Infered types (`_`) in `#[ts(as = "...")]` by escritorio-gustavo · Pull Request #299 · Aleph-Alpha/ts-rs

escritorio-gustavo · 2024-04-08T12:10:50Z

Goal

This PR aims to allow the use of infered types (_) inside the #[ts(as = "...")] attribute. The _ type will be interpreted as the field's original type. E.g.:

#[derive(TS)]
struct Foo {
    #[ts(as = "Option<_>"]
    bar: i32,
}

is the same as:

#[derive(TS)]
struct Foo {
    #[ts(as = "Option<i32>"]
    bar: i32,
}

but without having to repeat the original type.

This allows us to somewhat support using #[ts(optional)] with any type, by using #[ts(as = "Option<_>", optional)] without requiring us to change the semantics of #[ts(optional)]

Changes

Added a recursive function to traverse the provided type and replace Type::Infer(_) with the field's original type

Checklist

I have followed the steps listed in the Contributing guide.
If necessary, I have added documentation related to the changes made.
I have added or updated the tests related to the changes made.

NyxCode · 2024-04-08T21:36:36Z

Interesting! So _ refers to the original type, right?

NyxCode · 2024-04-08T21:39:17Z

I do think this is pretty neat, though I think it might be a bit unintuitive for anyone who doesn't know what _ does in that context.
Have you considered a different syntax, e.g #[ts(as = "Option<type>")]. I feel like we might be able to come up with something more intuitive, but I'm not sure if the extra effort/complexity involved in parsing this would be worth it.

If the syntax was #[ts(as = "Option<$type>")], we might be able to just string-replace $type with the actual type before parsing it into a syn::Type. Pretty hacky, though.

gustavo-shigueo · 2024-04-09T00:31:18Z

Interesting! So _ refers to the original type, right?

Yes, this is mostly a way to resolve the discussion in #175

gustavo-shigueo · 2024-04-09T00:39:09Z

I do think this is pretty neat, though I think it might be a bit unintuitive for anyone who doesn't know what _ does in that context. Have you considered a different syntax, e.g #[ts(as = "Option<type>")]. I feel like we might be able to come up with something more intuitive, but I'm not sure if the extra effort/complexity involved in parsing this would be worth it.

Both of these would require some heavy refactoring, because as expects valid syntax for a type. Option<type> isn't a valid type because type is a keyword and any syntax we come up with (like Option<$type>) is not gonna be valid either.

Type::Infer(_) is the only thing I could think of that both:

Would previously be a compiler error before this PR (type annotations required ... can't infer type)
Is a valid type that syn can parse

If the syntax was #[ts(as = "Option<$type>")], we might be able to just string-replace $type with the actual type before parsing it into a syn::Type. Pretty hacky, though.

We could make a parse_type function like:

fn parse_type(input: ParseStream) -> Result<Type> {
    let str = parse_assign_str(input)?;
    syn::parse_str(&str.replace("$type", "_"))
}

but since this function wouldn't have access to the original_type the parser implemented in this PR would have to stay, and this function's job would be to replace our custom syntax with _

abhay-agarwal · 2024-04-09T19:35:16Z

I think the understore is super intuitive, as it's already widely used throughout rust syntax. So the code is instantly readable. The other nice thing is that you could, for example, turn a type into a vector, such as as = Vec<_>, or as = Result<_,Something>, etc.

escritorio-gustavo · 2024-04-10T12:10:28Z

There is also precedent for this behavior in serde_with https://github.com/jonasbb/serde_with?tab=readme-ov-file#examples

Annotate your struct or enum to enable the custom de/serializer. The #[serde_as] attribute must be placed before the #[derive].

The as is analogous to the with attribute of serde. You mirror the type structure of the field you want to de/serialize. You can specify converters for the inner types of a field, e.g., Vec<DisplayFromStr>. The default de/serialization behavior can be restored by using _ as a placeholder, e.g., BTreeMap<_, DisplayFromStr>.

NyxCode · 2024-04-10T12:24:16Z

Oh, alright! Maybe it's just me then.
I feel like the semantics of _ are very different here, but I think you two convinced me!

NyxCode · 2024-04-10T12:30:29Z

    }
 }
+
+pub(super) fn type_as_infer(type_as: &Type, original_type: &Type) -> Type {


This is perfectly fine, but just an idea: Would changing the signature to type_as_infer(type_as: &Type, original: &mut Type) -> () make the impl cleaner? I think that might get rid of the parse_quote! calls.

We can't mutate original_type because deeper recursive calls into type_as_infer require the original, unaltered type

I've put something together in #305 to highlight what I had in mind. I've put the &mut on the wrong argument in the snippet above, i think that caused some confusion. Sorry about that.

I've put something together in #305 to highlight what I had in mind.

Oh, that makes a lot more sense! I'll merge that in real quick

NyxCode · 2024-04-10T15:08:25Z

+                    let ty = match field_attr.type_override {
+                        Some(type_override) => quote!(#type_override),
+                        None => {
+                            let ty = field_attr.type_as(&field.ty);


I love how this got a lot simpler. Awesome.

NyxCode

Awesome stuff, great work!

NyxCode · 2024-04-10T15:25:20Z

Also, you were spot on with your take in #175. This solution keeps #[ts(optional)] as it was. Specifically, #[ts(optional)] still doesn't alter the type, just how it's represented. This seems super clean to me!

NyxCode · 2024-04-10T16:03:29Z

Interestingly, this kinda makes #[ts(optional = nullable)] obsolete. It'd be equivalent to

#[ts(as = "Option<_>", optional)]
field: Option<i32>,

escritorio-gustavo · 2024-04-10T17:07:34Z

Interestingly, this kinda makes #[ts(optional = nullable)] obsolete. It'd be equivalent to
#[ts(as = "Option<_>", optional)]
field: Option<i32>,

I just hope no one is crazy enough to do that 😆

escritorio-gustavo added 3 commits April 4, 2024 15:25

Infer type in as attribute

6d23517

Make type parsing more robust

89196a4

Remove todo and fix test

d4fb6e8

escritorio-gustavo mentioned this pull request Apr 8, 2024

Optional fields with #[serde(default)] for deserialization #175

Closed

escritorio-gustavo requested a review from NyxCode April 8, 2024 12:14

escritorio-gustavo mentioned this pull request Apr 8, 2024

Can we support #[serde(with = "..")]? #275

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NyxCode reviewed Apr 10, 2024

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escritorio-gustavo and others added 6 commits April 10, 2024 10:01

Parse infered as in enum fields

a75928e

Make FieldAttr::type_as private

c85f34f

Merge branch 'main' into infer_as

7f754ba

Remove irrelevant attributes from test

dbd27c7

change function to take in &mut Type (#305)

9874a67

make replace_underscore private, move to attr/field.rs

15e9212

NyxCode reviewed Apr 10, 2024

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NyxCode added 2 commits April 10, 2024 17:14

update CHANGELOG.md

0cb2773

add docs

62ffd53

NyxCode approved these changes Apr 10, 2024

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escritorio-gustavo merged commit e671a7a into main Apr 10, 2024

escritorio-gustavo deleted the infer_as branch April 10, 2024 17:07

escritorio-gustavo mentioned this pull request Apr 18, 2024

Fix missing case in #299 #310

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escritorio-gustavo commented Apr 8, 2024 •

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gustavo-shigueo commented Apr 9, 2024 •

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