A no-move tier waits for no new report, so its walk asks the next tier (issue 648)

A build made from the source every machine running it runs is marked sent
and sent nothing, yet the tier's wait asked each machine for a report after
that marking. None follows, and the walk waited for ever. Each machine is
now judged by whether it answered its last send, the one whose builds made
the build no move.

cmd/mesh-controller/release_plan.go

@@ -251,6 +251,16 @@ func gates(p inventory.Plan, edges []inventory.Edge, rollsOut func(string) bool)
 	return out
 }
 
+// noMoveWhy is what a plan says of a module of its tier whose build was made from the source every machine
+// running it runs (novox/hq issue 280): nothing is sent for it.
+const noMoveWhy = "no move: made from the source every machine running it runs"
+
+// noMove is whether the plan marked the module no move and sent it nothing. Read from what the plan says,
+// so a plan kept before the mark had a name of its own is read the same (novox/hq issue 648).
+func noMove(s *inventory.PlanModule) bool {
+	return s != nil && s.FirstAt == nil && s.Gate == nil && strings.HasPrefix(s.Why, "no move")
+}
+
 // applied says whether every machine running the module has reported since the module was built.
 // appliedEach is applied with a moment of its own for each machine: the reports that count are the ones
 // after that machine was sent the build (novox/hq issue 256).
@@ -805,7 +815,7 @@ func advanceOnce(ctx context.Context, open *stores, p *inventory.Plan,
 			} else if same {
 				now := time.Now().UTC()
 				state.SentAt = &now
-				state.Why = "no move: made from the source every machine running it runs"
+				state.Why = noMoveWhy
 				fmt.Printf("%s: %s built from the source every machine running it runs: no move, nothing sent\n", p.ID, m)
 				continue
 			}
@@ -995,6 +1005,25 @@ func advanceOnce(ctx context.Context, open *stores, p *inventory.Plan,
 			if state.BuiltAt != nil {
 				since = *state.BuiltAt
 			}
+			// **A build that is no move is waited on by the send that last carried it** (novox/hq issue 648).
+			// Nothing was sent for it, so no report follows its marking or its build: a machine that does not
+			// happen to report again held the walk for ever. Each machine runs it once it answered its last
+			// send — the one whose builds made it no move — whenever that was.
+			if noMove(state) {
+				byNode := map[string]inventory.Reported{}
+				for _, r := range reports {
+					byNode[r.Node] = r
+				}
+				if ok, on := appliedEach(m, func(node string) time.Time {
+					if s := byNode[node].Sent; s != nil {
+						return *s
+					}
+					return time.Time{}
+				}, running, reports); !ok {
+					waiting = append(waiting, fmt.Sprintf("%s on %s", m, strings.Join(on, ", ")))
+				}
+				continue
+			}
 			// **Each machine from its own send** (novox/hq issue 256). With one machine first (ADR 0218)
 			// a module is sent twice — the first machine, then the rest — and SentAt is the second.
 			// Asked of every machine, the first machine's report, made between the two sends, read as