[Macro] Add env variable option to dump exectuable plugin messagings

Set 'SWIFT_DUMP_PLUGIN_MESSAGING' env variable to enable it.

Author: rintaro

include/swift/AST/PluginRegistry.h

@@ -32,6 +32,9 @@ class LoadedExecutablePlugin {
   /// value from ASTGen.
   const void *capability = nullptr;
 
+  /// Flag to dump plugin messagings.
+  bool dumpMessaging = false;
+
   /// Cleanup function to call ASTGen.
   std::function<void(void)> cleanup;
 
@@ -67,6 +70,8 @@ class LoadedExecutablePlugin {
 
   const void *getCapability() { return capability; };
   void setCapability(const void *newValue) { capability = newValue; };
+
+  void setDumpMessaging(bool flag) { dumpMessaging = flag; }
 };
 
 class PluginRegistry {

lib/AST/PluginRegistry.cpp

@@ -111,6 +111,9 @@ PluginRegistry::loadExecutablePlugin(StringRef path) {
       childInfo->Pid, stat.getLastModificationTime(),
       childInfo->ReadFileDescriptor, childInfo->WriteFileDescriptor));
 
+  const char *dumpMessaging = ::getenv("SWIFT_DUMP_PLUGIN_MESSAGING");
+  plugin->setDumpMessaging(dumpMessaging != nullptr);
+
   return plugin.get();
 }
 
@@ -181,6 +184,10 @@ ssize_t LoadedExecutablePlugin::write(const void *buf, size_t nbyte) const {
 llvm::Error LoadedExecutablePlugin::sendMessage(llvm::StringRef message) const {
   ssize_t writtenSize = 0;
 
+  if (dumpMessaging) {
+    llvm::dbgs() << "->(plugin:" << pid << ") " << message << "\n";
+  }
+
   const char *data = message.data();
   size_t size = message.size();
 
@@ -233,5 +240,9 @@ llvm::Expected<std::string> LoadedExecutablePlugin::waitForNextMessage() const {
     message.append(buffer, readSize);
   }
 
+  if (dumpMessaging) {
+    llvm::dbgs() << "<-(plugin:" << pid << ") " << message << "\n";
+  }
+
   return message;
 }

lib/ASTGen/Sources/ASTGen/PluginHost.swift

@@ -48,10 +48,6 @@ struct CompilerPlugin {
 
   private func sendMessage(_ message: HostToPluginMessage) throws {
     let hadError = try LLVMJSON.encoding(message) { (data) -> Bool in
-//      // FIXME: Add -dump-plugin-message option?
-//      data.withMemoryRebound(to: UInt8.self) { buffer in
-//        print(">> " + String(decoding: buffer, as: UTF8.self))
-//      }
       return Plugin_sendMessage(opaqueHandle, BridgedData(baseAddress: data.baseAddress, size: data.count))
     }
     if hadError {
@@ -67,10 +63,6 @@ struct CompilerPlugin {
       throw PluginError.failedToReceiveMessage
     }
     let data = UnsafeBufferPointer(start: result.baseAddress, count: result.size)
-//    // FIXME: Add -dump-plugin-message option?
-//    data.withMemoryRebound(to: UInt8.self) { buffer in
-//      print("<< " + String(decoding: buffer, as: UTF8.self))
-//    }
     return try LLVMJSON.decode(PluginToHostMessage.self, from: data)
   }