# Contribution Guide

## Setting up your local development environment

### Add the Wasm target

```bash
rustup target add wasm32-unknown-unknown
```

### Install [cargo-make](https://github.com/sagiegurari/cargo-make)

```bash
cargo install cargo-make
```

You can use the following command to list all available tasks for Yew:

```bash
cargo make --list-all-steps
```

The most important tasks are outlined below.

## Tests

To run all tests, use the following command:

```bash
cargo make tests
```

### Browser tests

`cargo make tests` will automatically download Geckodriver to a temporary location if it isn't in the PATH.

Because Geckodriver looks for `firefox` in the path, if you use
FireFox Developer Edition, you may get an error, because Developer Editions
binary is called `firefox-developer-edition`.
To fix this, either install the standard version of Firefox or symlink
`firefox` to `firefox-developer-edition`.

### Fetch service tests

The tests for the fetch service require a local [httpbin](https://httpbin.org/) server.
If you have [Docker](https://www.docker.com/) installed,
`cargo make tests` will automatically run httpbin in a container for you.

Alternatively, you can set the `HTTPBIN_URL` environment variable to the URL you wish to run tests against.

### WebSocket service tests

The tests for the web-socket service require an echo server.
If you have [Docker](https://www.docker.com/) installed,
`cargo make tests` will automatically run an [echo server](https://hub.docker.com/r/jmalloc/echo-server) in a container for you.

Alternatively, you can set the `ECHO_SERVER_URL` environment variable to the URL you wish to run tests against.

### Macro tests

When adding or updating tests, please make sure to update the appropriate `stderr` file, which you can find [here](https://github.com/yewstack/yew/tree/master/packages/yew-macro/tests/macro) for the `html!` macro.
These files ensure that macro compilation errors are correct and easy to understand.
These errors can change with each release of the compiler so they should be generated with the Rust version 1.51 
(because some tests make use of const generics which were stabilized in that version).

To update or generate a new `stderr` file you can run `cargo make test-overwrite` in the `yew-macro` directory.

## Linting

The following command checks the code using Rustfmt and Clippy:

```bash
cargo make lint
```

To automatically fix formatting issues, run `cargo fmt` first.

## Benchmarks

If you wish to improve the performance of Yew, we ask you to prove the improvements of your changes through benchmarking.

Some components of Yew have dedicated benchmarks which can be run with the following command:

```bash
cargo make benchmarks
```

There's also a benchmark for the framework as a whole. Running it is a bit more involved:

1. Fork and clone [yewstack/js-framework-benchmark](https://github.com/yewstack/js-framework-benchmark)
2. Update `frameworks/yew/Cargo.toml` with your fork of Yew and the branch for your changes
3. Open a new PR with your `Cargo.toml` changes

Feel free to add new benchmark tests if the current benchmark coverage is insufficient!

> See #1453 for a discussion on how to make this easier.

## Writing APIs

When building new APIs, think about what it would be like to use them. Would this API cause confusing and hard to pin error mesages? Would this API integrate well with other APIs? Is it intuitive to use this API?

Below, you can find some useful guidance and best practices on how to write APIs. These are only _guidelines_ and while they are helpful and should be followed where possible, in some cases, it may not be possible to do so.

- [The Rust API Guidelines](https://rust-lang.github.io/api-guidelines/)
- [Elegant Library APIs in Rust](https://deterministic.space/elegant-apis-in-rust.html)