Handlers

All LSP requests and notifications must be registered before calling main_loop.

Handlers are registered using the RequestRegistry and NotificationRegistry structs. Both store handlers in internal HashMaps, using the method name as the key. When a request or notification is received, the corresponding handler is looked up and invoked based on the method name.

Handler callbacks receive two parameters:

• session: The global state of the server.
• parameters: The request or notification parameters.

Both registries implement Default, but require a salsa::Database type parameter.

Adding Handlers

The RequestRegistry and NotificationRegistry structs provide two methods to register a handler:

• .on: Executes the handler in a separate thread. This is cancelable.
• .on_mut: Executes the handler synchronously with mutable access to the session.

use capabilities::handle_document_symbols;
use capabilities::handle_folding_ranges;
use capabilities::handle_watched_files;
use auto_lsp::lsp_types::notification::DidOpenTextDocument;
use auto_lsp::lsp_types::request::{DocumentSymbolRequest, FoldingRangeRequest};
use auto_lsp::server::{NotificationRegistry, RequestRegistry};

fn main() -> Result<(), Box<dyn Error + Sync + Send>> {
    /* ... */

    let mut request_registry = RequestRegistry::<BaseDb>::default();
    let mut notification_registry = NotificationRegistry::<BaseDb>::default();

    request_registry
        // read only, will be executed in a separate thread
        .on::<DocumentSymbolRequest, _>(handle_document_symbols)
        .on::<FoldingRangeRequest, _>(handle_folding_ranges);

    notification_registry
        // mutable because we need to update the database
        .on_mut::<DidChangeWatchedFiles, _>(handle_watched_files);

    /* ... */
}

Custom Request

You can define your own request types by implementing the Request trait from lsp_types.

pub struct GetWorkspaceFilesUris {}

impl Request for GetWorkspaceFilesUris {
    type Params = (); // Parameters for the request
    type Result = Vec<String>; // Expected response type
    const METHOD: &'static str = "custom/GetWorkspaceFilesUris"; // Method name used in the request
}

Similarly, to define a custom notification, implement the Notification trait instead of Request.

Default Handlers

The default crates provides handlers for several LSP requests and notifications.

changed_watched_files

This notification is handled by the changed_watched_files function in the default crate. It updates files in the workspace when external changes are detected.

To enable this handler, use the WORKSPACE_PROVIDER constant when configuring the server capabilities.

open_text_document

This notification is handled by the open_text_document function in the default module. It ensures that the file is added to the workspace if not already present.

To enable this handler, use the TEXT_DOCUMENT_SYNC constant during server capabilities configuration.