Document positional encoding fallback in LSP server initialization

Reviewed By: captbaritone

Differential Revision: D63918136

fbshipit-source-id: d8daf5cbcabe861d0b4ba37bb0c58e939d4c7335

compiler/crates/relay-lsp/src/server.rs

@@ -105,6 +105,12 @@ pub use crate::LSPExtraDataProvider;
 /// Initializes an LSP connection, handling the `initialize` message and `initialized` notification
 /// handshake.
 pub fn initialize(connection: &Connection) -> LSPProcessResult<InitializeParams> {
+    // We don't currently negotiate character encoding in the Relay LSP.
+    // This means we fall back to the LSP default of UTF-16, but we make no effort to
+    // ensure that the LSP positions we emit are actually representing the source text as UTF-16.
+    // This is a possible source of positioning issues, but in lieu of having a reproducible bug,
+    // we're leaving it how it is for now.
+
     let server_capabilities = ServerCapabilities {
         // Enable text document syncing so we can know when files are opened/changed/saved/closed
         text_document_sync: Some(TextDocumentSyncCapability::Kind(TextDocumentSyncKind::FULL)),