Add prepare rename provider

Author: amiralies

server/src/server.ts

@@ -282,6 +282,48 @@ function references(msg: p.RequestMessage) {
   return response;
 }
 
+function prepareRename(msg: p.RequestMessage) {
+  // https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_prepareRename
+  let params = msg.params as p.PrepareRenameParams;
+  let filePath = fileURLToPath(params.textDocument.uri);
+  let locations: null | p.Location[] = utils.getReferencesForPosition(
+    filePath,
+    params.position
+  );
+
+  let result: p.Range | null = null;
+
+  if (locations !== null && locations.length > 0) {
+    let targetLoc = locations.find(loc => {
+      if (
+        path.normalize(fileURLToPath(loc.uri)) ===
+        path.normalize(fileURLToPath(params.textDocument.uri))
+      ) {
+        let { start, end } = loc.range;
+        let pos = params.position;
+
+        return (
+          start.character <= pos.character &&
+          start.line <= pos.line &&
+          end.character >= pos.character &&
+          end.line >= pos.line
+        );
+      }
+    });
+
+    if (targetLoc != null) {
+      result = targetLoc.range;
+    }
+  }
+
+  let response: m.ResponseMessage = {
+    jsonrpc: c.jsonrpcVersion,
+    id: msg.id,
+    result
+  };
+  return response;
+}
+
 function rename(msg: p.RequestMessage) {
   // https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_rename
   let params = msg.params as p.RenameParams;
@@ -591,7 +633,7 @@ function onMessage(msg: m.Message) {
           hoverProvider: true,
           definitionProvider: true,
           referencesProvider: true,
-          renameProvider: true,
+          renameProvider: { prepareProvider: true },
           documentSymbolProvider: false,
           completionProvider: { triggerCharacters: [".", ">", "@", "~"] },
         },
@@ -642,6 +684,8 @@ function onMessage(msg: m.Message) {
       send(definition(msg));
     } else if (msg.method === p.ReferencesRequest.method) {
       send(references(msg));
+    } else if (msg.method === p.PrepareRenameRequest.method) {
+      send(prepareRename(msg));
     } else if (msg.method === p.RenameRequest.method) {
       send(rename(msg));
     } else if (msg.method === p.DocumentSymbolRequest.method) {