================
@@ -100,22 +175,301 @@ template <typename Req, typename Resp, typename Evt>
class Transport {
virtual llvm::Expected<MainLoop::ReadHandleUP>
RegisterMessageHandler(MainLoop &loop, MessageHandler &handler) = 0;
- // FIXME: Refactor mcp::Server to not directly access log on the transport.
- // protected:
+protected:
template <typename... Ts> inline auto Logv(const char *Fmt, Ts &&...Vals) {
Log(llvm::formatv(Fmt, std::forward<Ts>(Vals)...).str());
}
virtual void Log(llvm::StringRef message) = 0;
+
+ /// Function object to reply to a call.
+ /// Each instance must be called exactly once, otherwise:
+ /// - the bug is logged, and (in debug mode) an assert will fire
+ /// - if there was no reply, an error reply is sent
+ /// - if there were multiple replies, only the first is sent
+ class ReplyOnce {
+ std::atomic<bool> replied = {false};
+ const Req req;
+ JSONTransport *transport; // Null when moved-from.
+ JSONTransport::MessageHandler *handler; // Null when moved-from.
+
+ public:
+ ReplyOnce(const Req req, JSONTransport *transport,
+ JSONTransport::MessageHandler *handler)
+ : req(req), transport(transport), handler(handler) {
+ assert(handler);
+ }
+ ReplyOnce(ReplyOnce &&other)
+ : replied(other.replied.load()), req(other.req),
+ transport(other.transport), handler(other.handler) {
+ other.transport = nullptr;
+ other.handler = nullptr;
+ }
+ ReplyOnce &operator=(ReplyOnce &&) = delete;
+ ReplyOnce(const ReplyOnce &) = delete;
+ ReplyOnce &operator=(const ReplyOnce &) = delete;
+
+ ~ReplyOnce() {
+ if (transport && handler && !replied) {
+ assert(false && "must reply to all calls!");
+ (*this)(MakeResponse<Req, Resp>(
+ req, llvm::createStringError("failed to reply")));
+ }
+ }
+
+ void operator()(const Resp &resp) {
+ assert(transport && handler && "moved-from!");
+ if (replied.exchange(true)) {
+ assert(false && "must reply to each call only once!");
+ return;
+ }
+
+ if (llvm::Error error = transport->Send(resp))
+ handler->OnError(std::move(error));
+ }
+ };
+
+public:
+ class Binder;
+ using BinderUP = std::unique_ptr<Binder>;
+
+ /// Binder collects a table of functions that handle calls.
----------------
JDevlieghere wrote:
I think this new class warrants a bit more documentation. IIUC, this is
basically a forwarded of messages, which allows you to register a handler by
name. By defining message types we can get that automatically out of the
messages, and then have it call the right callback?
Basically, this hoist the logic we have both in MCP and DAP into the transport
class. Which leads to my next question: does this need to be tied to
JSONTransport? Can this be built on top of an arbitrary transport?
https://github.com/llvm/llvm-project/pull/159160
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