[Lldb-commits] [lldb] [lldb] Refactoring JSONTransport into an abstract RPC Message Handler and transport layer. (PR #153121)

[Pavel Labath via lldb-commits]

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@@ -54,112 +50,226 @@ class TransportUnhandledContentsError
   std::string m_unhandled_contents;
 };
 
-class TransportInvalidError : public llvm::ErrorInfo<TransportInvalidError> {
+/// A transport is responsible for maintaining the connection to a client
+/// application, and reading/writing structured messages to it.
+///
+/// Transports have limited thread safety requirements:
+///  - Messages will not be sent concurrently.
+///  - Messages MAY be sent while Run() is reading, or its callback is active.
+template <typename Req, typename Resp, typename Evt> class Transport {
 public:
-  static char ID;
-
-  TransportInvalidError() = default;
+  using Message = std::variant<Req, Resp, Evt>;
+
+  virtual ~Transport() = default;
+
+  /// Sends an event, a message that does not require a response.
+  virtual llvm::Error Event(const Evt &) = 0;
+  /// Sends a request, a message that expects a response.
+  virtual llvm::Error Request(const Req &) = 0;
+  /// Sends a response to a specific request.
+  virtual llvm::Error Response(const Resp &) = 0;
+
+  /// Implemented to handle incoming messages. (See Run() below).
+  class MessageHandler {
+  public:
+    virtual ~MessageHandler() = default;
+    /// Called when an event is received.
+    virtual void OnEvent(const Evt &) = 0;
+    /// Called when a request is received.
+    virtual void OnRequest(const Req &) = 0;
+    /// Called when a response is received.
+    virtual void OnResponse(const Resp &) = 0;
+
+    /// Called when an error occurs while reading from the transport.
+    ///
+    /// NOTE: This does *NOT* indicate that a specific request failed, but that
+    /// there was an error in the underlying transport.
+    virtual void OnError(MainLoopBase &, llvm::Error) = 0;
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labath wrote:

It's kinda weird that this is the only method that takes a mainloop argument. FWICS, this is only needed for the test as the real implementation holds a MainLoop variable anyway. Could the test version do the same?

https://github.com/llvm/llvm-project/pull/153121