mesh-config resolves the values of every module the catalogue's placement or the controller's assignments name on a node, while both stand (issue 1126, ADR 0549 §3, §5, C1)

modules/mesh-config/cmd/mesh-config/main.go

@@ -115,7 +115,7 @@ func resolving(c *Config) {
 		}
 		return nil
 	}
-	for _, read := range []string{AssignmentsRead, DeclaredConfigRead, PredefinedRead} {
+	for _, read := range []string{AssignmentsRead, PlacementRead, DeclaredConfigRead, PredefinedRead} {
 		go func(read string) {
 			for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
 				time.Sleep(wait)

modules/mesh-config/cmd/mesh-config/pulled_in_test.go

@@ -21,4 +21,16 @@ func TestAModulePulledInHasItsValuesResolvedOnItsNode(t *testing.T) {
 	if r, _ := c.Reconcile(); len(r.Moved) != 4 || !r.Moved[0].Gone {
 		t.Errorf("a module no longer pulled in moved %+v", r.Moved)
 	}
+
+	// 1126 (ADR 0549 §3, §5): a module the catalogue's placement names on a node resolves there as an assigned one does,
+	// while the two sources stand; it goes when neither names it.
+	m.mirror(t, PlacementRead, "placement.ace", `{"v":1,"node":"ace","modules":[{"module":"dunst"}]}`)
+	if r, err := c.Reconcile(); err != nil || len(r.Moved) != 4 {
+		t.Fatalf("a placed module's values moved %+v (%v)", r.Moved, err)
+	}
+	expect(t, m, "ace", "10", SourceDefault)
+	_ = m.Delete(PlacementRead, "placement.ace")
+	if r, _ := c.Reconcile(); len(r.Moved) != 4 || !r.Moved[0].Gone {
+		t.Errorf("a module no longer placed moved %+v", r.Moved)
+	}
 }

modules/mesh-config/cmd/mesh-config/resolve.go

@@ -20,7 +20,10 @@ const (
 	PredefinedState = "predefined"
 	ProposalsState  = "proposals"
 
-	AssignmentsRead    = "mesh-controller.assignments"
+	AssignmentsRead = "mesh-controller.assignments"
+	// PlacementRead is the indexer's placement, read from the catalogue at each merge (novox/hq ADR 0549 §2, §3): each
+	// node's key `placement.<node>` with the modules placed there.
+	PlacementRead      = "mesh-delivery-indexer.placement"
 	DeclaredConfigRead = "mesh-controller.declared-config"
 	PredefinedRead     = "mesh-controller.predefined"
 

modules/mesh-config/cmd/mesh-config/sources.go

@@ -27,6 +27,38 @@ func (c *Config) sources() (Sources, error) {
 	}); err != nil {
 		return s, fmt.Errorf("the assignments cannot be read: %w", err)
 	}
+	// And every module the catalogue's placement names on a node (ADR 0549 §3): until ADR 0547's third milestone both
+	// sources stand (ADR 0549 §5), so a pair either names is resolved, and none loses its values while the two differ.
+	// Placement that cannot be read yet (the indexer's state not on the bus) leaves the assignments alone, said.
+	standing := map[string]bool{}
+	for _, a := range s.Assignments {
+		standing[a.Node+"."+a.Module] = true
+	}
+	if err := c.each(PlacementRead, func(key string, raw []byte) error {
+		node, ok := strings.CutPrefix(key, "placement.")
+		if !ok {
+			return nil
+		}
+		var p struct {
+			Node    string `json:"node"`
+			Modules []struct {
+				Module string `json:"module"`
+			} `json:"modules"`
+		}
+		if err := json.Unmarshal(raw, &p); err != nil || p.Node != node {
+			problems = append(problems, fmt.Sprintf("the placement %s is not one", key))
+			return nil
+		}
+		for _, m := range p.Modules {
+			if m.Module != "" && !standing[node+"."+m.Module] {
+				standing[node+"."+m.Module] = true
+				s.Assignments = append(s.Assignments, Assignment{Node: node, Module: m.Module})
+			}
+		}
+		return nil
+	}); err != nil {
+		problems = append(problems, fmt.Sprintf("the catalogue's placement cannot be read, so the assignments alone are resolved: %v", err))
+	}
 	if err := c.each(DeclaredConfigRead, func(key string, raw []byte) error {
 		m, err := ParseModuleDeclarations(raw)
 		if err != nil {

modules/mesh-config/module.json

@@ -29,6 +29,7 @@
   ],
   "reads": [
     "mesh-controller.assignments",
+    "mesh-delivery-indexer.placement",
     "mesh-controller.declared-config",
     "mesh-controller.predefined"
   ],