[clangd] Refactor JSON-over-stdin/stdout code into Transport abstraction. (re-land r344620)

Summary:
This paves the way for alternative transports (mac XPC, maybe messagepack?),
and also generally improves layering: testing ClangdLSPServer becomes less of
a pipe dream, we split up the JSONOutput monolith, etc.

This isn't a final state, much of what remains in JSONRPCDispatcher can go away,
handlers can call reply() on the transport directly, JSONOutput can be renamed
to StreamLogger and removed, etc. But this patch is sprawling already.

The main observable change (see tests) is that hitting EOF on input is now an
error: the client should send the 'exit' notification.
This is defensible: the protocol doesn't spell this case out. Reproducing the
current behavior for all combinations of shutdown/exit/EOF clutters interfaces.
We can iterate on this if desired.

Reviewers: jkorous, ioeric, hokein

Subscribers: mgorny, ilya-biryukov, MaskRay, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D53286

llvm-svn: 344672

1 files changed, 17 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
index 7026d47b981..940c78f1d59 100644
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -48,6 +48,23 @@ enum class ErrorCode {
   // Defined by the protocol.
   RequestCancelled = -32800,
 };
+// Models an LSP error as an llvm::Error.
+class LSPError : public llvm::ErrorInfo<LSPError> {
+public:
+  std::string Message;
+  ErrorCode Code;
+  static char ID;
+
+  LSPError(std::string Message, ErrorCode Code)
+      : Message(std::move(Message)), Code(Code) {}
+
+  void log(llvm::raw_ostream &OS) const override {
+    OS << int(Code) << ": " << Message;
+  }
+  std::error_code convertToErrorCode() const override {
+    return llvm::inconvertibleErrorCode();
+  }
+};
 
 struct URIForFile {
   URIForFile() = default;