all: update the tsd.System constructor name (#15372)

Replace NewSystemWithEventBus with plain NewSystem, and update all usage.
See https://github.com/tailscale/tailscale/pull/15355#discussion_r2003910766

Updates #15160

Change-Id: I64d337f09576b41d9ad78eba301a74b9a9d6ebf4
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -376,7 +376,7 @@ func run() (err error) {
 
 	// Install an event bus as early as possible, so that it's
 	// available universally when setting up everything else.
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 
 	// Parse config, if specified, to fail early if it's invalid.
 	var conf *conffile.Config

cmd/tailscaled/tailscaled_windows.go

@@ -328,7 +328,7 @@ func beWindowsSubprocess() bool {
 		log.Printf("Error pre-loading \"%s\": %v", fqWintunPath, err)
 	}
 
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	netMon, err := netmon.New(log.Printf)
 	if err != nil {
 		log.Fatalf("Could not create netMon: %v", err)

cmd/tsconnect/wasm/wasm_js.go

@@ -100,7 +100,7 @@ func newIPN(jsConfig js.Value) map[string]any {
 	logtail := logtail.NewLogger(c, log.Printf)
 	logf := logtail.Logf
 
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	sys.Set(store)
 	dialer := &tsdial.Dialer{Logf: logf}
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{

ipn/ipnlocal/local_test.go

@@ -436,7 +436,7 @@ func (panicOnUseTransport) RoundTrip(*http.Request) (*http.Response, error) {
 }
 
 func newTestLocalBackend(t testing.TB) *LocalBackend {
-	return newTestLocalBackendWithSys(t, tsd.NewSystemWithEventBus())
+	return newTestLocalBackendWithSys(t, tsd.NewSystem())
 }
 
 // newTestLocalBackendWithSys creates a new LocalBackend with the given tsd.System.
@@ -4407,7 +4407,7 @@ func TestNotificationTargetMatch(t *testing.T) {
 type newTestControlFn func(tb testing.TB, opts controlclient.Options) controlclient.Client
 
 func newLocalBackendWithTestControl(t *testing.T, enableLogging bool, newControl newTestControlFn) *LocalBackend {
-	return newLocalBackendWithSysAndTestControl(t, enableLogging, new(tsd.System), newControl)
+	return newLocalBackendWithSysAndTestControl(t, enableLogging, tsd.NewSystem(), newControl)
 }
 
 func newLocalBackendWithSysAndTestControl(t *testing.T, enableLogging bool, sys *tsd.System, newControl newTestControlFn) *LocalBackend {
@@ -4867,7 +4867,7 @@ func TestConfigFileReload(t *testing.T) {
 			// Create backend with initial config
 			tc.initial.Path = path
 			tc.initial.Raw = initialJSON
-			sys := tsd.NewSystemWithEventBus()
+			sys := tsd.NewSystem()
 			sys.InitialConfig = tc.initial
 			b := newTestLocalBackendWithSys(t, sys)
 

ipn/ipnlocal/loglines_test.go

@@ -47,7 +47,7 @@ func TestLocalLogLines(t *testing.T) {
 	idA := logid(0xaa)
 
 	// set up a LocalBackend, super bare bones. No functional data.
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	store := new(mem.Store)
 	sys.Set(store)
 	e, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set, sys.HealthTracker(), sys.UserMetricsRegistry())

ipn/ipnlocal/serve_test.go

@@ -877,7 +877,7 @@ func newTestBackend(t *testing.T) *LocalBackend {
 		logf = logger.WithPrefix(tstest.WhileTestRunningLogger(t), "... ")
 	}
 
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	e, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
 		SetSubsystem:  sys.Set,
 		HealthTracker: sys.HealthTracker(),

ipn/ipnlocal/state_test.go

@@ -323,7 +323,7 @@ func TestStateMachine(t *testing.T) {
 	c := qt.New(t)
 
 	logf := tstest.WhileTestRunningLogger(t)
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	store := new(testStateStorage)
 	sys.Set(store)
 	e, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set, sys.HealthTracker(), sys.UserMetricsRegistry())
@@ -962,7 +962,7 @@ func TestStateMachine(t *testing.T) {
 
 func TestEditPrefsHasNoKeys(t *testing.T) {
 	logf := tstest.WhileTestRunningLogger(t)
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	sys.Set(new(mem.Store))
 	e, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set, sys.HealthTracker(), sys.UserMetricsRegistry())
 	if err != nil {
@@ -1042,7 +1042,7 @@ func TestWGEngineStatusRace(t *testing.T) {
 	t.Skip("test fails")
 	c := qt.New(t)
 	logf := tstest.WhileTestRunningLogger(t)
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	sys.Set(new(mem.Store))
 
 	eng, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set)

ipn/ipnserver/server_test.go

@@ -517,7 +517,7 @@ type newControlClientFn func(tb testing.TB, opts controlclient.Options) controlc
 func newLocalBackendWithTestControl(tb testing.TB, newControl newControlClientFn, enableLogging bool) *ipnlocal.LocalBackend {
 	tb.Helper()
 
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	store := &mem.Store{}
 	sys.Set(store)
 

ipn/localapi/localapi_test.go

@@ -336,7 +336,7 @@ func TestServeWatchIPNBus(t *testing.T) {
 
 func newTestLocalBackend(t testing.TB) *ipnlocal.LocalBackend {
 	var logf logger.Logf = logger.Discard
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	store := new(mem.Store)
 	sys.Set(store)
 	eng, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set, sys.HealthTracker(), sys.UserMetricsRegistry())

ssh/tailssh/tailssh_test.go

@@ -1037,7 +1037,7 @@ func TestSSHAuthFlow(t *testing.T) {
 
 func TestSSH(t *testing.T) {
 	var logf logger.Logf = t.Logf
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	eng, err := wgengine.NewFakeUserspaceEngine(logf, sys.Set, sys.HealthTracker(), sys.UserMetricsRegistry())
 	if err != nil {
 		t.Fatal(err)

tsd/tsd.go

@@ -40,6 +40,10 @@ import (
 )
 
 // System contains all the subsystems of a Tailscale node (tailscaled, etc.)
+//
+// A valid System value must always have a non-nil Bus populated.  Callers must
+// ensure this before using the value further. Call [NewSystem] to obtain a
+// value ready to use.
 type System struct {
 	Bus            SubSystem[*eventbus.Bus]
 	Dialer         SubSystem[*tsdial.Dialer]
@@ -72,9 +76,9 @@ type System struct {
 	userMetricsRegistry usermetric.Registry
 }
 
-// NewSystemWithEventBus constructs a new otherwise-empty system with a
+// NewSystem constructs a new otherwise-empty [System] with a
 // freshly-constructed event bus populated.
-func NewSystemWithEventBus() *System {
+func NewSystem() *System {
 	sys := new(System)
 	sys.Set(eventbus.New())
 	return sys

tsnet/tsnet.go

@@ -561,7 +561,7 @@ func (s *Server) start() (reterr error) {
 		s.Logf(format, a...)
 	}
 
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	s.sys = sys
 	if err := s.startLogger(&closePool, sys.HealthTracker(), tsLogf); err != nil {
 		return err

wgengine/bench/wg.go

@@ -46,7 +46,7 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netip.
 		logf: logger.WithPrefix(logf, "tun1: "),
 		traf: traf,
 	}
-	s1 := tsd.NewSystemWithEventBus()
+	s1 := tsd.NewSystem()
 	e1, err := wgengine.NewUserspaceEngine(l1, wgengine.Config{
 		Router:        router.NewFake(l1),
 		NetMon:        nil,
@@ -73,7 +73,7 @@ func setupWGTest(b *testing.B, logf logger.Logf, traf *TrafficGen, a1, a2 netip.
 		logf: logger.WithPrefix(logf, "tun2: "),
 		traf: traf,
 	}
-	s2 := tsd.NewSystemWithEventBus()
+	s2 := tsd.NewSystem()
 	e2, err := wgengine.NewUserspaceEngine(l2, wgengine.Config{
 		Router:        router.NewFake(l2),
 		NetMon:        nil,

wgengine/netstack/netstack_test.go

@@ -45,7 +45,7 @@ func TestInjectInboundLeak(t *testing.T) {
 			t.Logf(format, args...)
 		}
 	}
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
 		Tun:           tunDev,
 		Dialer:        dialer,
@@ -101,7 +101,7 @@ func getMemStats() (ms runtime.MemStats) {
 
 func makeNetstack(tb testing.TB, config func(*Impl)) *Impl {
 	tunDev := tstun.NewFake()
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	sys.Set(new(mem.Store))
 	dialer := new(tsdial.Dialer)
 	logf := tstest.WhileTestRunningLogger(tb)

wgengine/userspace_ext_test.go

@@ -16,7 +16,7 @@ import (
 )
 
 func TestIsNetstack(t *testing.T) {
-	sys := tsd.NewSystemWithEventBus()
+	sys := tsd.NewSystem()
 	e, err := wgengine.NewUserspaceEngine(
 		tstest.WhileTestRunningLogger(t),
 		wgengine.Config{
@@ -66,7 +66,7 @@ func TestIsNetstackRouter(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			sys := tsd.NewSystemWithEventBus()
+			sys := tsd.NewSystem()
 			if tt.setNetstackRouter {
 				sys.NetstackRouter.Set(true)
 			}