Here's an example from a `redactions.scm` file for JSON:

```scheme
(pair value: (number) @redact)
(pair value: (string) @redact)
(array (number) @redact)
(array (string) @redact)
```

This query marks number and string values in key-value pairs and arrays for redaction.

| Capture | Description                    |
| ------- | ------------------------------ |
| @redact | Captures values to be redacted |

### Runnable code detection

The `runnables.scm` file defines rules for detecting runnable code.

Here's an example from an `runnables.scm` file for JSON:

```scheme
(
    (document
        (object
            (pair
                key: (string
                    (string_content) @_name
                    (#eq? @_name "scripts")
                )
                value: (object
                    (pair
                        key: (string (string_content) @run @script)
                    )
                )
            )
        )
    )
    (#set! tag package-script)
    (#set! tag composer-script)
)
```

This query detects runnable scripts in package.json and composer.json files.

The `@run` capture specifies where the run button should appear in the editor. Other captures, except those prefixed with an underscore, are exposed as environment variables with a prefix of `ZED_CUSTOM_$(capture_name)` when running the code.

| Capture | Description                                            |
| ------- | ------------------------------------------------------ |
| @\_name | Captures the "scripts" key                             |
| @run    | Captures the script name                               |
| @script | Also captures the script name (for different purposes) |

<!--
TBD: `#set! tag`
-->

## Language Servers

Zed uses the [Language Server Protocol](https://microsoft.github.io/language-server-protocol/) to provide advanced language support.

An extension may provide any number of language servers. To provide a language server from your extension, add an entry to your `extension.toml` with the name of your language server and the language(s) it applies to:

```toml
[language_servers.my-language]
name = "My Language LSP"
languages = ["My Language"]
```

Then, in the Rust code for your extension, implement the `language_server_command` method on your extension:

```rust
impl zed::Extension for MyExtension {
    fn language_server_command(
        &mut self,
        language_server_id: &LanguageServerId,
        worktree: &zed::Worktree,
    ) -> Result<zed::Command> {
        Ok(zed::Command {
            command: get_path_to_language_server_executable()?,
            args: get_args_for_language_server()?,
            env: get_env_for_language_server()?,
        })
    }
}
```

You can customize the handling of the language server using several optional methods in the `Extension` trait. For example, you can control how completions are styled using the `label_for_completion` method. For a complete list of methods, see the [API docs for the Zed extension API](https://docs.rs/zed_extension_api).