Turns out we don't need the encoding after all since all methods are overridden

src/core/lombok/javac/apt/LombokFileObjects.java

@@ -26,7 +26,6 @@ import java.io.IOException;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.net.URI;
-import java.nio.charset.Charset;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Iterator;
@@ -37,7 +36,6 @@ import javax.tools.FileObject;
 import javax.tools.JavaFileManager;
 import javax.tools.JavaFileObject;
 import javax.tools.JavaFileObject.Kind;
-import javax.tools.StandardLocation;
 
 import lombok.core.DiagnosticsReceiver;
 
@@ -127,8 +125,7 @@ final class LombokFileObjects {
 				if (superType.isInstance(wrappedManager)) {
 					return new Java9Compiler(wrappedManager);
 				} else {
-					String encoding = getEncodingOf(wrappedManager);
-					return new Java9Compiler(new BaseFileManagerWrapper(wrappedManager, encoding != null ? Charset.forName(encoding) : null));
+					return new Java9Compiler(new BaseFileManagerWrapper(wrappedManager));
 				}
 			}
 			catch (Exception e) {}
@@ -151,24 +148,12 @@ final class LombokFileObjects {
 		}
 		throw new IllegalArgumentException(sb.toString());
 	}
-
-	private static String getEncodingOf(JavaFileManager manager) {
-		try {
-			// FileObject may be instance of org.jetbrains.jps.javac.OutputFileObject
-            FileObject fo = manager.getFileForOutput(StandardLocation.CLASS_OUTPUT, "", "dummy", null);
-            Field encodingField = fo.getClass().getDeclaredField("myEncodingName");
-            encodingField.setAccessible(true);
-            return (String)encodingField.get(fo);
-        } catch (Exception e) {
-            return null;
-        }
-	}
-
+	
 	static class BaseFileManagerWrapper extends BaseFileManager {
 		JavaFileManager manager;
-
-		public BaseFileManagerWrapper(JavaFileManager manager, Charset charset) {
-			super(charset);
+		
+		public BaseFileManagerWrapper(JavaFileManager manager) {
+			super(null);
 			this.manager = manager;
 		}
 		
@@ -176,62 +161,62 @@ final class LombokFileObjects {
 		public int isSupportedOption(String option) {
 			return manager.isSupportedOption(option);
 		}
-
+		
 		@Override
 		public ClassLoader getClassLoader(Location location) {
 			return manager.getClassLoader(location);
 		}
-
+		
 		@Override
 		public Iterable<JavaFileObject> list(Location location, String packageName, Set<Kind> kinds, boolean recurse) throws IOException {
 			return manager.list(location, packageName, kinds, recurse);
 		}
-
+		
 		@Override
 		public String inferBinaryName(Location location, JavaFileObject file) {
 			return manager.inferBinaryName(location, file);
 		}
-
+		
 		@Override
 		public boolean isSameFile(FileObject a, FileObject b) {
 			return manager.isSameFile(a, b);
 		}
-
+		
 		@Override
 		public boolean handleOption(String current, Iterator<String> remaining) {
 			return manager.handleOption(current, remaining);
 		}
-
+		
 		@Override
 		public boolean hasLocation(Location location) {
 			return manager.hasLocation(location);
 		}
-
+		
 		@Override
 		public JavaFileObject getJavaFileForInput(Location location, String className, Kind kind) throws IOException {
 			return manager.getJavaFileForInput(location, className, kind);
 		}
-
+		
 		@Override
 		public JavaFileObject getJavaFileForOutput(Location location, String className, Kind kind, FileObject sibling) throws IOException {
 			return manager.getJavaFileForOutput(location, className, kind, sibling);
 		}
-
+		
 		@Override
 		public FileObject getFileForInput(Location location, String packageName, String relativeName) throws IOException {
 			return manager.getFileForInput(location, packageName, relativeName);
 		}
-
+		
 		@Override
 		public FileObject getFileForOutput(Location location, String packageName, String relativeName, FileObject sibling) throws IOException {
 			return manager.getFileForOutput(location, packageName, relativeName, sibling);
 		}
-
+		
 		@Override
 		public void flush() throws IOException {
 			manager.flush();
 		}
-
+		
 		@Override
 		public void close() throws IOException {
 			manager.close();