Prove Conn offers no Serve by reflection, and build its AC3 test account through ReadAccount (issue 1171, review round 1 findings 3 and 4)

go/process/conn_integration_test.go

@@ -11,7 +11,10 @@ import (
 	"crypto/x509"
 	"crypto/x509/pkix"
 	"encoding/hex"
+	"encoding/json"
 	"math/big"
+	"os"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -61,16 +64,34 @@ func selfSignedServer(t *testing.T) (url, fingerprint string) {
 	return s.ClientURL(), fingerprint
 }
 
-func mailSenderAccount(url, fingerprint string) Account {
-	return Account{URL: url, Fingerprint: fingerprint, Node: "novox", Module: "mesh-mail",
-		User: "novox.mesh-mail.send", Password: "the-pw"}
+// mailSenderAccount is the account novox.mesh-mail.send would be delivered as, the module's own secret
+// broker-send: written to a file and read back through ReadAccount (1171/AC2), exactly as a process
+// reads it, rather than built by hand.
+func mailSenderAccount(t *testing.T, url, fingerprint string) Account {
+	t.Helper()
+	data, err := json.Marshal(map[string]any{
+		"url": url, "fingerprint": fingerprint, "node": "novox", "module": "mesh-mail",
+		"user": "novox.mesh-mail.send", "password": "the-pw",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	path := filepath.Join(t.TempDir(), "broker-send")
+	if err := os.WriteFile(path, data, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	account, err := ReadAccount(path)
+	if err != nil {
+		t.Fatalf("ReadAccount on a well-formed file: %v", err)
+	}
+	return account
 }
 
 // 1171/AC3: given a test bus with TLS and the account composed for novox.mesh-mail.send, when the package
 // connects with the file, then it connects with the inbox prefix _INBOX.novox.mesh-mail.send.
 func TestConnectPinsTheFingerprintAndSetsTheInboxPrefix(t *testing.T) {
 	url, fingerprint := selfSignedServer(t)
-	account := mailSenderAccount(url, fingerprint)
+	account := mailSenderAccount(t, url, fingerprint)
 	conn, err := Connect(account)
 	if err != nil {
 		t.Fatalf("connecting with the right fingerprint was refused: %v", err)
@@ -87,7 +108,7 @@ func TestConnectPinsTheFingerprintAndSetsTheInboxPrefix(t *testing.T) {
 // 1171/AC3: connecting with a fingerprint that is not the bus's own leaf certificate is refused.
 func TestConnectRefusesTheWrongFingerprint(t *testing.T) {
 	url, _ := selfSignedServer(t)
-	account := mailSenderAccount(url, "sha256:0000000000000000000000000000000000000000000000000000000000000000")
+	account := mailSenderAccount(t, url, "sha256:0000000000000000000000000000000000000000000000000000000000000000")
 	if _, err := Connect(account); err == nil {
 		t.Fatal("connecting with the wrong fingerprint was not refused")
 	}

go/process/no_serve_test.go

@@ -0,0 +1,37 @@
+package process
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/nats-io/nats.go"
+)
+
+// 1171/AC3: it offers no Serve and no way to serve a tool — a process reaches the bus only as itself, and
+// never answers a call. Checked by reflection over *Conn's whole method set and field list, so a later
+// addition cannot bring one back without this test naming it.
+func TestConnOffersNoServeAndExposesNoRawConnection(t *testing.T) {
+	ptrType := reflect.TypeOf(&Conn{})
+	for _, forbidden := range []string{"Serve", "ServeOn", "Handle", "Subscribe", "Respond", "Answer"} {
+		if _, ok := ptrType.MethodByName(forbidden); ok {
+			t.Errorf("*Conn has a method %s: a process offers no way to serve a tool", forbidden)
+		}
+	}
+
+	natsConnType := reflect.TypeOf(&nats.Conn{})
+	structType := reflect.TypeOf(Conn{})
+	for i := 0; i < structType.NumField(); i++ {
+		f := structType.Field(i)
+		if f.IsExported() && (f.Type == natsConnType || f.Type == natsConnType.Elem()) {
+			t.Errorf("Conn exposes its raw connection through the exported field %s", f.Name)
+		}
+	}
+	for i := 0; i < ptrType.NumMethod(); i++ {
+		m := ptrType.Method(i)
+		for o := 0; o < m.Type.NumOut(); o++ {
+			if m.Type.Out(o) == natsConnType || m.Type.Out(o) == natsConnType.Elem() {
+				t.Errorf("*Conn.%s returns the raw *nats.Conn", m.Name)
+			}
+		}
+	}
+}