[ty] Implemented partial support for "find references" language server feature. (#19475)

This PR adds basic support for the "find all references" language server feature.

---------

Co-authored-by: UnboundVariable <unbound@gmail.com>

crates/ty_server/src/server.rs

@@ -209,6 +209,7 @@ impl Server {
             type_definition_provider: Some(TypeDefinitionProviderCapability::Simple(true)),
             definition_provider: Some(lsp_types::OneOf::Left(true)),
             declaration_provider: Some(DeclarationCapability::Simple(true)),
+            references_provider: Some(lsp_types::OneOf::Left(true)),
             hover_provider: Some(HoverProviderCapability::Simple(true)),
             signature_help_provider: Some(SignatureHelpOptions {
                 trigger_characters: Some(vec!["(".to_string(), ",".to_string()]),

crates/ty_server/src/server/api.rs

@@ -56,6 +56,9 @@ pub(super) fn request(req: server::Request) -> Task {
         requests::HoverRequestHandler::METHOD => background_document_request_task::<
             requests::HoverRequestHandler,
         >(req, BackgroundSchedule::Worker),
+        requests::ReferencesRequestHandler::METHOD => background_document_request_task::<
+            requests::ReferencesRequestHandler,
+        >(req, BackgroundSchedule::Worker),
         requests::InlayHintRequestHandler::METHOD => background_document_request_task::<
             requests::InlayHintRequestHandler,
         >(req, BackgroundSchedule::Worker),

crates/ty_server/src/server/api/requests.rs

@@ -5,6 +5,7 @@ mod goto_definition;
 mod goto_type_definition;
 mod hover;
 mod inlay_hints;
+mod references;
 mod semantic_tokens;
 mod semantic_tokens_range;
 mod shutdown;
@@ -18,6 +19,7 @@ pub(super) use goto_definition::GotoDefinitionRequestHandler;
 pub(super) use goto_type_definition::GotoTypeDefinitionRequestHandler;
 pub(super) use hover::HoverRequestHandler;
 pub(super) use inlay_hints::InlayHintRequestHandler;
+pub(super) use references::ReferencesRequestHandler;
 pub(super) use semantic_tokens::SemanticTokensRequestHandler;
 pub(super) use semantic_tokens_range::SemanticTokensRangeRequestHandler;
 pub(super) use shutdown::ShutdownHandler;

crates/ty_server/src/server/api/requests/references.rs

@@ -0,0 +1,65 @@
+use std::borrow::Cow;
+
+use lsp_types::request::References;
+use lsp_types::{Location, ReferenceParams, Url};
+use ruff_db::source::{line_index, source_text};
+use ty_ide::references;
+use ty_project::ProjectDatabase;
+
+use crate::document::{PositionExt, ToLink};
+use crate::server::api::traits::{
+    BackgroundDocumentRequestHandler, RequestHandler, RetriableRequestHandler,
+};
+use crate::session::DocumentSnapshot;
+use crate::session::client::Client;
+
+pub(crate) struct ReferencesRequestHandler;
+
+impl RequestHandler for ReferencesRequestHandler {
+    type RequestType = References;
+}
+
+impl BackgroundDocumentRequestHandler for ReferencesRequestHandler {
+    fn document_url(params: &ReferenceParams) -> Cow<Url> {
+        Cow::Borrowed(&params.text_document_position.text_document.uri)
+    }
+
+    fn run_with_snapshot(
+        db: &ProjectDatabase,
+        snapshot: DocumentSnapshot,
+        _client: &Client,
+        params: ReferenceParams,
+    ) -> crate::server::Result<Option<Vec<Location>>> {
+        if snapshot.client_settings().is_language_services_disabled() {
+            return Ok(None);
+        }
+
+        let Some(file) = snapshot.file(db) else {
+            return Ok(None);
+        };
+
+        let source = source_text(db, file);
+        let line_index = line_index(db, file);
+        let offset = params.text_document_position.position.to_text_size(
+            &source,
+            &line_index,
+            snapshot.encoding(),
+        );
+
+        let include_declaration = params.context.include_declaration;
+
+        let Some(references_result) = references(db, file, offset, include_declaration) else {
+            return Ok(None);
+        };
+
+        let locations: Vec<_> = references_result
+            .into_iter()
+            .flat_map(|ranged| ranged.value.into_iter())
+            .filter_map(|target| target.to_location(db, snapshot.encoding()))
+            .collect();
+
+        Ok(Some(locations))
+    }
+}
+
+impl RetriableRequestHandler for ReferencesRequestHandler {}

crates/ty_server/src/snapshots/ty_server__server__tests__initialization.snap

@@ -26,6 +26,7 @@ expression: initialization_result
     },
     "definitionProvider": true,
     "typeDefinitionProvider": true,
+    "referencesProvider": true,
     "declarationProvider": true,
     "semanticTokensProvider": {
       "legend": {

crates/ty_server/src/snapshots/ty_server__server__tests__initialization_with_workspace.snap

@@ -26,6 +26,7 @@ expression: initialization_result
     },
     "definitionProvider": true,
     "typeDefinitionProvider": true,
+    "referencesProvider": true,
     "declarationProvider": true,
     "semanticTokensProvider": {
       "legend": {