Merge remote-tracking branch 'origin/main' into feat/the-store-seat-has-verbs

internal/catalogue/manifest.go

@@ -293,6 +293,12 @@ type Manifest struct {
 	// module claiming a seat answers what that seat's protocol promises (novox/hq ADR 0118).
 	Tools []string `json:"tools,omitempty"`
 
+	// Instances says whether this module's instances are the same anywhere — `interchangeable` —
+	// so a call that names no machine may be answered by any of them (novox/hq ADR 0160). A fact
+	// about the software, not about the bus: a stateless web tool says it; a database does not,
+	// and its instances are then each addressed by machine, never confused for one another.
+	Instances string `json:"instances,omitempty"`
+
 	// Invokes are the tools this module calls, each `<module>.<tool>` or a role's `seat:<seat>.<verb>`,
 	// or the single entry `*` for every tool on the mesh (novox/hq ADR 0152, ADR 0154).
 	//
@@ -1173,6 +1179,11 @@ func ParseManifest(raw []byte) (Manifest, error) {
 				m.Module, r))
 		}
 	}
+	if m.Instances != "" && m.Instances != InstancesInterchangeable {
+		problems = append(problems, fmt.Sprintf(
+			"%s says its instances are %q; the one word is %q, for a module that is the same on every machine",
+			m.Module, m.Instances, InstancesInterchangeable))
+	}
 	for _, offer := range m.Provides {
 		p := offer.Name
 		if !name.MatchString(p) {
@@ -1960,3 +1971,7 @@ func (o OwnSecrets) Paths() map[string]string {
 	}
 	return out
 }
+
+// InstancesInterchangeable is the one value of a definition's `instances`: the module is the same
+// on every machine, so any instance may answer for the module.
+const InstancesInterchangeable = "interchangeable"