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/state.go

@@ -423,6 +423,12 @@ func (c *Conn) StateWatch(module, name, pattern string, deliver func(StateChange
 	go func() {
 		initial := true
 		for e := range w.Updates() {
+			// A watch given up, or stopped, hands over nothing more, though values stay buffered in the
+			// watcher: they would reach a watch id the bundle no longer holds (issue 774: 1257 orphan
+			// changes after 51 failed watches).
+			if watching.Err() != nil {
+				break
+			}
 			if e == nil {
 				// The end of what was there when the watch began.
 				if initial {
@@ -431,6 +437,11 @@ func (c *Conn) StateWatch(module, name, pattern string, deliver func(StateChange
 				}
 				continue
 			}
+			if initial {
+				// Arrival from the bus is progress before the bundle is asked: the bound measures the current
+				// values coming in, and restarts when the bundle has taken one.
+				progress()
+			}
 			change := StateChange{State: name, Key: e.Key(), Revision: e.Revision(), Current: initial}
 			switch e.Operation() {
 			case jetstream.KeyValuePut:
@@ -451,6 +462,9 @@ func (c *Conn) StateWatch(module, name, pattern string, deliver func(StateChange
 					change.Op = "expire"
 				}
 			}
+			if watching.Err() != nil {
+				break
+			}
 			if err := deliver(change); err != nil {
 				c.Logf("[mesh-tools] %s did not take %s %s of %s: %v; its next change, or its next start, reads it again",
 					module, change.Op, change.Key, name, err)