A candidate answer shows every differing resource, masked; a module folded in the node's own is judged there; the node's own carries its bus membership as it runs it (issue 1126, seed #531)

novox's answer to seed #531 named 15 resources by id alone, so why each differed
was guessed. ModuleDiffers.Bodies keeps every differing resource with both
bodies, each value under a key a secret could be in masked (the same, another
seal of the same value, another value). The five old-form modules read
'removed' because the agent also lists them by module from the declaration kept
before the switch; they are judged inside the node's own. And the node's own
lacked bus-membership, which only the controller composes from its store: the
membership the node runs is carried, until the grants part hands it sealed.

go/compose/frombus/answer.go

@@ -107,7 +107,18 @@ func Answer(ctx context.Context, r Reader, mesh Mesh, s Scope, fps map[string]st
 		a.Verdict = delivery.VerdictOf(a)
 		return a
 	}
-	cmp := delivery.CompareComposed(composed, running)
+	// A module the composition folds inside the node's own is judged there: the agent also says it runs by module, from
+	// the declaration it kept before the switch (agent.Everything), which is no removal (issue 1126, seed #531).
+	if len(s.InOwn) > 0 {
+		var judged []delivery.Composed
+		for _, c := range running {
+			if c.Module == "" || !slices.Contains(s.InOwn, c.Module) {
+				judged = append(judged, c)
+			}
+		}
+		running = judged
+	}
+	cmp := delivery.CompareComposedWith(composed, running, s.SameValue)
 	// A refused module was composed as a stub: what it composed is no difference; its refusal is said.
 	notFailed := func(m string) bool { _, ok := failed[m]; return !ok }
 	a.Same = slices.DeleteFunc(cmp.Same, func(m string) bool { return !notFailed(m) })

go/compose/frombus/answer_rows_test.go

@@ -135,6 +135,25 @@ func answerNamesEveryRefusalAndLeavesAnOldBuildToTheNode(t *testing.T) {
 	if a.Verdict != delivery.CandidateSame {
 		t.Errorf("the fold's answer: %+v, want the same", a)
 	}
+	// (A) The agent also says spiegel runs by module, from the declaration kept before the switch (agent.Everything): a
+	// module the composition folds is judged inside the node's own, not as removed (issue 1126, seed #531's answer).
+	keptToo := append(append([]delivery.Composed{}, running...), delivery.Composed{Node: "n1", Module: "spiegel", Resources: carriedRes})
+	if a = Answer(ctx, b, Mesh{}, Scope{Node: "n1", Placements: given(b), InOwn: []string{"spiegel"}}, fps, keptToo, "h1", 3); a.Verdict != delivery.CandidateSame || len(a.Removed) != 0 {
+		t.Errorf("a folded module running from the kept declaration is answered %+v, want the same", a)
+	}
+	// (B) The node's own composition carries its bus membership as it runs it (the controller's, from its store): composed
+	// the same, not 'in what runs, not composed' (seed #531, novox).
+	membership := json.RawMessage(`{"id":"bus-membership","type":"file","path":"` + catalogue.BusMembershipPath + `","sealed":"{\"box\":\"m\"}","mode":"0600"}`)
+	withMembership := make([]delivery.Composed, 0, len(running))
+	for _, c := range running {
+		if c.Module == "" {
+			c.Resources = append(append([]json.RawMessage{}, c.Resources...), membership)
+		}
+		withMembership = append(withMembership, c)
+	}
+	if a = Answer(ctx, b, Mesh{}, Scope{Node: "n1", Placements: given(b), InOwn: []string{"spiegel"}}, fps, withMembership, "h1", 3); a.Verdict != delivery.CandidateSame {
+		t.Errorf("the node's own with its bus membership is answered %+v, want the same", a)
+	}
 	// Without what runs, the fold composes spiegel from its manifest, as before, and the composition refuses it.
 	if _, _, err := Compose(ctx, b, Mesh{}, Scope{Node: "n1", InOwn: []string{"spiegel"}}, fps); err == nil ||
 		!strings.Contains(err.Error(), "spiegel has not been built for this mesh") {

go/compose/frombus/frombus.go

@@ -124,6 +124,10 @@ type Scope struct {
 	Placements map[string]*delivery.Placement
 	InOwn      []string
 	Running    []delivery.Composed
+	// SameValue, in an answer, says whether two sealed values open to the same value (the node opens them with its own
+	// key), so a differing resource shows a value sealed again as such (delivery.CompareComposedWith). Nil shows them
+	// as differing.
+	SameValue func(a, b string) (same, known bool)
 }
 
 // InOwn is, of the modules p places on its node, those whose resources the node's own composition it runs
@@ -296,6 +300,16 @@ func input(ctx context.Context, r Reader, mesh Mesh, s Scope, refuse func(module
 				if s.Running[i].Module == "" {
 					own := s.Running[i]
 					n.RunsOwn = &own
+					// Its bus membership as it runs it: the controller composes it from its store, which the node does
+					// not read; until the grants part hands memberships sealed to the node, the node's own composition
+					// carries the one it runs (issue 1126, seed #531 on novox: "bus-membership in what runs, not
+					// composed", which applied would have taken the node's bus credential away).
+					if sealed := membershipOf(own); sealed != "" {
+						if in.BusMemberships == nil {
+							in.BusMemberships = map[string]string{}
+						}
+						in.BusMemberships[s.Node] = sealed
+					}
 				}
 			}
 		}
@@ -693,3 +707,18 @@ func storeSought(in compose.Input) string {
 	return said + "; " + catalogue.ArtifactStoreProvision + " is served by " + strings.Join(where, ", ") +
 		", none of it on the private network with a port"
 }
+
+// membershipOf is the sealed value of the bus membership resource (catalogue.BusMembershipID) of a node's own
+// composition, or "".
+func membershipOf(own delivery.Composed) string {
+	for _, raw := range own.Resources {
+		var r struct {
+			ID     string `json:"id"`
+			Sealed string `json:"sealed"`
+		}
+		if json.Unmarshal(raw, &r) == nil && r.ID == catalogue.BusMembershipID() {
+			return r.Sealed
+		}
+	}
+	return ""
+}