Let root-free take its machines as a list, as the router names them

The router's contract names the machines as a JSON array. A verb's argument declared a list now takes
an array of names (or one text separated by commas), and refuses anything else in it.

cmd/mesh-controller/probe_agent_root_test.go

@@ -181,7 +181,18 @@ func TestRootFreeIsAnsweredOnlyByTheServingController(t *testing.T) {
 	if _, err := argvFor("root-free", map[string]any{"machines": "anchor"}); err == nil {
 		t.Error("root-free ran as a command")
 	}
-	if _, err := readArguments("root-free", map[string]any{"machines": []any{"anchor"}}); err == nil {
-		t.Error("root-free took its machines as a list; they are named in one text, separated by commas")
+	// The router names its machines as a list (its contract with this verb); one text separated by commas is
+	// the same; anything else in the list is refused.
+	for _, given := range []any{[]any{"anchor", "relay"}, "anchor, relay"} {
+		a, err := readArguments("root-free", map[string]any{"machines": given})
+		if err != nil || a.given["machines"] != "anchor,relay" && a.given["machines"] != "anchor, relay" {
+			t.Errorf("root-free given %v read %v (%v)", given, a, err)
+		}
+	}
+	if _, err := readArguments("root-free", map[string]any{"machines": []any{"anchor", 7}}); err == nil {
+		t.Error("root-free took a number for a machine")
+	}
+	if _, err := readArguments("status", map[string]any{"machines": []any{"anchor"}}); err == nil {
+		t.Error("a verb that takes no list took one")
 	}
 }

cmd/mesh-controller/seatverbs.go

@@ -114,6 +114,14 @@ func declaredArguments(v catalogue.Verb) (names []string, switches map[string]bo
 	return names, switches
 }
 
+// isList says a verb's argument is declared a list of text (catalogue's listed): given as a JSON array, it is
+// read as its items joined by commas, as the same argument given as one text would be.
+func isList(v catalogue.Verb, name string) bool {
+	props, _ := v.Input["properties"].(map[string]any)
+	p, _ := props[name].(map[string]any)
+	return p != nil && p["type"] == "array"
+}
+
 // readArguments refuses what the verb does not take, before anything is composed.
 func readArguments(verb string, args map[string]any) (*verbArguments, error) {
 	v, known := controllerVerb(verb)
@@ -150,6 +158,19 @@ func readArguments(verb string, args map[string]any) (*verbArguments, error) {
 				return nil, fmt.Errorf("%s: %q is text, not true or false", verb, k)
 			}
 			value = fmt.Sprint(x)
+		case []any:
+			if !isList(v, k) {
+				return nil, fmt.Errorf("%s: %q is text, and was given a list", verb, k)
+			}
+			items := make([]string, 0, len(x))
+			for _, item := range x {
+				text, ok := item.(string)
+				if !ok || strings.TrimSpace(text) == "" || strings.Contains(text, ",") {
+					return nil, fmt.Errorf("%s: %q is a list of names, and holds %v", verb, k, item)
+				}
+				items = append(items, strings.TrimSpace(text))
+			}
+			value = strings.Join(items, ",")
 		default:
 			return nil, fmt.Errorf("%s: %q is text, and was given %T", verb, k, x)
 		}

internal/catalogue/verbs.go

@@ -435,9 +435,9 @@ var ControllerVerbs = []Verb{
 		"last 15 minutes, and the login shell's execute is not served there. Anything else, a read that failed " +
 		"included, is not free and says why. The router asks it before an answer from a channel proving its sender " +
 		"may approve. Only reads.",
-		Input: schema(map[string]string{
-			"machines": "the machines to judge, separated by commas",
-		}, []string{"machines"})},
+		Input: listed(schema(map[string]string{
+			"machines": "the machines to judge, by name: a list, or one text separated by commas",
+		}, []string{"machines"}), "machines")},
 	{Name: "dead-letters", Description: "Every message a consumer on the bus gave up on after handing it over " +
 		"as often as it may, kept in DEAD_LETTERS: whose consumer, the subject, how often it was handed over and " +
 		"when it was given up, newest first. With id: that one whole, with what it said. With deliver: hand it " +
@@ -554,6 +554,21 @@ func schema(properties map[string]string, required []string, switches ...string)
 	return out
 }
 
+// listed makes the named properties of a schema lists of text: a caller gives them as a JSON array (or, as
+// any argument, one text separated by commas).
+func listed(in map[string]any, names ...string) map[string]any {
+	props, _ := in["properties"].(map[string]any)
+	for _, n := range names {
+		p, _ := props[n].(map[string]any)
+		if p == nil {
+			panic("a list that is not a property: " + n)
+		}
+		props[n] = map[string]any{"type": "array", "items": map[string]any{"type": "string"},
+			"description": p["description"]}
+	}
+	return in
+}
+
 // unpromised is what a claim says it serves and the seat's protocol never promised.
 func unpromised(serves []string, promised []Verb) []string {
 	has := map[string]bool{}