Pin the node-engine at its ADR 0328 merge (#95), and speak its contract: a library's verdict is said for the modules that use it

internal/catalogue/libraries.go

@@ -468,6 +468,7 @@ type Joined struct {
 	Primary    string
 	PrimaryGID int
 	Added      []string
+	AddedGIDs  []int
 }
 
 // librariesOf is the libraries a module uses, by name, in the order its entries first name them.
@@ -504,6 +505,7 @@ func joinedOf(m Manifest, with Rendering) (Joined, error) {
 			continue
 		}
 		j.Added = append(j.Added, MeshName(lib))
+		j.AddedGIDs = append(j.AddedGIDs, gid)
 	}
 	return j, nil
 }
@@ -723,14 +725,15 @@ type GroupEntry struct {
 	GID  int    `json:"gid"`
 }
 
-// IdentityEntry is one joining module's user as a machine's declaration names it (§4): its own group has its uid,
-// and Groups are its library groups, the primary first.
+// IdentityEntry is one joining module's user as a machine's declaration names it (§4; mesh-host internal/declaration
+// Identity): the engine always makes its own group with its uid; GID is its primary group's number — its first
+// library's, or its own — and Groups the numbers of its added groups.
 type IdentityEntry struct {
-	Module string   `json:"module"`
-	Name   string   `json:"name"`
-	UID    int      `json:"uid"`
-	GID    int      `json:"gid"`
-	Groups []string `json:"groups,omitempty"`
+	Module string `json:"module"`
+	Name   string `json:"name"`
+	UID    int    `json:"uid"`
+	GID    int    `json:"gid"`
+	Groups []int  `json:"groups,omitempty"`
 }
 
 // libraryEnvelope is what a machine's declaration says of libraries and joining modules: the group of every library
@@ -748,10 +751,8 @@ func (r Resolution) libraryEnvelope(with Rendering, joined []Joined) ([]GroupEnt
 	sort.Slice(groups, func(i, j int) bool { return groups[i].Name < groups[j].Name })
 	var ids []IdentityEntry
 	for _, j := range joined {
-		e := IdentityEntry{Module: j.Module, Name: IdentityName(j.Module), UID: j.UID, GID: j.UID}
-		if j.Primary != IdentityName(j.Module) {
-			e.Groups = append([]string{j.Primary}, j.Added...)
-		}
+		e := IdentityEntry{Module: j.Module, Name: IdentityName(j.Module), UID: j.UID, GID: j.PrimaryGID,
+			Groups: append([]int(nil), j.AddedGIDs...)}
 		ids = append(ids, e)
 	}
 	sort.Slice(ids, func(a, b int) bool { return ids[a].Module < ids[b].Module })