fix: allow Child() to accept relative 'kind/id' path (backwards compatible)

actor/context.go

@@ -136,10 +136,18 @@ func (c *Context) Parent() *PID {
 	return nil
 }
 
-// Child will return the PID of the child (if any) by the given name/id.
-// PID will be nil if it could not find it.
+// Child will return the PID of the child (if any) by the given id.
+// The id can be a relative path (e.g., "child/1") or a full path (e.g., "parent/1/child/1").
+// Returns nil if the child could not be found.
 func (c *Context) Child(id string) *PID {
-	pid, _ := c.children.Get(id)
+	// First try exact match (backward compatibility)
+	if pid, ok := c.children.Get(id); ok {
+		return pid
+	}
+
+	// Then try with parent prefix
+	fullKey := c.pid.ID + pidSeparator + id
+	pid, _ := c.children.Get(fullKey)
 	return pid
 }
 

actor/context_test.go

@@ -66,6 +66,11 @@ func TestSpawnChildPID(t *testing.T) {
 		case Started:
 			pid := c.SpawnChildFunc(childfn, "child", WithID("1"))
 			assert.True(t, expectedPID.Equals(pid))
+
+			pid = c.Child("child/1")
+			assert.NotNil(t, pid)
+			assert.True(t, expectedPID.Equals(pid))
+
 			wg.Done()
 		case Stopped:
 		}

cluster/cluster_test.go

@@ -410,6 +410,41 @@ func TestCannotDuplicateActor(t *testing.T) {
 	c2.Stop()
 }
 
+func TestClusterChildLookup(t *testing.T) {
+	var (
+		c1Addr = getRandomLocalhostAddr()
+		c1     = makeCluster(t, c1Addr, "A", "eu-west")
+		wg     = sync.WaitGroup{}
+	)
+
+	wg.Add(1)
+	c1.engine.SpawnFunc(func(c *actor.Context) {
+		switch c.Message().(type) {
+		case actor.Started:
+			childPID := c.SpawnChildFunc(func(_ *actor.Context) {}, "worker", actor.WithID("1"))
+
+			// Test relative path lookup (new behavior)
+			found := c.Child("worker/1")
+			assert.NotNil(t, found)
+			assert.True(t, childPID.Equals(found))
+
+			// Test full path lookup (backward compatible)
+			fullPath := c.PID().ID + "/worker/1"
+			foundFull := c.Child(fullPath)
+			assert.NotNil(t, foundFull)
+			assert.True(t, childPID.Equals(foundFull))
+
+			assert.Equal(t, c1Addr, childPID.Address)
+
+			wg.Done()
+		}
+	}, "parent", actor.WithID("1"))
+
+	c1.Start()
+	wg.Wait()
+	c1.Stop()
+}
+
 func makeCluster(t *testing.T, addr, id, region string) *Cluster {
 	config := NewConfig().
 		WithID(id).