server,settings: assert tenant cluster version is initialized

It is invalid to start a tenant server if the version cluster setting
is not initialized. However, it's fairly easy for test code to forget
to do this, usually by mistakenly using
`cluster.MakeClusterSettings()` without calling
`clusterversion.Initialize()`.

This change adds an assertion that errors out if the version setting
is not set correctly.

Release note: None

pkg/clusterversion/clusterversion.go

@@ -59,6 +59,13 @@ func Initialize(ctx context.Context, ver roachpb.Version, sv *settings.Values) e
 	return version.initialize(ctx, ver, sv)
 }
 
+// AssertInitialized checks whether Initialize() has been called yet. This
+// is used in test code to assert that an initial cluster version has
+// been set when that matters.
+func AssertInitialized(ctx context.Context, sv *settings.Values) {
+	_ = version.activeVersion(ctx, sv)
+}
+
 // Handle is the interface through which callers access the active cluster
 // version and this binary's version details.
 type Handle interface {

pkg/server/testserver.go

@@ -1026,6 +1026,18 @@ func (ts *TestServer) StartTenant(
 	if st == nil {
 		st = cluster.MakeTestingClusterSettings()
 	}
+	// Verify that the settings object that was passed in has
+	// initialized the version setting. This is pretty much necessary
+	// for secondary tenants. See the comments at the beginning of
+	// `runStartSQL()` in cli/mt_start_sql.go and
+	// `makeSharedProcessTenantServerConfig()` in
+	// server_controller_new_server.go.
+	//
+	// The version is initialized in MakeTestingClusterSettings(). This
+	// assertion is there to prevent inadvertent changes to
+	// MakeTestingClusterSettings() and as a guardrail for tests that
+	// pass a custom params.Settings.
+	clusterversion.AssertInitialized(ctx, &st.SV)
 
 	// Needed for backward-compat on crdb_internal.ranges{_no_leases}.
 	// Remove in v23.2.

pkg/settings/cluster/cluster_settings.go

@@ -144,7 +144,9 @@ func MakeClusterSettings() *Settings {
 // object is needed, but cluster settings don't play a crucial role.
 func MakeTestingClusterSettings() *Settings {
 	return MakeTestingClusterSettingsWithVersions(
-		clusterversion.TestingBinaryVersion, clusterversion.TestingBinaryVersion, true /* initializeVersion */)
+		clusterversion.TestingBinaryVersion,
+		clusterversion.TestingBinaryVersion,
+		true /* initializeVersion */)
 }
 
 // MakeTestingClusterSettingsWithVersions returns a Settings object that has its