In addition to this, there are several other optional files and directories that can be used to add functionality to a Zed extension. An example directory structure of an extension that provides all capabilities is as follows:

```
my-extension/
  extension.toml
  Cargo.toml
  src/
    lib.rs
  languages/
    my-language/
      config.toml
      highlights.scm
  themes/
    my-theme.json
```

## WebAssembly

Procedural parts of extensions are written in Rust and compiled to WebAssembly. To develop an extension that includes custom code, include a `Cargo.toml` like this:

```toml
[package]
name = "my-extension"
version = "0.0.1"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
zed_extension_api = "0.1.0"
```

Use the latest version of the [`zed_extension_api`](https://crates.io/crates/zed_extension_api) available on crates.io. Make sure it's still [compatible with Zed versions](https://github.com/zed-industries/zed/blob/main/crates/extension_api#compatible-zed-versions) you want to support.

In the `src/lib.rs` file in your Rust crate you will need to define a struct for your extension and implement the `Extension` trait, as well as use the `register_extension!` macro to register your extension:

```rs
use zed_extension_api as zed;

struct MyExtension {
    // ... state
}

impl zed::Extension for MyExtension {
    // ...
}

zed::register_extension!(MyExtension);
```

## Publishing your extension

To publish an extension, open a PR to [the `zed-industries/extensions` repo](https://github.com/zed-industries/extensions).

> Note: It is very helpful if you fork the `zed-industries/extensions` repo to a personal GitHub account instead of a GitHub organization, as this allows Zed staff to push any needed changes to your PR to expedite the publishing process.

In your PR, do the following:

1. Add your extension as a Git submodule within the `extensions/` directory

```sh
git submodule add https://github.com/your-username/foobar-zed.git extensions/foobar
git add extensions/foobar
```

2. Add a new entry to the top-level `extensions.toml` file containing your extension:

```toml
[my-extension]
submodule = "extensions/my-extension"
version = "0.0.1"
```

> If your extension is in a subdirectory within the submodule you can use the `path` field to point to where the extension resides.

3. Run `pnpm sort-extensions` to ensure `extensions.toml` and `.gitmodules` are sorted

Once your PR is merged, the extension will be packaged and published to the Zed extension registry.

> Extension IDs and names should not contain `zed` or `Zed`, since they are all Zed extensions.

## Updating an extension

To update an extension, open a PR to [the `zed-industries/extensions` repo](https://github.com/zed-industries/extensions).

In your PR do the following:

1. Update the extension's submodule to the commit of the new version.
2. Update the `version` field for the extension in `extensions.toml`
   - Make sure the `version` matches the one set in `extension.toml` at the particular commit.

If you'd like to automate this process, there is a [community GitHub Action](https://github.com/huacnlee/zed-extension-action) you can use.