typescript-definitions
Exports serde-serializable structs and enums to Typescript definitions.
Motivation 🦀
Now that rust 2018 has landed there is no question that people should be using rust to write server applications (what are you thinking!). But generating wasm from rust code to run in the browser is currently much too bleeding edge.
Since javascript will be dominant on the client for the forseeable future there remains the problem of communicating with your javascript from your rust server.
Fundamental to this is to keep the datatypes on either side of the connection (http/websocket) in sync.
Typescript is an incremental typing system for javascript that is as almost(!) as tricked as rust... so why not create a typescript definition library based on your rust code?
Please see Credits.
typescript-definitions
(as of 0.1.7) uses edition=2018
(heh).
example:
// #[cfg(target_arch="wasm32")]
use *;
use Serialize;
use TypescriptDefinition;
Using wasm-bindgen this will output in your *.d.ts
definition file:
export type Enum =
{tag: "V1", fields: { Foo: boolean } }
| {tag: "V2", fields: { Bar: number, Baz: number } }
| {tag: "V3", fields: { Quux: string } }
;
Using typescript-definitions
NB: Please note these macros - by default - work only for the debug build since they pollute the code with strings and methods all of which are proabably not useful in any release (Since you are only using them to extract information about your current types from your code). In release builds they become no-ops. This means that there is no cost to your release exes/libs or to your users by using these macros. Zero cost abstraction indeed. Beautiful.
Also, although you might need nightly to run wasm-bingen
your code can remain stable.
See features below if you really want them in your release build.
There is a very small example in the repository that works for me (TM) if you want to get started on your own.
This crate only exports two derive macros: TypescriptDefinition
and TypeScriptify
, a simple
trait TypeScriptifyTrait
and a (very simple) serializer for byte arrays.
In your crate create a lib target in Cargo.toml
pointing
to your "interfaces"
[]
= "mywasm" # whatever... you decide
= "src/interface.rs"
= ["cdylib"]
[]
= "0.1"
= { = "1.0", = ["derive"] }
[]
= "0.2"
Then you can run (see here if you don't want to go near WASM):
What just happened? This.
Getting the toolchains
If you don't have these tools then see here (You might also need to get rustup first):
or use wasm-pack (the typescript library will be in pkg/mywasm.d.ts
).
|
Using type_script_ify
You can ignore WASM totally by deriving using TypeScriptify
:
// interface.rs
// wasm_bindgen not needed
// use wasm_bindgen::prelude::*;
use Serialize;
use TypeScriptify;
// Then in `main.rs` (say) you can generate your own typescript
// specification using `MyStruct::type_script_ify()`:
// main.rs
// need to pull in trait
use TypeScriptifyTrait;
Use the cfg macro To protect any use of type_script_ify()
if you need to.
If you have a generic struct such as:
use Serialize;
use TypeScriptify;
then you need to choose a concrete type to generate the typescript: Value<i32>::type_script_ify()
. The concrete type
doesn't matter as long as it obeys rust restrictions; the output will still be generic export type Value<T> { value: T }
.
Currently type bounds are discarded in the typescript.
So basically with TypeScriptify
you have to create some binary that, via println!
or similar statements, will
cough up a typescript library file. I guess you have more control here... at the expense of complicating
your Cargo.toml
file and your code.
Features
As we said before typescript-descriptions
macros pollute your code with
static strings and other garbage. Hence, by default, they only work in debug mode.
If you actually want T::type_script_ify()
(for TypeScriptify) available in your
release code then change your Cargo.toml
file to:
[]
= "0.1"
= ["export-typescript"]
## OR
= { ="0.1", =["export-typescript"] }
AFAIK the strings generated by TypescriptDescription don't survive the invocation
of wasm-bindgen
even in debug mode. So your *.wasm files are clean. You still need
to add --features=export-typescript
to generate anything in release mode though.
Serde attributes.
See Serde Docs.
typescript-definitions
tries to adhere to the meaning of serde attributes
like#[serde(tag="type")]
and #[serde(tag="tag", content="fields")]
.
Before 0.1.8 we had an implicit default tag of "kind" for enums. Now we don't
(although we still have a implicit transparent
on NewTypes).
Serde attributes understood
- rename, rename_all:
- tag:
- content:
- skip: (
typescript-definitions
also skips - by default - PhantomData fields ... sorry ghost who walks) - serialize_with="typescript_definitions::as_byte_string"
- transparent: Newtypes are automatically transparent. Structs with a single field can be marked transparent.
serialize_with
, if placed on a [u8]
or Vec<u8>
field, will take
that field to be a string. (And serde_json will output a \xdd
encoded
string of the array. or you can create your own... just ensure to name it as_byte_string
)
use Serialize;
use ;
println!;
prints export type S = { image: string, buffer: number[] };
.
Serde attributes understood but rejected
- flatten (This will produce a panic). Currently on my TODO list.
All others are just ignored.
Problems
Oh yes there are problems...
Currently typescript-descriptions
will not fail (AFAIK) even for
structs and enums with function pointers fn(a:A, b: B) -> C
(generates typescript lambda (a:A, b:B) => C
)
and closures Fn(A,B) -> C
(generates (A,B) => C
). These make no sense in the current
context (data types, json serialization) so this might be considered a bug.
Watchout!
This might change if use cases show that an error would be better.
If you reference another type in a struct e.g.
// #[cfg(target_arch="wasm32")]
use *;
use Serialize;
use ;
then this will "work" (producing export type A = { x: number ,b: B<number> })
) but B will be opaque to
typescript unless B is also #[derive(TypescriptDefinition)]
.
Currently there is no check for this omission.
Also Trait bounds are stripped out for typescript; you can't serialize Traits! However...
If using type_script_ify
then anything other than simple trait bounds will fail to compile. (because
the impl<...> TypeScriptify for T<...> {}
that is automatically generated by typescript-descriptions
will be garbled).
- no
where
clauses. - no generic Traits.
Use WASM
instead.
This might be relaxed in future.
The following types are rendered as:
Option<T>
=>T | null
(can't use undefined because this will mess with object checking)HashMap<K,V>
=>{ [key:K]:V }
(same forBTreeMap
)HashSet<V>
=>V[]
(same forBTreeSet
)&[u8]
andVec<u8>
are expected to be byte buffers but are still rendered asnumber[]
since this is whatserde_json
does. However you can force the output to be a string using#[serde(serialize_with="typescript_defintions::as_byte_string")]
An enum
that is all Unit types such as
is rendered as a typescript enum:
enum Color {
Red = "Red",
Green ="Green",
Blue = "Blue"
}
because serde_json will render Color::Red
as the string "Red"
instead of Color.Red
(because JSON).
TODO: What about enum Color {Red = 0, Green = 1 , Blue= 2}
?
Serde always seems to render Result
(in json) as {"Ok": T } | {"Err": E}
i.e as "External"
so we do too.
Formatting is rubbish and won't pass tslint. This is due to the quote! crate taking control of the output token stream. I don't know what it does with whitespace for example... (is whitespace a token in rust?). Anyhow... this crate applies a few bandaid regex patches to pretty things up.
We are not as clever as serde or the compiler in determining the actual type. For example this won't "work":
use Cow as Pig;
use ;
println!;
gives export type S = { pig : Pig<string> }
instead of export type S = { pig : string }
At a certain point typescript-definitions
just assumes that the token identifier i32
(say)
is really the rust signed 32 bit integer and not some crazy renamed struct in your code!
Complex paths are ignored std::borrow::Cow
and mycrate::mod::Cow
are the same to us. We're
not going to reimplement the compiler to find out if they are actually different. A Cow is
always "Clone on write".
We can't reasonably obey serde attributes like "flatten" since we would need to find the actual Struct object (from somewhere) and query its fields.
TODO
Generate a typescript verifier for each type (maybe). We really need some testing of the typescript types against serde_json.
export verify_A<T>(obj: any): boolean {/*... */ }
// *or*
export verify_A<T>(obj: any): {Ok: A<T>} | {Err: string} {/* ... */}
// *or* using guards https://www.typescriptlang.org/docs/handbook/advanced-types.html
export is_A<T>(obj: any): obj is A<T> { /* ... */ }
or something...
Then one could:
let o : any = JSON.parse(some_string_from_the_inet);
if verify_A<number>(o) {
return o as A<number>
} else {
// err....
}
maybe...
Credits
For intial inspiration see http://timryan.org/2019/01/22/exporting-serde-types-to-typescript.html
Forked from wasm-typescript-definition
by @tcr
which was forked from rust-serde-schema
by @srijs.
type_script_ify
idea from typescriptify
by @n3phtys
Probably some others...
License
MIT or Apache-2.0, at your option.