[clangd] Don't crash on empty textDocument/didChange.

Found by clangd-fuzzer.

llvm-svn: 316652

clang-tools-extra/clangd/ClangdLSPServer.cpp

@@ -73,6 +73,8 @@ void ClangdLSPServer::onDocumentDidOpen(Ctx C,
 
 void ClangdLSPServer::onDocumentDidChange(Ctx C,
                                           DidChangeTextDocumentParams &Params) {
+  if (Params.contentChanges.size() != 1)
+    return C.replyError(-32602, "can only apply one change at a time");
   // We only support full syncing right now.
   Server.addDocument(Params.textDocument.uri.file,
                      Params.contentChanges[0].text);

clang-tools-extra/test/clangd/protocol.test

@@ -26,6 +26,10 @@ Content-Length: 246
 
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":"struct fake { int a, bb, ccc; int f(int i, const float f) const; };\nint main() {\n  fake f;\n  f.\n}\n"}}}
 
+Content-Length: 104
+
+{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///main.cpp"}}}
+
 Content-Type: application/vscode-jsonrpc; charset-utf-8
 Content-Length: 146