Switch: acts only on a plan moving both engine and controller, and only for value 6 (issue 1942)

cmd/mesh-controller/delivery_edges.go

@@ -50,10 +50,10 @@ type planOrder struct {
 }
 
 // switchNamed says whether a pull request's description names release 6's switch: a line that is exactly the field
-// with a value.
+// with the value 6.
 func switchNamed(body string) bool {
 	for _, line := range strings.Split(body, "\n") {
-		if rest, ok := strings.CutPrefix(strings.TrimSpace(line), switchField); ok && strings.TrimSpace(rest) != "" {
+		if rest, ok := strings.CutPrefix(strings.TrimSpace(line), switchField); ok && strings.TrimSpace(rest) == "6" {
 			return true
 		}
 	}
@@ -97,6 +97,8 @@ func orderEdges(moved []string, changes map[string]moduleChange, graph []invento
 	var out planOrder
 	sorted := append([]string(nil), moved...)
 	sort.Strings(sorted)
+	// The switch acts only on a plan that moves both the engine and the controller.
+	switchNamed = switchNamed && slices.Contains(sorted, theController) && slices.Contains(sorted, theEngine)
 	for _, server := range sorted {
 		for _, caller := range sorted {
 			if server == caller {
@@ -123,10 +125,10 @@ func orderEdges(moved []string, changes map[string]moduleChange, graph []invento
 			}
 		}
 	}
-	if switchNamed && slices.Contains(sorted, theController) && slices.Contains(sorted, theEngine) {
+	if switchNamed {
 		overruled = append(overruled, ruleEngineFirst)
 	}
-	if switchNamed && slices.Contains(sorted, theController) {
+	if switchNamed {
 		out.Together = switchSaid(overruled)
 	} else if slices.Contains(sorted, theController) && slices.Contains(sorted, theEngine) {
 		all := orderingEdges(graph, out.Edges)

cmd/mesh-controller/delivery_edges_test.go

@@ -228,7 +228,17 @@ func TestTheSwitchSaysTheEdgesItOverruled(t *testing.T) {
 
 // The switch is named by a line of a pull request's description.
 func TestTheSwitchIsNamedByAFieldOfTheDescription(t *testing.T) {
-	if !switchNamed("Fixes 1\n\nRelease-switch: 6\n") || switchNamed("Release-switch:\n") || switchNamed("about the Release-switch: 6") {
+	if !switchNamed("Fixes 1\n\nRelease-switch: 6\n") || switchNamed("Release-switch:\n") || switchNamed("Release-switch: 7") || switchNamed("about the Release-switch: 6") {
 		t.Fatal("the field is not read as a line with a value")
 	}
 }
+
+// 1942/AC3: the switch acts only on a plan that moves the engine and the controller: without mesh-host the
+// version-skew edge stays, the line present or not.
+func TestTheSwitchWithoutTheEngineKeepsVersionSkew(t *testing.T) {
+	changes := map[string]moduleChange{"app": {Manifest: true}}
+	got := orderEdges([]string{"mesh-controller", "app"}, changes, nil, true)
+	if e, ok := hasEdge(got.Edges, "app", "mesh-controller"); !ok || e.Why != "version skew" || got.Together != "" {
+		t.Fatalf("version skew lost without the engine: %+v", got)
+	}
+}