A watch given up or stopped hands over nothing more; arrival of current values restarts its bound (issue 774)

Quick: check the watch context before each deliver in StateWatch. Thorough (chosen, same
file kind): also LogWatch drops a message fetched as it stopped, and the bound restarts
on arrival, not only after the bundle took a value.

node-tools/internal/bus/log.go

@@ -9,6 +9,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/nats-io/nats.go"
@@ -381,18 +382,19 @@ func (c *Conn) LogWatch(module, name, keys string, from uint64, since time.Time,
 			return nil, fmt.Errorf("the watch of %s: %w", name, err)
 		}
 	}
+	var stopped atomic.Bool
 	go func() {
 		for {
 			m, err := it.Next()
-			if err != nil {
-				return // stopped, or the connection closed
+			if err != nil || stopped.Load() {
+				return // stopped, or the connection closed; a message fetched as it stopped is not handed over
 			}
 			if err := hand(m); err != nil {
 				c.Logf("[mesh-tools] %s did not take entry of %s: %v; it is in the log, a read finds it", module, name, err)
 			}
 		}
 	}()
-	return it.Stop, nil
+	return func() { stopped.Store(true); it.Stop() }, nil
 }
 
 // LogLast is a key's last entry, or nil when it has none.