Say a layer whole where the mesh reports it, and give tests their placement (issue 651)

The facts snapshot, the take preview and the settings history read a layer as it
was set; tests that place give the layer through LayerOf.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/mesh-controller/adoption.go

@@ -424,8 +424,9 @@ func comparisonOf(module string, c comparison, opts takeOptions) (preview string
 	}
 	// And its settings on this machine, composed against its definition (rule 1, rule 6).
 	for _, layer := range c.layers {
-		keys := make([]string, 0, len(layer.Values))
-		for k := range layer.Values {
+		said := layer.Whole()
+		keys := make([]string, 0, len(said))
+		for k := range said {
 			keys = append(keys, k)
 		}
 		sort.Strings(keys)

cmd/mesh-controller/facts.go

@@ -348,11 +348,11 @@ func gatherFacts(ctx context.Context, open *stores, busVersion string) (snapshot
 				if layer.From == catalogue.MeshWideLayer {
 					if !meshWide[module] {
 						meshWide[module] = true
-						f.Settings = append(f.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Values)})
+						f.Settings = append(f.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Whole())})
 					}
 					continue
 				}
-				m.Settings = append(m.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Values)})
+				m.Settings = append(m.Settings, snapshot.Settings{Module: module, Values: scrub.Values(layer.Whole())})
 			}
 		}
 		m.Declaration = declarationFacts(ctx, open, n.Name, gens, gensErr, scrub)

cmd/mesh-controller/mesh_for_test.go

@@ -33,7 +33,21 @@ import (
 func aMesh(t *testing.T) *stores {
 	t.Helper()
 	inventory.ForTest(t) // raises the store, migrates it, and points the environment at it
-	licences.ForTest(t)  // planning reaches this one too, by name and never by connection
+	return aMeshOnTheStore(t)
+}
+
+// aMeshBefore is aMesh on a store migrated only below migration `number`, with the function that runs the
+// rest: for a test of what a migration that moves data does to what the mesh composes (novox/hq issue 651).
+func aMeshBefore(t *testing.T, number int) (*stores, func()) {
+	t.Helper()
+	_, migrate := inventory.ForTestBefore(t, number)
+	return aMeshOnTheStore(t), migrate
+}
+
+// aMeshOnTheStore is the mesh aMesh makes, on the store the environment points at.
+func aMeshOnTheStore(t *testing.T) *stores {
+	t.Helper()
+	licences.ForTest(t) // planning reaches this one too, by name and never by connection
 
 	open, err := openStores(t.Context())
 	if err != nil {

cmd/mesh-controller/modules.go

@@ -537,6 +537,10 @@ func settingsCommand(ctx context.Context, args []string) error {
 				if p.SetBy != "" {
 					by = "; " + p.SetBy
 				}
+				if p.Why != "" {
+					// A layer whose placement moved out of it (migration 0097): still the layer, as it stands.
+					by += "; " + p.Why
+				}
 				fmt.Printf("%s on %s, until %s (%s%s):\n  %s\n", positionals[0], where,
 					p.ReplacedAt.Local().Format("2006-01-02 15:04:05"), p.ReplacedBy, by, shown)
 			}