[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

@@ -64,6 +64,9 @@ class LoadedExecutablePlugin {
   /// Callbacks to be called when the connection is restored.
   llvm::SmallVector<std::function<void(void)> *, 0> onReconnect;
 
+  /// Flag to dump plugin messagings.
+  bool dumpMessaging = false;
+
   /// Cleanup function to call ASTGen.
   std::function<void(void)> cleanup;
 
@@ -121,6 +124,8 @@ class LoadedExecutablePlugin {
 
   const void *getCapability() { return capability; };
   void setCapability(const void *newValue) { capability = newValue; };
+
+  void setDumpMessaging(bool flag) { dumpMessaging = flag; }
 };
 
 class PluginRegistry {
@@ -131,7 +136,12 @@ class PluginRegistry {
   llvm::StringMap<std::unique_ptr<LoadedExecutablePlugin>>
       LoadedPluginExecutables;
 
+  /// Flag to dump plugin messagings.
+  bool dumpMessaging = false;
+
 public:
+  PluginRegistry();
+
   /// Load a dynamic link library specified by \p path.
   /// If \p path plugin is already loaded, this returns the cached object.
   llvm::Expected<void *> loadLibraryPlugin(llvm::StringRef path);

lib/AST/PluginRegistry.cpp

@@ -40,6 +40,10 @@
 
 using namespace swift;
 
+PluginRegistry::PluginRegistry() {
+  dumpMessaging = ::getenv("SWIFT_DUMP_PLUGIN_MESSAGING") != nullptr;
+}
+
 llvm::Expected<void *> PluginRegistry::loadLibraryPlugin(StringRef path) {
   auto found = LoadedPluginLibraries.find(path);
   if (found != LoadedPluginLibraries.end()) {
@@ -94,6 +98,8 @@ PluginRegistry::loadExecutablePlugin(StringRef path) {
   auto plugin = std::unique_ptr<LoadedExecutablePlugin>(
       new LoadedExecutablePlugin(path, stat.getLastModificationTime()));
 
+  plugin->setDumpMessaging(dumpMessaging);
+
   // Launch here to see if it's actually executable, and diagnose (by returning
   // an error) if necessary.
   if (auto error = plugin->spawnIfNeeded()) {
@@ -213,6 +219,10 @@ ssize_t LoadedExecutablePlugin::PluginProcess::write(const void *buf,
 llvm::Error LoadedExecutablePlugin::sendMessage(llvm::StringRef message) const {
   ssize_t writtenSize = 0;
 
+  if (dumpMessaging) {
+    llvm::dbgs() << "->(plugin:" << Process->pid << ") " << message << "\n";
+  }
+
   const char *data = message.data();
   size_t size = message.size();
 
@@ -269,5 +279,9 @@ llvm::Expected<std::string> LoadedExecutablePlugin::waitForNextMessage() const {
     message.append(buffer, readSize);
   }
 
+  if (dumpMessaging) {
+    llvm::dbgs() << "<-(plugin:" << Process->pid << ") " << message << "\n";
+  }
+
   return message;
 }

lib/ASTGen/Sources/ASTGen/PluginHost.swift

@@ -103,10 +103,6 @@ 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 {
@@ -122,10 +118,6 @@ 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)
   }