Add folding ranges (#815)

Author: kv9898

crates/ark/src/lsp/backend.rs

@@ -24,6 +24,7 @@ use tower_lsp::jsonrpc;
 use tower_lsp::jsonrpc::Result;
 use tower_lsp::lsp_types::request::GotoImplementationParams;
 use tower_lsp::lsp_types::request::GotoImplementationResponse;
+use tower_lsp::lsp_types::FoldingRange;
 use tower_lsp::lsp_types::SelectionRange;
 use tower_lsp::lsp_types::*;
 use tower_lsp::Client;
@@ -131,6 +132,7 @@ pub(crate) enum LspRequest {
     Initialize(InitializeParams),
     WorkspaceSymbol(WorkspaceSymbolParams),
     DocumentSymbol(DocumentSymbolParams),
+    FoldingRange(FoldingRangeParams),
     ExecuteCommand(ExecuteCommandParams),
     Completion(CompletionParams),
     CompletionResolve(CompletionItem),
@@ -153,6 +155,7 @@ pub(crate) enum LspResponse {
     Initialize(InitializeResult),
     WorkspaceSymbol(Option<Vec<SymbolInformation>>),
     DocumentSymbol(Option<DocumentSymbolResponse>),
+    FoldingRange(Option<Vec<FoldingRange>>),
     ExecuteCommand(Option<Value>),
     Completion(Option<CompletionResponse>),
     CompletionResolve(CompletionItem),
@@ -263,6 +266,14 @@ impl LanguageServer for Backend {
         )
     }
 
+    async fn folding_range(&self, params: FoldingRangeParams) -> Result<Option<Vec<FoldingRange>>> {
+        cast_response!(
+            self,
+            self.request(LspRequest::FoldingRange(params)).await,
+            LspResponse::FoldingRange
+        )
+    }
+
     async fn execute_command(
         &self,
         params: ExecuteCommandParams,