[clangd] Support utf-8 offsets (rather than utf-16) as a protocol extension

Summary:
Still some pieces to go here: unit tests for new SourceCode functionality and
a command-line flag to force utf-8 mode. But wanted to get early feedback.

Reviewers: hokein

Subscribers: ilya-biryukov, ioeric, MaskRay, jkorous, arphaman, kadircet, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58275

llvm-svn: 357102

1 files changed, 15 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
index 468ead8df17..7cf414123f1 100644
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -338,6 +338,18 @@ SymbolKind adjustKindToCapability(SymbolKind Kind,
 // https://github.com/Microsoft/language-server-protocol/issues/344
 SymbolKind indexSymbolKindToSymbolKind(index::SymbolKind Kind);
 
+// Determines the encoding used to measure offsets and lengths of source in LSP.
+enum class OffsetEncoding {
+  // Any string is legal on the wire. Unrecognized encodings parse as this.
+  UnsupportedEncoding,
+  // Length counts code units of UTF-16 encoded text. (Standard LSP behavior).
+  UTF16,
+  // Length counts bytes of UTF-8 encoded text. (Clangd extension).
+  UTF8,
+};
+llvm::json::Value toJSON(const OffsetEncoding &);
+bool fromJSON(const llvm::json::Value &, OffsetEncoding &);
+
 // This struct doesn't mirror LSP!
 // The protocol defines deeply nested structures for client capabilities.
 // Instead of mapping them all, this just parses out the bits we care about.
@@ -369,6 +381,9 @@ struct ClientCapabilities {
   /// Client supports CodeAction return value for textDocument/codeAction.
   /// textDocument.codeAction.codeActionLiteralSupport.
   bool CodeActionStructure = false;
+
+  /// Supported encodings for LSP character offsets. (clangd extension).
+  llvm::Optional<std::vector<OffsetEncoding>> offsetEncoding;
 };
 bool fromJSON(const llvm::json::Value &, ClientCapabilities &);