Read the bus through a module's declared states in frombus, with the runtime's adapter in fromruntime, so mesh-provisioner and disk-load compose from one reader instead of two copies (issue 1955)

go/compose/frombus/frombus_test.go

@@ -14,6 +14,7 @@ import (
 	"os"
 	"reflect"
 	"slices"
+	"sort"
 	"strings"
 	"testing"
 
@@ -724,6 +725,17 @@ func TestInput(t *testing.T) {
 			}
 		}
 	}
+	// And the same through StatesReader, over the fake's states as a module's runtime gives them (one reader for
+	// mesh-provisioner and disk-load, the lead 2026-10-29).
+	viaStates, _, err := DataItems(ctx, StatesReader(statesOf(t, ctx, noSecrets), func(_ context.Context, url string) ([]byte, error) {
+		for _, body := range noSecrets.archives {
+			return body, nil
+		}
+		return nil, errors.New("no archive")
+	}), Mesh{}, Scope{Node: "n1"})
+	if err != nil || !reflect.DeepEqual(viaStates, items) {
+		t.Errorf("through the states the data items are %v, %v; through the reader %v", viaStates, err, items)
+	}
 
 	// And what a provider on another node serves from its settings (mailu's smtp domain, issue 1126: shanks refused
 	// '${setting:domain} ... nothing sets "domain"'): read for that provider's served keys alone, through Served.
@@ -769,3 +781,72 @@ func TestInput(t *testing.T) {
 		}
 	}
 }
+
+// mapStates are read states by name, key to value, as a module's runtime gives them.
+type mapStates map[string]map[string][]byte
+
+func (m mapStates) Get(state, key string) ([]byte, bool, error) {
+	v, ok := m[state][key]
+	return v, ok, nil
+}
+
+func (m mapStates) Keys(state string) ([]string, error) {
+	var out []string
+	for k := range m[state] {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out, nil
+}
+
+// statesOf is b laid out as the states StatesReader reads.
+func statesOf(t *testing.T, ctx context.Context, b *bus) mapStates {
+	t.Helper()
+	out := mapStates{}
+	put := func(state, key string, raw []byte, err error) {
+		if err != nil {
+			t.Fatal(err)
+		}
+		if out[state] == nil {
+			out[state] = map[string][]byte{}
+		}
+		out[state][key] = raw
+	}
+	placements, _ := b.Placements(ctx)
+	for node, p := range placements {
+		k, _ := delivery.PlacementKey(node)
+		raw, err := delivery.EncodePlacement(p)
+		put(PlacementRead, k, raw, err)
+	}
+	records, _ := b.Records(ctx)
+	for node, r := range records {
+		k, _ := delivery.HaveNodeKey(node)
+		rec := r
+		raw, err := delivery.EncodeHaveNode(delivery.HaveNode{Record: &rec})
+		put(HaveRead, k, raw, err)
+	}
+	modules, _ := b.Modules(ctx)
+	for name, m := range modules {
+		raw, err := delivery.EncodeModule(m)
+		put(ModulesRead, name, raw, err)
+		var mf struct{ Module string }
+		_ = json.Unmarshal(b.manifests[m.Manifest], &mf)
+		k, _ := delivery.ManifestsKey(m.Manifest)
+		raw, err = delivery.EncodeManifest(delivery.Manifest{Module: mf.Module, JSON: string(b.manifests[m.Manifest])})
+		put(ManifestsRead, k, raw, err)
+	}
+	for key, build := range b.builds {
+		module, fp, _ := strings.Cut(key, " ")
+		k, _ := delivery.BuilderBuildKey(module, fp)
+		raw, err := delivery.EncodeBuilderBuild(*build)
+		put(BuildsRead, k, raw, err)
+	}
+	for nm, values := range b.values {
+		for k, v := range values {
+			value, _ := json.Marshal(v)
+			raw, err := json.Marshal(map[string]any{"value": json.RawMessage(value), "source": catalogue.SourceModule})
+			put(ResolvedRead, nm+"."+k, raw, err)
+		}
+	}
+	return out
+}