tslink

tslink represents Rust types as TypeScript types. It helps to create the npm package (based on node module) with all necessary definitions and types.

Table of Contents

1. How it can be useful
2. Building
3. Output
4. Structs
5. Enums
6. Usage

• Attributes
• Multiple attributes
• Struct to TypeScript class
• Struct/Enum to TypeScript interface
• Async methods/functions
• Callbacks in methods/functions
• Naming methods/fields
• Binding data. Arguments binding.
• Binding data. Result/Errors binding.
• Exception suppression
• Usage with node-bindgen

7. Configuration file
8. QA and Troubleshooting

How it can be useful?

Node modules

If you are developing a node module based on Rust for example using node-bindgen crate, tslink will generate an npm package with all necessary TypeScript definitions. It helps much with the integration of a node module and testing.

Sharing types

If you are developing for example a server part on Rust and have a client part on TypeScript, you might be interested in sharing some types from Rust into TypeScript world. Requests or responses can be represented as TypeScript definitions in *.ts files.

Building

Because tslink produces artifacts, by default any IO operations from tslink side would be skipped. This is because compilation can be triggered by multiple reasons (clippy, rust analyzer, etc) and it gives unpredictable IO operations in the scope of the same files and IO errors as a result. To allow tslink to produce artifacts environment variable TSLINK_BUILD should be used with any positive value (true, 1, on).

export TSLINK_BUILD=true && cargo build

☞ NOTE: tslink only creates a representation of the future node module in JavaScript and TypeScript. To create a native node module a crate node-bindgen can be used.

Output

Based on Rust code tslink generates:

• javascript (*.js) for the npm package (library)
• type definitions file (*.d.ts)
• optionally TypeScript file (*.ts) with interfaces

For example for an npm package tslink generates:

- destination_path
    - lib.d.ts     # TypeScript definition
    - lib.js       # Javascript module representation
    - package.json # NPM package description

Optionally tslink can generate *.ts files. Such files aren't a part of an npm-package and are used just to "share" types between Rust and TypeScript. As soon as *.ts files aren't part of an npm-package a destination path for it should be defined separately.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink(target = "./target/selftests/interfaces/interfaces.ts")]
struct TestingA {
    pub p8: u8,
    pub p16: u16,
    pub p32: u32,
    pub p64: u64,
    pub a64: u64,
}

Will generate ./target/selftests/interfaces/interfaces.ts with:

export interface TestingA {
    p8: number;
    p16: number;
    p32: number;
    p64: number;
    a64: number;
}

Structs

tslint represents struct by default as an interface, but it also can be represented as class. Class representation should be used in case if struct has some methods and methods are propagated into the node module.

If a struct is used as a type definition, better to use an interface representation.

For next Rust code tslink generates *.js and *.d.ts files.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
# use std::collections::HashMap;
#[tslink(class)]
struct StructureA {
    pub p8: u8,
    pub p16: u16,
    pub p32: u32,
    pub p64: u64,
    pub a: (u32, u64),
    pub b: Vec<u64>,
    pub c: HashMap<String, u64>,
    pub s: String,
    pub k: Option<String>,
}

#[tslink]
impl StructureA {
    #[tslink]
    pub fn method_a(&self, abs: u8) -> u8 {
        0
    }
}

Typescript type definition (*.d.ts) representation

export declare class StructureA {
    p8: number;
    p16: number;
    p32: number;
    p64: number;
    a: [number, number];
    b: number[];
    c: { [key: string]: number };
    s: string;
    k: string | null;
    method_a(abs: number): number;
}

Enums

Flat enum will be represented as classic TypeScript enum

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink]
enum FlatEnum {
    One,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Nine,
}

Became in *.d.ts

export enum FlatEnum {
    One,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Nine,
}

But any enum with nested types will be represented as interface on TypeScript side.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink]
enum SomeEnum {
    One,
    Two,
    Three(u8),
    Four(u8, u16, u32),
    Five((String, String)),
    Six(Vec<u8>),
}

Became in *.d.ts

export interface SomeEnum {
    One?: null;
    Two?: null;
    Three?: number;
    Four?: [number, number, number];
    Five?: [string, string];
    Six?: number[];
}

Usage

Attributes

Attribute	Usage	Description	Applied To
class	#[tslink(class)]	Tells tslink create TypeScript class instead interface	struct
ignore	#[tslink(ignore)]	Ignore current struct's field or method	struct method
ignore = "list"	#[tslink(ignore = "field_a; field_b; method_a")]	List of fields/methods, which should be ignored. Can be defined only on struct declaration.	struct
snake_case_naming	#[tslink(snake_case_naming)]	Renames struct's field or method into snake case naming (my_field_a became myFieldA)	struct method, functions
rename = "name"	#[tslink(rename = "newNameOfFieldOrMethod")]	Renames struct's methods or functions into given name	struct method and functions
constructor	#[tslink(constructor)]	Marks current methods as constructor. Indeed can be defined only for method, which returns Self.	struct method returns Self
target = "path"	#[tslink(target = "./path_to/file.ts")]	Tells tslink save TypeScript definitions *.ts / *.d.ts into given file	struct, enum
exception_suppression	#[tslink(exception_suppression)]	By default in case of error method/function throws a JavaScript exception. If "exception_suppression" is used, method/function returns an JavaScript Error instead throwing exceptions	struct methods, functions
result = "json"	#[tslink(result = "json")]	Converts Ok case in Result<T, _> into JSON	struct methods, functions
error = "json"	#[tslink(error = "json")]	Converts Err case in Result<_, E> into JSON	struct methods, functions
fn_arg_name = "ref_to_entity"	#[tslink(data = "MyStruct")]	Binds argument type with struct/type/enum on Rust side	struct methods, functions

Multiple attributes

Multiple attributes can be defined

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink(
    class,
    target = "./target/selftests/interfaces/interfaces.ts; ./target/selftests/interfaces/interfaces.d.ts",
    ignore = "_p8;_p16;_p32"
)]
struct MyStruct {
    pub _p8: u8,
    pub _p16: u16,
    pub _p32: u32,
    pub _p64: u64,
    pub a64: u64,
}

impl MyStruct {
    #[tslink(snake_case_naming, exception_suppression)]
    fn my_method(&self) -> Result<i32, String> {
        Err("test".to_string())
    }
}

#[tslink(snake_case_naming, exception_suppression)]
fn my_function() -> Result<i32, String> {
    Err("test".to_string())
}

Struct to TypeScript class

To reflect struct into TypeScript class #[tslink(class)] should be used, because by default tslink represents struct as interface.

If struct has specific constructor, such method should be marked with #[tslink(constructor)].

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink(class)]
struct MyStruct {
    pub field_a: u8,
}

impl MyStruct {
    #[tslink(constructor)]
    fn new() -> Self {
        Self { field_a: 0 }
    }
    #[tslink]
    fn my_method(&self) -> Result<i32, String> {
        Err("test".to_string())
    }
}

If struct doesn't have fields #[tslink(class)] can be applied to impl directly.

# #[macro_use] extern crate tslink;
# use tslink::tslink;

struct MyStruct { }

#[tslink(class)]
impl MyStruct {
    #[tslink(constructor)]
    fn new() -> Self {
        Self { }
    }
}

☞ NOTE: if your structure has constructor mark this method with #[tslink(constructor)] is obligatory to allow tslink represent construtor in JS reflection.

Struct/Enum to TypeScript interface

To reflect struct or enum into TypeScript interface #[tslink] should be used.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
#[tslink]
struct MyStruct {
    pub field_a: u8,
    pub field_b: u8,
    pub field_c: u8,
}

#[tslink]
enum MyFlatEnum {
    One,
    Two,
    Three,
}

#[tslink]
enum MyEnum {
    One(String),
    Two(i32, i32),
    Three,
}

Note, "flat" enum (MyFlatEnum) will be converted into classic TypeScript enum, but composite enum (MyEnum) will converted into interface.

Async methods/functions

Result of async methods/function will be represented as Promise on TypeScript side.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
struct MyStruct {
}

#[tslink(class)]
impl MyStruct {

    #[tslink]
    async fn my_async_method(&self) -> i32 {
        0
    }
}

Would be represented as

export declare class MyStruct {
    my_async_method(): Promise<number>;
}

☞ NOTE: suppression JS exceptions doesn't make sense with promises and using this attribute will not affect any.

Callbacks in methods/functions

The recommended way to define callback is using generic types.

# #[macro_use] extern crate tslink;
# use tslink::tslink;
struct MyStruct {}

#[tslink(class)]
impl MyStruct {
    #[tslink]
    fn test_a<F: Fn(i32, i32)>(&self, callback: F) {
        callback(1, 2);
    }
}

Would be represented as

export declare class MyStruct {
    testA(callback: (arg0: number, arg1: number) => void): void;
}

Naming methods/fields

TypeScript/JavaScript standard of naming: snake case naming. Some crates like node-bindgen automatically rename fields and methods based on this rule. To fit this behavior tslink should know, which fields/methods should be renamed.

The easiest way would be using #[tslink(snake_case_naming)] on a level of method/field. Or at some very specific use-cases can be used #[tslink(rename = "newNameOfFieldOrMethod")] to give method/field some specific name.

# #[macro_use] extern crate tslink;
# use tslink::tslink;

#[tslink(class, snake_case_naming)]
struct MyStruct {
    field_a: i32,
}

#[tslink(class)]
impl MyStruct {
    #[tslink(snake_case_naming)]
    fn my_method_a(&self) -> i32 {
        0
    }
    #[tslink(rename = "newNameOfMethod")]
    fn my_method_b(&self) -> i32 {
        0
    }
}

Would be represented as

export declare class MyStruct {
    thisIsFieldA: number;
    myMethodA(): number;
    newNameOfMethod(): number;
}

☞ NOTE: #[tslink(rename = "CustomName")] cannot be used for renaming fields, but snake_case_naming can be applied to fields on a top of struct.

Binding data. Arguments binding.

Methods/function arguments types can be bound with some data types on level on Rust with #[tslink(data = "MyStruct")].

#[macro_use] extern crate tslink;
use serde::{Deserialize, Serialize};
use tslink::tslink;

// Define error type for bound method
#[tslink]
#[derive(Serialize, Deserialize)]
struct MyError {
    msg: String,
    code: usize,
}

// Make possible convert serde_json error into our error implementation
impl From<serde_json::Error> for MyError {
    fn from(value: serde_json::Error) -> Self {
        MyError {
            msg: value.to_string(),
            code: 1,
        }
    }
}

#[tslink]
#[derive(Serialize, Deserialize)]
struct MyData {
    pub a: i32,
    pub b: i32,
}

struct MyStruct { }

#[tslink(class)]
impl MyStruct {
    #[tslink(
        my_data = "MyData",
        error = "json",
    )]
    fn get_data(&self, my_data: String) -> Result<i32, MyError> {
        println!("my_data.a = {}", my_data.a);
        println!("my_data.b = {}", my_data.b);
        Ok(my_data.a + my_data.b)
    }}

Will be represented as

export declare class MyStruct {
    getData(my_data: MyData): number;
}

Important

1. tslink converts bound data into JSON string. It requires serde, serde_json as dependencies in your project.
2. Because parsing of JSON string potentially can be done with errors, the method/function should return only Result<T, E>
3. Because serde_json returns serde_json::Error error type of result should be convertable from serde_json::Error.
4. In most cases you would use binding of data with #[tslink(error = "json")] because it allows you to use your implementation of error. And it's a recommended way.
5. In the declaration of the method/function on Rust side, the type of argument should be String (ex: fn get_data(&self, my_data: String) -> Result<MyData, MyError>), but in the body of your method/function this argument will be considered as bounded type.
6. And bound type and error should implement Serialize and Deserialize

Binding data. Result/Errors binding.

To bind error with some of your custom types #[tslink(error = "json")] should be used, like it was shown in "Binding data. Arguments binding.". Like an argument error will be serialized into JSON string on Rust level and parsed from JSON string on TypeScript/JavaScript level.

To bind result with some of your custom data type #[tslink(result = "json")] should be used.

#[macro_use] extern crate tslink;
use serde::{Deserialize, Serialize};
use tslink::tslink;

// Define error type for bound method
#[tslink]
#[derive(Serialize, Deserialize)]
struct MyError {
    msg: String,
    code: usize,
}

// Make possible convert serde_json error into our error implementation
impl From<serde_json::Error> for MyError {
    fn from(value: serde_json::Error) -> Self {
        MyError {
            msg: value.to_string(),
            code: 1,
        }
    }
}

#[tslink]
#[derive(Serialize, Deserialize)]
struct MyData {
    pub a: i32,
    pub b: i32,
    pub c: String,
}

struct MyStruct { }

#[tslink(class)]
impl MyStruct {
    #[tslink(
        my_data = "MyData",
        result = "json",
        error = "json",
    )]
    fn get_data(&self, my_data: String) -> Result<MyData, MyError> {
        Ok(MyData {
            a: my_data.a + 1,
            b: my_data.b + 1,
            c: format!("{}{}", my_data.c, my_data.c),
        })
    }}

Will be represented as

export declare class MyStruct {
    getData(my_data: MyData): MyData;
}

Important

1. tslink converts bound data into JSON string. It requires serde, serde_json as dependencies in your project.
2. Because parsing of JSON string potentially can be done with errors, the method/function should return only Result<T, E>
3. Because serde_json returns serde_json::Error error type of result should be convertable from serde_json::Error.
4. In most cases you would use binding of data with #[tslink(error = "json")] because it allows you to use your implementation of error. And it's a recommended way.
5. In the declaration of the method/function on Rust side, the type of argument should be String (ex: fn get_data(&self, my_data: String) -> Result<MyData, MyError>), but in the body of your method/function this argument will be considered as bounded type.
6. And result type and error should implement Serialize and Deserialize.

Exception suppression

Would be exception thrown or no is up to the library/crate, which is used to create a node module. For example node-bindgen throws exceptions on JavaScript level as soon as a method/function is done with an error. But tslink allows customizing this scenario.

By default exception suppression is off and any error on Rust level became an exception on JavaScript level.

Let's take a look to the previous example:

# #[macro_use] extern crate tslink;
# use serde::{Deserialize, Serialize};
# use tslink::tslink;
# #[tslink]
# #[derive(Serialize, Deserialize)]
# struct MyError {
#     msg: String,
#     code: usize,
# }
# // Make possible convert serde_json error into our error implementation
# impl From<serde_json::Error> for MyError {
#     fn from(value: serde_json::Error) -> Self {
#         MyError {
#             msg: value.to_string(),
#             code: 1,
#         }
#     }
# }
struct MyStruct { }

#[tslink(class)]
impl MyStruct {
    #[tslink(
        error = "json",
    )]
    fn get_data(&self, my_data: String) -> Result<i32, MyError> {
        Err(MyError { msg: "Test".to_string(), code: 1})
    }}

Will be represented as

export declare class MyStruct {
    getData(my_data: MyData): number;
}

Method getData returns MyData but in case of error JavaScript exception will be thrown.

Using #[tslink(exception_suppression)] we can change it.

# #[macro_use] extern crate tslink;
# use serde::{Deserialize, Serialize};
# use tslink::tslink;
# #[tslink]
# #[derive(Serialize, Deserialize)]
# struct MyError {
#     msg: String,
#     code: usize,
# }
# // Make possible convert serde_json error into our error implementation
# impl From<serde_json::Error> for MyError {
#     fn from(value: serde_json::Error) -> Self {
#         MyError {
#             msg: value.to_string(),
#             code: 1,
#         }
#     }
# }
struct MyStruct { }

#[tslink(class)]
impl MyStruct {
    #[tslink(
        error = "json",
        exception_suppression
    )]
    fn get_data(&self, my_data: String) -> Result<i32, MyError> {
        Err(MyError { msg: "Test".to_string(), code: 1})
    }}

Will be represented as

export declare class MyStruct {
    getData(my_data: MyData): number | (Error & { err?: MyError});
}

Now getData returns or number, or Error & { err?: MyError} in case of error, but an exception is suppressed.

Use or not to use this feature is up to the developer, but in general it's a good way to reduce try/catch blocks on JavaScript/TypeScript side and be ready for errors in places where it's potentially possible.

Usage with node-bindgen

node-bindgen crate allows to create native node module and with tslink to get a complete npm project.

There just one rule to common usage - call of #[tslink] should be always above of call #[node_bindgen]

#[macro_use] extern crate tslink;
use tslink::tslink;
use node_bindgen::derive::node_bindgen;

struct MyScruct {}

#[tslink(class)]
#[node_bindgen]
impl MyScruct {
    #[tslink(constructor)]
    #[node_bindgen(constructor)]
    pub fn new() -> Self {
        Self {}
    }

    #[tslink(snake_case_naming)]
    #[node_bindgen]
    fn inc_my_number(&self, a: i32) -> i32 {
        a + 1
    }
}

Please note, node-bindgen by default applies snake case naming to methods. You should use #[tslink(snake_case_naming)] to consider this moment.

By default node-bindgen creates index.node in ./dist folder of your root. In Cargo.toml file should be defined suitable path in section [tslink]:

File: ./Cargo.toml (in a root of project):

[project]
...

[lib]
...

[tslink]
node = "./dist/index.node"

[dependencies]
...

Full example of node-bindgen usage is here. To start it:

git clone https://github.com/icsmw/tslink.git
cd tslink/examples/node_bindgen
sh ./run_test.sh

Configuration

Global configuration of tslink can defined in section [tslink] of Cargo.toml file in the root of your project. It's required in most cases. This settings allows to define a path to a native node module, which will be bound with an npm package.

But if tslink is used only to generate interfaces in *.ts files, a configuration file can be skipped.

Example of ./Cargo.toml with tslink settings:

[package]
name = "tslink-test"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]
path = "rs/lib.rs"

[tslink]
# [required] path to native node module
node = "./dist/index.node"
# [optional] global rule of renaming (can be: "method" or "fields" or both - "methods,fields")
snake_case_naming = "methods"
# [optional] global rule for javascript exception suppression
exception_suppression = true

Field	Required	Values	Description
node = "path_to_native_node_module"	yes	path to file	path to native node module
snake_case_naming = "rule"		"methods", "fields" or "methods,fields"	global rule of renaming
exception_suppression = true		bool	global rule for javascript exception suppression

QA and Troubleshooting

Q: tslink doesn't create any files

A: make sure, the environment variable TSLINK_BUILD has been exported with true or 1

---

Q: rust-analyzer reports IO errors from tslink

A: remove the environment variable TSLINK_BUILD or set it into false or 0

---

Q: what is it ./target/selftests?

A: these are artifacts, which tslink created with cargo test. It's safe to remove.

---

Q: Does tslink create native node module (like index.node)

Q: No, tslink only creates a representation of the future node module in JavaScript and TypeScript. To create a native node module a crate node-bindgen can be used.

---

Q: With node-bindgen I get errors on JavaScript side like "no method_call_b() on undefined".

Q: Note, node-bindgen by default applies snake case naming to methods. You should use #[tslink(snake_case_naming)] to consider this moment.