - I ended up converting everything in actions to be Maybe Text and then I converted back to UUIDs from there in the actions. A part of my Haskell soul died in doing so. But it works as expected, in terms of not including the parameters if they're Nothing. I wonder, if it can be done for Text, why can't it be done for UUIDs and other things? Shouldn't it work in the same way for all Maybe types, regardless of the type parameter?

[mpscholten]

Shouldn't it work in the same way for all Maybe types, regardless of the type parameter?

Yes. The current implementation of AutoRoute doesn't allow for it. It likely needs an internal refactoring to fix this issue