A module in InOwn wanted at a build of the new form has its build taken in: the reader and the composition fold by one rule (issue 1585)

frombus skipped reading the build of every module in Scope.InOwn, while compose.compositions folds such a module only
at no src2: fingerprint: a want at src2: (nats on novox, its have waiting for a yes) composed it from the indexer's
unresolved manifest and built() refused it, "no build has published" its server artifact. compose.Folds is now the one
rule; frombus takes the build in, or keeps the module at its wanted build, exactly where it says the module is not
folded. A row composes spiegel, in InOwn and wanted at src2:, from its build's upstream image; it read the indexer's
manifest before.

Claude-Session: https://claude.ai/code/session_01JG73KG7AfSdh6FP8VrBqCn

internal/compose/composed.go

@@ -63,6 +63,15 @@ func CompositionsIn(in Input, node string, fps map[string]string, mode Mode) (ou
 	return compositions(in, node, fps, mode, false)
 }
 
+// Folds says whether a module the node runs inside its own composition (inOwn, Node.InOwn) is folded there at the
+// fingerprint fp it is composed at: only at no fingerprint of the new form. At one (src2:) it has a composition of its
+// own, composed from its build, so every reader of a build (frombus) takes the build in exactly where this says it is
+// not folded (issue 1585: nats on novox, folded by the reader and composed at src2: here, refused for its server
+// artifact no build had published).
+func Folds(inOwn bool, fp string) bool {
+	return inOwn && !strings.HasPrefix(fp, delivery.SourcePrefix2)
+}
+
 func compositions(in Input, node string, fps map[string]string, mode Mode, applied bool) (out map[string]delivery.Composed, skipped, stood []string, err error) {
 	reading := in
 	reading.Nodes = append([]Node(nil), in.Nodes...)
@@ -84,7 +93,7 @@ func compositions(in Input, node string, fps map[string]string, mode Mode, appli
 	// The private network's module is built by nobody: no fingerprint of the new form ever names it.
 	inOwn[overlay.Name] = true
 	folds := func(module string) bool {
-		return module != "" && inOwn[module] && !strings.HasPrefix(fps[module], delivery.SourcePrefix2)
+		return module != "" && Folds(inOwn[module], fps[module])
 	}
 	if !found {
 		return nil, nil, nil, fmt.Errorf("compose: the mesh has no node %q", node)

internal/compose/frombus/answer_rows_test.go

@@ -191,6 +191,28 @@ func answerNamesEveryRefusalAndLeavesAnOldBuildToTheNode(t *testing.T) {
 		!strings.Contains(held["spiegel"], "spiegel has not been built for this mesh") {
 		t.Errorf("composed spiegel without what runs: %v %v, want spiegel held alone", err, held)
 	}
+	// Issue 1585 (nats on novox, met twice): wanted at a build of the new form, a module in InOwn is no longer folded
+	// (compose.Folds), so its build is taken in and it composes with its image, never from the indexer's manifest as
+	// "not built for this mesh".
+	{
+		bb := mk("lemurs", overlay.Name, "spiegel")
+		bp := bb.placements["n1"]
+		bp.Decided.Endpoint = "n1.example:51820"
+		bb.placements["n1"] = bp
+		sp := bb.modules["spiegel"]
+		sp.FP2 = fp("3")
+		bb.modules["spiegel"] = sp
+		image := "registry.example:5100/spiegel/site@sha256:" + strings.Repeat("7", 64)
+		bb.builds["spiegel "+sp.FP2] = &delivery.BuilderBuild{State: delivery.BuildDone, Manifest: sp.Manifest,
+			Artifacts: []delivery.BuiltArtifact{{Name: "site", Kind: "upstream", Reference: image, Digest: "sha256:" + strings.Repeat("7", 64)}}}
+		read, err := ComposingInput(ctx, bb, Mesh{}, Scope{Node: "n1", InOwn: []string{"spiegel"}},
+			map[string]string{"lemurs": fp("e"), "spiegel": sp.FP2})
+		raw, _ := json.Marshal(read.Catalogue["spiegel"])
+		if err != nil || read.ComposedHow.Held["spiegel"] != "" || !strings.Contains(string(raw), strings.Repeat("7", 64)) {
+			t.Errorf("spiegel in InOwn wanted at %s: %v, held %v, read as %s; want its build's image", sp.FP2, err,
+				read.ComposedHow, raw)
+		}
+	}
 
 	// (C) Issue 1126, C5: what the others read of a module carried as it runs is what runs, never its stub's: the filter
 	// opens the machine port its running container publishes (de-spiegel's 20005 on novox, not its software's 8080; a

internal/compose/frombus/frombus.go

@@ -876,7 +876,7 @@ func fromBuilds(ctx context.Context, r Reader, build func(ctx context.Context, m
 	keptAt := maps.Clone(s.KeptAt)
 	for _, pm := range p.Modules {
 		if m, ok := modules[pm.Module]; ok && m.FP2 != "" && wanted[pm.Module] != "" && wanted[pm.Module] != m.FP2 &&
-			keptAt[pm.Module] == "" && !slices.Contains(s.InOwn, pm.Module) {
+			keptAt[pm.Module] == "" && !compose.Folds(slices.Contains(s.InOwn, pm.Module), wanted[pm.Module]) {
 			if keptAt == nil {
 				keptAt = map[string]string{}
 			}
@@ -891,9 +891,10 @@ func fromBuilds(ctx context.Context, r Reader, build func(ctx context.Context, m
 	}
 	for _, pm := range p.Modules {
 		m, ok := modules[pm.Module]
-		if !ok || m.FP2 == "" || keptAt[pm.Module] != "" || slices.Contains(s.InOwn, pm.Module) {
-			// A module it runs inside its own composition is composed there as before: no build of the new form is what
-			// it runs (Scope.InOwn).
+		if !ok || m.FP2 == "" || keptAt[pm.Module] != "" || compose.Folds(slices.Contains(s.InOwn, pm.Module), wanted[pm.Module]) {
+			// A module it runs inside its own composition is composed there as before while it is folded: no build of the
+			// new form is what it runs (Scope.InOwn). Wanted at a build of the new form it is no longer folded (compose.Folds,
+			// the composition's own rule), so its build is taken in (issue 1585).
 			continue
 		}
 		if _, refused := in.Refused[pm.Module]; refused {