Fix 9.7a: the grants part resolves a read naming a seat to its holder

Builds: design 47 G A-116 (§636, §616)

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/mesh-grants/grants_test.go

@@ -4964,6 +4964,39 @@ func TestTheGrantsPartKeepsWhatEachNodeRuns(t *testing.T) {
 	}
 }
 
+// A module reading a seat holder's state, `seat:<seat>.<state>`, is granted the read of the module holding the seat on record
+// (design 47 G A-116).
+func TestASeatNamedReadIsResolvedToItsHolder(t *testing.T) {
+	for _, row := range []struct {
+		name, holder string
+		reads, want  []string
+	}{
+		{"resolved to the holder on record", "prov-one", []string{"seat:mesh-provisioner.plans", "mesh-vault.node-logins"},
+			[]string{"prov-one.plans", "mesh-vault.node-logins"}},
+		{"a new holder is read with no change of the manifest", "prov-two", []string{"seat:mesh-provisioner.provisions"},
+			[]string{"prov-two.provisions"}},
+		{"no holder on record stays as written", "", []string{"seat:mesh-provisioner.plans"}, []string{"seat:mesh-provisioner.plans"}},
+	} {
+		t.Run(row.name, func(t *testing.T) {
+			in := grants.Inputs{Nodes: []string{"a"}, Assigned: map[string][]string{"a": {"mod-t"}},
+				Manifests: map[string]catalogue.Manifest{"mod-t": {Module: "mod-t", Version: "1", RunsAs: "mod-t", Reads: row.reads,
+					OwnSecrets: catalogue.OwnSecrets{"broker": {Path: "/var/lib/mod-t/broker"}}}}}
+			if row.holder != "" {
+				in.Placed = map[string]meshmoduleassigner.Assignments{"a": {Node: "a",
+					Holds: []meshmoduleassigner.Holding{{Claim: "mesh-provisioner", Scope: "mesh", Module: row.holder}}}}
+			}
+			recs, _ := grants.ListRecords(in)
+			var got []string
+			for _, d := range recs.Assigned["a"] {
+				got = d.Reads
+			}
+			if !slices.Equal(got, row.want) {
+				t.Errorf("reads = %v, want %v", got, row.want)
+			}
+		})
+	}
+}
+
 // A module naming a seat's view, `seat:<seat>.views.<state>`, is granted the view of the module holding the seat on record, so a
 // new holder is granted with no change of its manifest (design 47 G §616).
 func TestASeatNamedViewIsResolvedToItsHolder(t *testing.T) {

modules/mesh-grants/internal/grants/records.go

@@ -88,6 +88,7 @@ func records(in Inputs, union bool) (buscompose.Records, []Gap) {
 			}
 			declare := func(m catalogue.Manifest) buscompose.Declared {
 				m.Consumes = resolveSeatViews(m.Consumes, holders)
+				m.Reads = resolveSeatReads(m.Reads, holders)
 				d := declaredFor(m, seats, declarers)
 				if len(in.Placed) > 0 {
 					d.Holds = heldWherePlaced(d.Holds, holders, node, m.Module)
@@ -212,6 +213,36 @@ func resolveSeatViews(consumes []string, holders []catalogue.Held) []string {
 	return out
 }
 
+// resolveSeatReads resolves each `seat:<seat>.<state>` of a module's reads to `<holder>.<state>`, the module holding the seat
+// on record, as resolveSeatViews does a view: a new holder is read with no change of the manifest (design 47 G A-116). An entry
+// whose seat has no holder on record stays as written, and grants nothing. Pure.
+func resolveSeatReads(reads []string, holders []catalogue.Held) []string {
+	var out []string
+	for i, r := range reads {
+		rest, isSeat := strings.CutPrefix(r, seatViewConsume)
+		seatName, state, named := strings.Cut(rest, ".")
+		if !isSeat || !named || state == "" || strings.Contains(state, ".") {
+			if out != nil {
+				out = append(out, r)
+			}
+			continue
+		}
+		if out == nil {
+			out = slices.Clone(reads[:i])
+		}
+		holder := slices.IndexFunc(holders, func(h catalogue.Held) bool { return sameSeat(h.Claim, seatName) })
+		if holder < 0 {
+			out = append(out, r)
+			continue
+		}
+		out = append(out, holders[holder].Module+"."+state)
+	}
+	if out == nil {
+		return reads
+	}
+	return out
+}
+
 // consumedOf splits what a manifest consumes as the composer grants it: a seat's event on the seat's own subject (its
 // watches), every other by its emitter's (novox/hq ADR 0118). A placed module and the node-engine's own manifest are split
 // alike.