A membership carries its module's bus-state bindings, by local name (issue 1966 S3)

ADR 0595 §1, §7: the binding travels on the bus module's created and the
grants part writes it into the membership; omitted when empty, so a
membership without bindings encodes byte for byte as before. The two
address tests are one table.

go/membership/membership.go

@@ -57,6 +57,33 @@ type Membership struct {
 	Hears   []HeardIssued  `json:"hears,omitempty"`
 	// Waits are the event families a session may wait on through the mesh MCP server (novox/hq ADR 0367 §2).
 	Waits []WaitIssued `json:"waits,omitempty"`
+	// Bindings are the module's bus state as the bus module created it, one per entry its manifest asks for in
+	// `requires` (novox/hq ADR 0595 §1, §7): written by the grants part when it hears the bus module's `created`.
+	Bindings []BusBinding `json:"bindings,omitempty"`
+}
+
+// BusBinding is one bus-state entry's names on the bus, by the local name its module asks for it by (novox/hq ADR 0595
+// §1, design 25 § 12.2): the module names only locally, and reaches its own entries, and only those, through these.
+// Which names are set follows the storage type: a stream's Stream and Subject, a key-value bucket's Bucket, an object
+// store's ObjectStore, and a ledger's History, State, Indexes and Snapshot.
+type BusBinding struct {
+	Local string `json:"local"`
+	// Storage and Template are the entry's storage type and template (catalogue.Storage…, catalogue.Template…).
+	Storage  string `json:"storage"`
+	Template string `json:"template,omitempty"`
+	// Stream and Subject are a stream's name and the subject its messages are on; Subject is also a ledger's history's.
+	Stream  string `json:"stream,omitempty"`
+	Subject string `json:"subject,omitempty"`
+	// Bucket is a key-value bucket's name.
+	Bucket string `json:"bucket,omitempty"`
+	// ObjectStore is an object store's name.
+	ObjectStore string `json:"object-store,omitempty"`
+	// Ledger, for the storage type ledger: its history stream (one subject per instance), its state bucket, each
+	// declared index's bucket by index name, and the subject of the instances' snapshots (ADR 0597 §1, §4, §8).
+	History  string            `json:"history,omitempty"`
+	State    string            `json:"state,omitempty"`
+	Indexes  map[string]string `json:"indexes,omitempty"`
+	Snapshot string            `json:"snapshot,omitempty"`
 }
 
 // Served is one address a tool is answered on.

go/membership/membership_test.go

@@ -6,31 +6,22 @@ import (
 	"testing"
 )
 
+// A credential is read out of a bus address, and the bare address carries no credential and a scheme.
 func TestACredentialIsReadOutOfABusAddress(t *testing.T) {
-	for _, c := range []struct{ in, user, password, bare string }{
-		{"nats://controller:secret@127.0.0.1:4222", "controller", "secret", "nats://127.0.0.1:4222"},
-		{"controller:secret@127.0.0.1:4222", "controller", "secret", "127.0.0.1:4222"},
-		{"nats://127.0.0.1:4222", "", "", "nats://127.0.0.1:4222"},
-		{"127.0.0.1:4222", "", "", "127.0.0.1:4222"},
+	for _, c := range []struct{ in, user, password, bare, schemed string }{
+		{"nats://controller:secret@127.0.0.1:4222", "controller", "secret", "nats://127.0.0.1:4222", "nats://127.0.0.1:4222"},
+		{"controller:secret@127.0.0.1:4222", "controller", "secret", "127.0.0.1:4222", "nats://127.0.0.1:4222"},
+		{"nats://127.0.0.1:4222", "", "", "nats://127.0.0.1:4222", "nats://127.0.0.1:4222"},
+		{"127.0.0.1:4222", "", "", "127.0.0.1:4222", "nats://127.0.0.1:4222"},
 		// A password containing an at-sign: split on the last one.
-		{"nats://controller:a@b@127.0.0.1:4222", "controller", "a@b", "nats://127.0.0.1:4222"},
+		{"nats://controller:a@b@127.0.0.1:4222", "controller", "a@b", "nats://127.0.0.1:4222", "nats://127.0.0.1:4222"},
 	} {
 		user, password, bare := CredentialIn(c.in)
 		if user != c.user || password != c.password || bare != c.bare {
 			t.Errorf("%q read as %q/%q at %q; wanted %q/%q at %q", c.in, user, password, bare, c.user, c.password, c.bare)
 		}
-	}
-}
-
-func TestABareAddressCarriesNoCredentialAndAScheme(t *testing.T) {
-	for in, want := range map[string]string{
-		"nats://controller:secret@10.0.0.1:4222": "nats://10.0.0.1:4222",
-		"controller:secret@10.0.0.1:4222":        "nats://10.0.0.1:4222",
-		"nats://10.0.0.1:4222":                   "nats://10.0.0.1:4222",
-		"10.0.0.1:4222":                          "nats://10.0.0.1:4222",
-	} {
-		if got := BareAddress(in); got != want {
-			t.Errorf("BareAddress(%q) = %q, want %q", in, got, want)
+		if got := BareAddress(c.in); got != c.schemed {
+			t.Errorf("BareAddress(%q) = %q, want %q", c.in, got, c.schemed)
 		}
 	}
 }
@@ -66,6 +57,24 @@ func TestAMembershipRoundTripsAsIssued(t *testing.T) {
 	if !reflect.DeepEqual(in, out) {
 		t.Fatalf("round trip changed it:\n%+v\n%+v", in, out)
 	}
+	// 1966/AC4: a membership with a ledger binding round-trips; one without bindings encodes as before, byte for byte.
+	bound := in
+	bound.Bindings = []BusBinding{{Local: "records", Storage: "ledger", Template: "ledger", History: "forge_records",
+		Subject: "forge_records.>", State: "forge_records_state", Indexes: map[string]string{"search": "forge_records_search"},
+		Snapshot: "forge_records_snapshot.>"}}
+	boundRaw, err := json.Marshal(bound)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var boundBack Membership
+	if err := json.Unmarshal(boundRaw, &boundBack); err != nil || !reflect.DeepEqual(bound, boundBack) {
+		t.Fatalf("a membership with a ledger binding read back as %+v (%v)", boundBack, err)
+	}
+	before, _ := json.Marshal(Membership{Node: "ace", Module: "forge", Tools: "t", Emits: "e", Serves: []Served{{Subject: "s"}},
+		State: []StateIssued{{Name: "repos", Bucket: "forge_repos", Writes: true}}})
+	if string(before) != `{"node":"ace","module":"forge","serves":[{"subject":"s"}],"emits":"e","tools":"t","state":[{"name":"repos","bucket":"forge_repos","writes":true}]}` {
+		t.Fatalf("a membership without bindings encodes otherwise than before: %s", before)
+	}
 	var wire map[string]json.RawMessage
 	_ = json.Unmarshal(raw, &wire)
 	for _, k := range []string{"receives", "mesh", "seat-traffic"} {