fix(commons): synchronize in ScopedValue.Carrier since child threads may access values from parent threads

commons/src/main/java/io/gitlab/jfronny/commons/concurrent/ScopedValue.java

@@ -3,6 +3,7 @@ package io.gitlab.jfronny.commons.concurrent;
 import java.util.Deque;
 import java.util.LinkedList;
 import java.util.NoSuchElementException;
+import java.util.Optional;
 import java.util.concurrent.Callable;
 import java.util.function.Supplier;
 
@@ -75,8 +76,8 @@ public class ScopedValue<T> {
     }
 
     private static class Carrier<T> {
-        private Deque<T> value;
-        private Carrier<T> parent;
+        private final Deque<T> value;
+        private final Carrier<T> parent;
 
         public Carrier() {
             this(null);
@@ -87,10 +88,18 @@ public class ScopedValue<T> {
             this.parent = parent;
         }
 
+        private Optional<T> valueIfPresent() {
+            synchronized (value) {
+                if (!value.isEmpty()) return Optional.of(value.peek());
+                return Optional.empty();
+            }
+        }
+
         public T getValue() {
-            if (!value.isEmpty()) return value.peek();
-            if (parent == null) throw new NoSuchElementException("No value present");
-            return parent.getValue();
+            return valueIfPresent().orElseGet(() -> {
+                if (parent == null) throw new NoSuchElementException("No value present");
+                return parent.getValue();
+            });
         }
 
         public boolean isPresent() {
@@ -100,21 +109,27 @@ public class ScopedValue<T> {
         }
 
         public void setValue(T value) {
-            this.value.push(value);
+            synchronized (this.value) {
+                this.value.push(value);
+            }
         }
 
         public void clear() {
-            value.pop();
+            synchronized (this.value) {
+                value.pop();
+            }
         }
 
         public T orElse(T other) {
-            if (!value.isEmpty()) return value.peek();
-            if (parent == null) return other;
-            return parent.orElse(other);
+            return valueIfPresent().orElseGet(() -> {
+                if (parent == null) return other;
+                return parent.orElse(other);
+            });
         }
 
         public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {
-            if (!value.isEmpty()) return value.peek();
+            Optional<T> v = valueIfPresent();
+            if (v.isPresent()) return v.get();
             if (parent == null) throw exceptionSupplier.get();
             return parent.orElseThrow(exceptionSupplier);
         }