node-tools: say whose words a refused event is (hq issue 276)

"plex did not take radarr.download.completed: Unexpected end of JSON input"
read as the runtime failing to parse the bundle's answer. It was plex's own
handler error, relayed. A bundle's error answer is now a launch.Refused, and
the line says the handler answered an error, quotes it, names the event id
and the delay before the next offer; the runtime's own failures (no answer
in time, bundle exited) are said as before.

The rule, unchanged and now tested: any mesh/event answer that is not an
error takes the event, whatever its result says, including none.

node-tools/internal/runtime/runtime.go

@@ -7,6 +7,7 @@ package runtime
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -565,7 +566,8 @@ func (b *moduleBus) Subscribe(deliver func(json.RawMessage) error) error {
 		c.mu.Unlock()
 		for _, d := range targets {
 			if err := (*d)(raw); err != nil {
-				c.logf("[mesh-tools] %s did not take %s: %v; offered again", module, env.Key, err)
+				c.logf("[mesh-tools] %s did not take %s%s: %s; offered again in %s", module, env.Key,
+					eventRef(env), whyNotTaken(err), bus.NakDelay)
 				return err
 			}
 		}
@@ -579,6 +581,26 @@ func (b *moduleBus) Subscribe(deliver func(json.RawMessage) error) error {
 	return nil
 }
 
+// whyNotTaken says why a bundle did not take an event, so the line names who failed: the module's
+// handler, in its own words — an error it answered — or the runtime not reaching it. A bundle's
+// handler error read bare ("Unexpected end of JSON input") looked like the runtime's (issue 276).
+func whyNotTaken(err error) string {
+	var refused *launch.Refused
+	if errors.As(err, &refused) {
+		return fmt.Sprintf("its handler answered an error, in its own words: %q (an event is taken by any answer that is not an error)", refused.Message)
+	}
+	return err.Error()
+}
+
+// eventRef names the event a line is about by its id, when it has one, so its offers can be told
+// apart from another event's.
+func eventRef(env bus.Envelope) string {
+	if id := env.Headers["x-event-id"]; id != "" {
+		return " (event " + id + ")"
+	}
+	return ""
+}
+
 // stateAsked is what a bundle names when it reaches its state (ADR 0201): the state by the name its
 // module uses, a key, and for a put the value.
 type stateAsked struct {