refactor: use cinc-api v0.15.1's scalar attribute and server message helpers

apps/cinc/cmd/acl.go

@@ -282,8 +282,10 @@ func explainACLChangeError(err error, grant bool, target, members string, groups
 // error itself when it isn't a server response.
 func serverMessage(err error) string {
 	var resp *cinc.ErrorResponse
-	if errors.As(err, &resp) && len(resp.Messages) > 0 {
-		return strings.Join(resp.Messages, "; ")
+	if errors.As(err, &resp) {
+		if msg := resp.ServerMessage(); msg != "" {
+			return msg
+		}
 	}
 	return err.Error()
 }

apps/cinc/cmd/node.go

@@ -3,6 +3,8 @@ package cmd
 import (
 	"bufio"
 	"fmt"
+	"maps"
+	"slices"
 	"strings"
 	"text/tabwriter"
 	"time"
@@ -581,10 +583,33 @@ func nodeSSHHost(node *cinc.Node, attr string) (string, error) {
 	if attr == "name" {
 		return node.Name, nil
 	}
-	if _, ok := node.Attribute(attr); !ok {
+	value, ok := node.Attribute(attr)
+	if !ok {
 		return "", fmt.Errorf("node %q has no %q attribute to connect to. Pick another with --attribute, or pass --attribute name to use the node name", node.Name, attr)
 	}
-	return node.AttributeString(attr), nil
+	host, ok := node.AttributeScalar(attr)
+	if !ok {
+		return "", fmt.Errorf("node %q's %q attribute isn't a single value we can connect to%s", node.Name, attr, nestedAttributeHint(attr, value))
+	}
+	return host, nil
+}
+
+// nestedAttributeHint suggests dotted paths into an attribute that holds an
+// object, e.g. "; try --attribute cloud.public_hostname".
+func nestedAttributeHint(attr string, value any) string {
+	m, ok := value.(map[string]any)
+	if !ok || len(m) == 0 {
+		return ""
+	}
+	keys := slices.Sorted(maps.Keys(m))
+	if len(keys) > 3 {
+		keys = keys[:3]
+	}
+	paths := make([]string, len(keys))
+	for i, k := range keys {
+		paths[i] = attr + "." + k
+	}
+	return "; it holds an object, so name a key inside it, such as --attribute " + strings.Join(paths, " or ")
 }
 
 func remoteOptions(flags nodeSSHFlags) remote.SSHOptions {

apps/cinc/cmd/node_test.go

@@ -922,3 +922,21 @@ func TestNodeSSHTargetsReportsUndecodableRow(t *testing.T) {
 		t.Errorf("node ssh error = %v, want the decode failure", err)
 	}
 }
+
+// An attribute that holds an object can't be a host to connect to. Before,
+// its Go map text ("map[...]") went to SSH as the host name.
+func TestNodeSSHHostRejectsNonScalarAttribute(t *testing.T) {
+	node := &cinc.Node{Name: "web01", Automatic: cinc.Attributes{"cloud": map[string]any{"public_hostname": "web01.cloud.test"}}}
+	_, err := nodeSSHHost(node, "cloud")
+	if err == nil {
+		t.Fatal("want an error for an attribute that holds an object")
+	}
+	for _, want := range []string{"web01", `"cloud"`, "cloud.public_hostname"} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("error %q should mention %s", err, want)
+		}
+	}
+	if strings.Contains(err.Error(), "map[") {
+		t.Errorf("error %q leaks Go map formatting", err)
+	}
+}