issue 1840/S3: keep each node's declared packages on the bus, so the pacman verbs can say what a node declares

cmd/mesh-controller/record_mirrors.go

@@ -7,6 +7,7 @@ import (
 	"sort"
 	"time"
 
+	"git.novox.be/novox/mesh-sdk/go/compose"
 	"github.com/nats-io/nats.go"
 	"github.com/nats-io/nats.go/jetstream"
 
@@ -29,7 +30,7 @@ import (
 const mirrorEvery = 10 * time.Second
 
 // mirroringRecords keeps the mirrors current for as long as this controller serves: ctx ends when it stops.
-func mirroringRecords(ctx context.Context, inv *inventory.Inventory, conn *nats.Conn, announce recordmirror.Announcer) {
+func mirroringRecords(ctx context.Context, open *stores, inv *inventory.Inventory, conn *nats.Conn, announce recordmirror.Announcer) {
 	api, err := jetstream.New(conn)
 	if err != nil {
 		fmt.Printf("the record mirrors are not kept: %v\n", err)
@@ -44,8 +45,9 @@ func mirroringRecords(ctx context.Context, inv *inventory.Inventory, conn *nats.
 		return e
 	}
 	sources := map[string]func(context.Context) (map[string][]byte, error){
-		recordmirror.DeclaredConfig.Name: inv.DeclaredConfigMirror,
-		recordmirror.Predefined.Name:     inv.PredefinedMirror,
+		recordmirror.DeclaredConfig.Name:   inv.DeclaredConfigMirror,
+		recordmirror.Predefined.Name:       inv.PredefinedMirror,
+		recordmirror.DeclaredPackages.Name: declaredPackagesMirror(open),
 	}
 	writers := map[string]*recordmirror.Writer{}
 	failing := map[string]string{}
@@ -176,3 +178,36 @@ func keepingAssignments(ctx context.Context, inv *inventory.Inventory, announce
 	}
 	events.known = now
 }
+
+// declaredPackagesMirror is the source of the declared-packages mirror (ADR 0507 §5): each node's composition, asked as a
+// question that makes nothing, and the packages it declares with the modules that declare them. A node whose own set does
+// not compose has no key, and any other failure to read is the pass's error, so a key is never purged for a store that
+// could not be read.
+func declaredPackagesMirror(open *stores) func(context.Context) (map[string][]byte, error) {
+	return func(ctx context.Context) (map[string][]byte, error) {
+		in, err := inputFor(ctx, open)
+		if err != nil {
+			return nil, err
+		}
+		// Which module owns each resource is carried only for a node-engine that reads it, so every node is asked as one that does.
+		asked := in.Input
+		asked.Nodes = append([]compose.Node(nil), in.Nodes...)
+		for i := range asked.Nodes {
+			asked.Nodes[i].ReadsModules = true
+		}
+		out := map[string][]byte{}
+		for _, n := range in.sortedNodes() {
+			d, _, err := compose.ComposeIn(asked, n.Name, compose.Foreseeing)
+			if compose.IsUnresolvable(err) {
+				continue
+			}
+			if err != nil {
+				return nil, fmt.Errorf("the packages %s declares cannot be read: %w", n.Name, err)
+			}
+			if out[n.Name], err = inventory.DeclaredPackagesValue(n.Name, d.Resources, d.ModuleOf); err != nil {
+				return nil, err
+			}
+		}
+		return out, nil
+	}
+}