Carry the machine-assigned port in a plan's contribution, so a provider serving from plans dials where the module listens (issue 774, research 072 row 34)

route-proxy served every route at the software's own port (gitea's 3000, published at 20000;
grafana's 3000 on another machine, published at 20012) and public sites answered 502. The plan's
contribution now carries the port the placement assigned, the number ${port:N} gives the module,
and a composition for plans refuses a port none assigned by module, node and port.

go/compose/render.go

@@ -58,6 +58,8 @@ func (c *composer) render(nodeName string, mode Mode) (Rendered, error) {
 	}
 	r := placed.Rendering
 	out.ForeseenPorts = placed.ForeseenPorts
+	// A plan carries its contributions' machine ports, refused where the placement assigned none (issue 774).
+	r.Planned = mode == Planning
 	r.Grants, r.Withheld, r.Unbound = grants, withheld, unbound
 	out.Withheld, out.Unbound = withheld, unbound
 	for _, g := range grantsForeseen {

go/compose/rendering.go

@@ -245,6 +245,13 @@ func (c *composer) portsFor(node Node, plan catalogue.Resolution, settings catal
 					where = at
 				} else {
 					*foreseen = append(*foreseen, fmt.Sprintf("%s:%d", m.Module, l.Port))
+					if r.Unassigned == nil {
+						r.Unassigned = map[string]map[int]bool{}
+					}
+					if r.Unassigned[m.Module] == nil {
+						r.Unassigned[m.Module] = map[int]bool{}
+					}
+					r.Unassigned[m.Module][l.Port] = true
 				}
 			}
 			if ports[m.Module] == nil {

go/compose/rendering_test.go

@@ -52,12 +52,12 @@ func TestAnAllocatedPortIsComposedAndAnUnallocatedOneIsNamedForeseenNotInvented(
 	if p := got.Rendering.Ports["web"][8080]; p != 8080 {
 		t.Errorf("a port nobody allocated is composed as %d, not as the manifest's own", p)
 	}
-	if len(got.ForeseenPorts) != 1 || got.ForeseenPorts[0] != "web:8080" {
-		t.Errorf("foreseen ports are %v", got.ForeseenPorts)
+	if len(got.ForeseenPorts) != 1 || got.ForeseenPorts[0] != "web:8080" || !got.Rendering.Unassigned["web"][8080] {
+		t.Errorf("foreseen ports are %v (unassigned %v)", got.ForeseenPorts, got.Rendering.Unassigned)
 	}
 	nodeOf(t, &in, "laptop").Ports = map[string]map[int]int{"web": {8080: 20123}}
 	got = placed(t, in, "laptop")
-	if p := got.Rendering.Ports["web"][8080]; p != 20123 || len(got.ForeseenPorts) != 0 {
+	if p := got.Rendering.Ports["web"][8080]; p != 20123 || len(got.ForeseenPorts) != 0 || got.Rendering.Unassigned != nil {
 		t.Errorf("the allocated port is composed as %d (foreseen %v)", p, got.ForeseenPorts)
 	}
 	// A port the module does not publish is not the mesh's to move, so it is never foreseen.
@@ -70,6 +70,12 @@ func TestAnAllocatedPortIsComposedAndAnUnallocatedOneIsNamedForeseenNotInvented(
 		t.Errorf("an unpublished port: %v foreseen %v", got.Rendering.Ports, got.ForeseenPorts)
 	}
 	unchanged(t, mk, func(in Input) { placed(t, in, "laptop") })
+	// Only a composition for plans refuses a contribution whose port none assigned (issue 774): a declaration still composes.
+	for _, mode := range []Mode{Reading, Foreseeing, Planning} {
+		if got := rendered(t, mk(), "laptop", mode).Rendering; got.Planned != (mode == Planning) {
+			t.Errorf("mode %d composes with Planned %v", mode, got.Planned)
+		}
+	}
 }
 
 // 1363/AC3: a port the operator gave is used, over the allocated one, and a consumer elsewhere is told it