Move null preprocessing of relative path back to the constructor of WatchEvent (because having it outside didn't lead to significantly simpler code overall)

Author: sungshik

src/main/java/engineering/swat/watch/WatchEvent.java

@@ -28,6 +28,8 @@
 
 import java.nio.file.Path;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 /**
  * The library publishes these events to all subscribers, they are immutable and safe to share around.
  */
@@ -67,13 +69,13 @@ public enum Kind {
     private final Path relativePath;
 
     public WatchEvent(Kind kind, Path rootPath) {
-        this(kind, rootPath, Path.of(""));
+        this(kind, rootPath, null);
     }
 
-    public WatchEvent(Kind kind, Path rootPath, Path relativePath) {
+    public WatchEvent(Kind kind, Path rootPath, @Nullable Path relativePath) {
         this.kind = kind;
         this.rootPath = rootPath;
-        this.relativePath = relativePath;
+        this.relativePath = relativePath == null ? Path.of("") : relativePath;
     }
 
     public Kind getKind() {

src/main/java/engineering/swat/watch/impl/jdk/JDKBaseWatch.java

@@ -90,12 +90,9 @@ protected boolean startIfFirstTime() throws IOException {
     }
 
     protected WatchEvent translate(java.nio.file.WatchEvent<?> jdkEvent) {
-        var jdkKind = jdkEvent.kind();
-        var context = jdkKind == StandardWatchEventKinds.OVERFLOW ? null : jdkEvent.context();
-
-        var kind = translate(jdkKind);
+        var kind = translate(jdkEvent.kind());
         var rootPath = path;
-        var relativePath = context == null ? Path.of("") : (Path) context;
+        var relativePath = kind == WatchEvent.Kind.OVERFLOW ? null : (@Nullable Path) jdkEvent.context();
 
         var event = new WatchEvent(kind, rootPath, relativePath);
         logger.trace("Translated: {} to {}", jdkEvent, event);