tidy: Replace x.size() == 0 with x.empty() (envoyproxy#6511)

Signed-off-by: James Synge <jamessynge@google.com>

.clang-tidy

@@ -1,7 +1,7 @@
-Checks:          'clang-diagnostic-*,clang-analyzer-*,abseil-*,bugprone-*,modernize-*,performance-*,readability-redundant-*,readability-braces-around-statements'
+Checks:          'clang-diagnostic-*,clang-analyzer-*,abseil-*,bugprone-*,modernize-*,performance-*,readability-redundant-*,readability-braces-around-statements,readability-container-size-empty'
 
 #TODO(lizan): grow this list, fix possible warnings and make more checks as error
-WarningsAsErrors: 'bugprone-assert-side-effect,modernize-make-shared,modernize-make-unique,readability-redundant-smartptr-get,readability-braces-around-statements,readability-redundant-string-cstr,bugprone-use-after-move'
+WarningsAsErrors: 'bugprone-assert-side-effect,modernize-make-shared,modernize-make-unique,readability-redundant-smartptr-get,readability-braces-around-statements,readability-redundant-string-cstr,bugprone-use-after-move,readability-container-size-empty'
 
 CheckOptions:
   - key:             bugprone-assert-side-effect.AssertMacros

source/common/buffer/buffer_impl.cc

@@ -69,7 +69,7 @@ void OwnedImpl::prepend(absl::string_view data) {
     // only seems to happen the original buffer was created via
     // addBufferFragment(), this forces the code execution path in
     // evbuffer_prepend related to immutable buffers.
-    if (data.size() == 0) {
+    if (data.empty()) {
       return;
     }
     evbuffer_prepend(buffer_.get(), data.data(), data.size());

source/common/common/hex.cc

@@ -27,7 +27,7 @@ std::string Hex::encode(const uint8_t* data, size_t length) {
 }
 
 std::vector<uint8_t> Hex::decode(const std::string& hex_string) {
-  if (hex_string.size() == 0 || hex_string.size() % 2 != 0) {
+  if (hex_string.empty() || hex_string.size() % 2 != 0) {
     return {};
   }
 

source/common/config/grpc_mux_impl.cc

@@ -175,7 +175,7 @@ void GrpcMuxImpl::onDiscoveryResponse(
       }
       // onConfigUpdate should be called only on watches(clusters/routes) that have
       // updates in the message for EDS/RDS.
-      if (found_resources.size() > 0) {
+      if (!found_resources.empty()) {
         watch->callbacks_.onConfigUpdate(found_resources, message->version_info());
       }
     }

source/common/http/http1/conn_pool.cc

@@ -107,7 +107,7 @@ ConnectionPool::Cancellable* ConnPoolImpl::newStream(StreamDecoder& response_dec
     }
 
     // If we have no connections at all, make one no matter what so we don't starve.
-    if ((ready_clients_.size() == 0 && busy_clients_.size() == 0) || can_create_connection) {
+    if ((ready_clients_.empty() && busy_clients_.empty()) || can_create_connection) {
       createNewConnection();
     }
 

source/common/router/config_impl.cc

@@ -970,11 +970,11 @@ RouteMatcher::RouteMatcher(const envoy::api::v2::RouteConfiguration& route_confi
           throw EnvoyException(fmt::format("Only a single wildcard domain is permitted"));
         }
         default_virtual_host_ = virtual_host;
-      } else if (domain.size() > 0 && '*' == domain[0]) {
+      } else if (!domain.empty() && '*' == domain[0]) {
         duplicate_found = !wildcard_virtual_host_suffixes_[domain.size() - 1]
                                .emplace(domain.substr(1), virtual_host)
                                .second;
-      } else if (domain.size() > 0 && '*' == domain[domain.size() - 1]) {
+      } else if (!domain.empty() && '*' == domain[domain.size() - 1]) {
         duplicate_found = !wildcard_virtual_host_prefixes_[domain.size() - 1]
                                .emplace(domain.substr(0, domain.size() - 1), virtual_host)
                                .second;
@@ -1076,7 +1076,7 @@ VirtualHostImpl::virtualClusterFromEntries(const Http::HeaderMap& headers) const
     }
   }
 
-  if (virtual_clusters_.size() > 0) {
+  if (!virtual_clusters_.empty()) {
     return &VIRTUAL_CLUSTER_CATCH_ALL;
   }
 

source/common/router/header_formatter.cc

@@ -136,7 +136,7 @@ parsePerRequestStateField(absl::string_view param_str) {
     throw EnvoyException(formatPerRequestStateParseException(param_str));
   }
   modified_param_str = modified_param_str.substr(1, modified_param_str.size() - 2); // trim parens
-  if (modified_param_str.size() == 0) {
+  if (modified_param_str.empty()) {
     throw EnvoyException(formatPerRequestStateParseException(param_str));
   }
 

source/common/router/header_parser.cc

@@ -209,7 +209,7 @@ parseInternal(const envoy::api::v2::core::HeaderValueOption& header_value_option
     formatters.emplace_back(new PlainHeaderFormatter(unescape(literal), append));
   }
 
-  ASSERT(formatters.size() > 0);
+  ASSERT(!formatters.empty());
 
   if (formatters.size() == 1) {
     return std::move(formatters[0]);

source/common/router/rds_impl.cc

@@ -234,7 +234,7 @@ RouteConfigProviderManagerImpl::dumpRouteConfigs() const {
     // of this code, locking the weak_ptr will not fail.
     auto subscription = element.second.lock();
     ASSERT(subscription);
-    ASSERT(subscription->route_config_providers_.size() > 0);
+    ASSERT(!subscription->route_config_providers_.empty());
 
     if (subscription->config_info_) {
       auto* dynamic_config = config_dump->mutable_dynamic_route_configs()->Add();

source/common/router/shadow_writer_impl.cc

@@ -24,7 +24,7 @@ void ShadowWriterImpl::shadow(const std::string& cluster, Http::MessagePtr&& req
   ASSERT(!request->headers().Host()->value().empty());
   // Switch authority to add a shadow postfix. This allows upstream logging to make more sense.
   auto parts = StringUtil::splitToken(request->headers().Host()->value().c_str(), ":");
-  ASSERT(parts.size() > 0 && parts.size() <= 2);
+  ASSERT(!parts.empty() && parts.size() <= 2);
   request->headers().Host()->value(
       parts.size() == 2 ? absl::StrJoin(parts, "-shadow:")
                         : absl::StrCat(request->headers().Host()->value().c_str(), "-shadow"));

source/common/upstream/health_checker_impl.cc

@@ -306,7 +306,7 @@ TcpHealthCheckMatcher::MatchSegments TcpHealthCheckMatcher::loadProtoBytes(
 
   for (const auto& entry : byte_array) {
     const auto decoded = Hex::decode(entry.text());
-    if (decoded.size() == 0) {
+    if (decoded.empty()) {
       throw EnvoyException(fmt::format("invalid hex string '{}'", entry.text()));
     }
     result.push_back(decoded);

source/common/upstream/load_balancer_impl.cc

@@ -136,7 +136,7 @@ void LoadBalancerBase::recalculatePerPriorityState(uint32_t priority,
   // by the overprovisioning factor.
   HostSet& host_set = *priority_set.hostSetsPerPriority()[priority];
   per_priority_health.get()[priority] = 0;
-  if (host_set.hosts().size() > 0) {
+  if (!host_set.hosts().empty()) {
     // Each priority level's health is ratio of healthy hosts to total number of hosts in a priority
     // multiplied by overprovisioning factor of 1.4 and capped at 100%. It means that if all
     // hosts are healthy that priority's health is 100%*1.4=140% and is capped at 100% which results
@@ -442,11 +442,11 @@ HostConstSharedPtr LoadBalancerBase::chooseHost(LoadBalancerContext* context) {
 bool LoadBalancerBase::isGlobalPanic(const HostSet& host_set) {
   uint64_t global_panic_threshold = std::min<uint64_t>(
       100, runtime_.snapshot().getInteger(RuntimePanicThreshold, default_healthy_panic_percent_));
-  double healthy_percent = host_set.hosts().size() == 0
+  double healthy_percent = host_set.hosts().empty()
                                ? 0
                                : 100.0 * host_set.healthyHosts().size() / host_set.hosts().size();
 
-  double degraded_percent = host_set.hosts().size() == 0
+  double degraded_percent = host_set.hosts().empty()
                                 ? 0
                                 : 100.0 * host_set.degradedHosts().size() / host_set.hosts().size();
   // If the % of healthy hosts in the cluster is less than our panic threshold, we use all hosts.
@@ -692,7 +692,7 @@ HostConstSharedPtr EdfLoadBalancerBase::chooseHostOnce(LoadBalancerContext* cont
     return host;
   } else {
     const HostVector& hosts_to_use = hostSourceToHosts(hosts_source);
-    if (hosts_to_use.size() == 0) {
+    if (hosts_to_use.empty()) {
       return nullptr;
     }
     return unweightedHostPick(hosts_to_use, hosts_source);

source/common/upstream/load_stats_reporter.cc

@@ -59,7 +59,7 @@ void LoadStatsReporter::sendLoadStatsRequest() {
     for (auto& host_set : cluster.prioritySet().hostSetsPerPriority()) {
       ENVOY_LOG(trace, "Load report locality count {}", host_set->hostsPerLocality().get().size());
       for (auto& hosts : host_set->hostsPerLocality().get()) {
-        ASSERT(hosts.size() > 0);
+        ASSERT(!hosts.empty());
         uint64_t rq_success = 0;
         uint64_t rq_error = 0;
         uint64_t rq_active = 0;

source/common/upstream/original_dst_cluster.cc

@@ -175,7 +175,7 @@ void OriginalDstCluster::cleanup() {
     }
   }
 
-  if (to_be_removed.size() > 0) {
+  if (!to_be_removed.empty()) {
     priority_set_.updateHosts(0,
                               HostSetImpl::partitionHosts(new_hosts, HostsPerLocalityImpl::empty()),
                               {}, {}, to_be_removed, absl::nullopt);

source/common/upstream/subset_lb.cc

@@ -318,7 +318,7 @@ bool SubsetLoadBalancer::hostMatches(const SubsetMetadata& kvs, const Host& host
       host_metadata.filter_metadata().find(Config::MetadataFilters::get().ENVOY_LB);
 
   if (filter_it == host_metadata.filter_metadata().end()) {
-    return kvs.size() == 0;
+    return kvs.empty();
   }
 
   const ProtobufWkt::Struct& data_struct = filter_it->second;

source/common/upstream/upstream_impl.cc

@@ -102,7 +102,7 @@ parseClusterSocketOptions(const envoy::api::v2::Cluster& config,
   // Cluster socket_options trump cluster manager wide.
   if (bind_config.socket_options().size() + config.upstream_bind_config().socket_options().size() >
       0) {
-    auto socket_options = config.upstream_bind_config().socket_options().size() > 0
+    auto socket_options = !config.upstream_bind_config().socket_options().empty()
                               ? config.upstream_bind_config().socket_options()
                               : bind_config.socket_options();
     Network::Socket::appendOptions(

source/extensions/filters/http/header_to_metadata/header_to_metadata_filter.cc

@@ -30,7 +30,7 @@ Config::Config(const envoy::config::filter::http::header_to_metadata::v2::Config
 
 bool Config::configToVector(const ProtobufRepeatedRule& proto_rules,
                             HeaderToMetadataRules& vector) {
-  if (proto_rules.size() == 0) {
+  if (proto_rules.empty()) {
     ENVOY_LOG(debug, "no rules provided");
     return false;
   }
@@ -174,7 +174,7 @@ void HeaderToMetadataFilter::writeHeaderToMetadata(Http::HeaderMap& headers,
   }
 
   // Any matching rules?
-  if (structs_by_namespace.size() > 0) {
+  if (!structs_by_namespace.empty()) {
     for (auto const& entry : structs_by_namespace) {
       callbacks.streamInfo().setDynamicMetadata(entry.first, entry.second);
     }

source/extensions/filters/http/jwt_authn/verifier.cc

@@ -54,7 +54,7 @@ class ContextImpl : public Verifier::Context {
   }
 
   void setPayload() {
-    if (payload_.fields().size() > 0) {
+    if (!payload_.fields().empty()) {
       callback_->setPayload(payload_);
     }
   }

source/extensions/filters/network/http_connection_manager/config.cc

@@ -284,7 +284,7 @@ HttpConnectionManagerConfig::HttpConnectionManagerConfig(
       throw EnvoyException(
           fmt::format("Error: multiple upgrade configs with the same name: '{}'", name));
     }
-    if (upgrade_config.filters().size() > 0) {
+    if (!upgrade_config.filters().empty()) {
       std::unique_ptr<FilterFactoriesList> factories = std::make_unique<FilterFactoriesList>();
       for (int32_t i = 0; i < upgrade_config.filters().size(); i++) {
         processFilter(upgrade_config.filters(i), i, name, *factories);

source/extensions/tracers/zipkin/span_context_extractor.cc

@@ -105,7 +105,7 @@ std::pair<SpanContext, bool> SpanContextExtractor::extractSpanContext(bool is_sa
     }
 
     auto b3_parent_id_entry = request_headers_.get(ZipkinCoreConstants::get().X_B3_PARENT_SPAN_ID);
-    if (b3_parent_id_entry && b3_parent_id_entry->value().size() > 0) {
+    if (b3_parent_id_entry && !b3_parent_id_entry->value().empty()) {
       const std::string pspid = b3_parent_id_entry->value().c_str();
       if (!StringUtil::atoull(pspid.c_str(), parent_id, 16)) {
         throw ExtractorException(fmt::format("Invalid parent span id {}", pspid.c_str()));

source/extensions/tracers/zipkin/util.cc

@@ -35,7 +35,7 @@ void Util::addArrayToJson(std::string& target, const std::vector<std::string>& j
                           const std::string& field_name) {
   std::string stringified_json_array = "[";
 
-  if (json_array.size() > 0) {
+  if (!json_array.empty()) {
     stringified_json_array += json_array[0];
     for (auto it = json_array.begin() + 1; it != json_array.end(); it++) {
       stringified_json_array += ",";

source/extensions/tracers/zipkin/zipkin_core_types.cc

@@ -253,7 +253,7 @@ void Span::finish() {
 }
 
 void Span::setTag(const std::string& name, const std::string& value) {
-  if (name.size() > 0 && value.size() > 0) {
+  if (!name.empty() && !value.empty()) {
     addBinaryAnnotation(BinaryAnnotation(name, value));
   }
 }

source/extensions/tracers/zipkin/zipkin_tracer_impl.cc

@@ -75,7 +75,7 @@ Driver::Driver(const envoy::config::trace::v2::ZipkinConfig& zipkin_config,
   cluster_ = cm_.get(zipkin_config.collector_cluster())->info();
 
   std::string collector_endpoint = ZipkinCoreConstants::get().DEFAULT_COLLECTOR_ENDPOINT;
-  if (zipkin_config.collector_endpoint().size() > 0) {
+  if (!zipkin_config.collector_endpoint().empty()) {
     collector_endpoint = zipkin_config.collector_endpoint();
   }
 

source/server/http/admin.cc

@@ -586,7 +586,7 @@ Http::Code AdminImpl::handlerLogging(absl::string_view url, Http::HeaderMap&,
   Http::Utility::QueryParams query_params = Http::Utility::parseQueryString(url);
 
   Http::Code rc = Http::Code::OK;
-  if (query_params.size() > 0 && !changeLogLevel(query_params)) {
+  if (!query_params.empty() && !changeLogLevel(query_params)) {
     response.add("usage: /logging?<name>=<level> (change single level)\n");
     response.add("usage: /logging?level=<level> (change all levels)\n");
     response.add("levels: ");

source/server/listener_manager_impl.cc

@@ -185,7 +185,7 @@ ListenerImpl::ListenerImpl(const envoy::api::v2::Listener& config, const std::st
         config.tcp_fast_open_queue_length().value()));
   }
 
-  if (config.socket_options().size() > 0) {
+  if (!config.socket_options().empty()) {
     addListenSocketOptions(
         Network::SocketOptionFactory::buildLiteralOptions(config.socket_options()));
   }

test/common/upstream/health_checker_impl_test.cc

@@ -2809,7 +2809,7 @@ class GrpcHealthCheckerImplTestBase {
   }
 
   void respondResponseSpec(size_t index, ResponseSpec&& spec) {
-    const bool trailers_empty = spec.trailers.size() == 0U;
+    const bool trailers_empty = spec.trailers.empty();
     const bool end_stream_on_headers = spec.body_chunks.empty() && trailers_empty;
     auto response_headers = std::make_unique<Http::TestHeaderMapImpl>();
     for (const auto& header : spec.response_headers) {

test/common/upstream/load_balancer_impl_test.cc

@@ -203,7 +203,7 @@ TEST_P(LoadBalancerBaseTest, PrioritySelectionFuzz) {
       // Either we selected one of the healthy hosts or we failed to select anything and defaulted
       // to healthy.
       EXPECT_TRUE(!hs.first.healthyHosts().empty() ||
-                  (hs.first.healthyHosts().size() == 0 && hs.first.degradedHosts().size() == 0));
+                  (hs.first.healthyHosts().empty() && hs.first.degradedHosts().empty()));
       break;
     case LoadBalancerBase::HostAvailability::Degraded:
       EXPECT_FALSE(hs.first.degradedHosts().empty());

test/extensions/filters/http/header_to_metadata/header_to_metadata_filter_test.cc

@@ -52,7 +52,7 @@ class HeaderToMetadataTest : public testing::Test {
 
 MATCHER_P(MapEq, rhs, "") {
   const ProtobufWkt::Struct& obj = arg;
-  EXPECT_TRUE(rhs.size() > 0);
+  EXPECT_TRUE(!rhs.empty());
   for (auto const& entry : rhs) {
     EXPECT_EQ(obj.fields().at(entry.first).string_value(), entry.second);
   }
@@ -61,7 +61,7 @@ MATCHER_P(MapEq, rhs, "") {
 
 MATCHER_P(MapEqNum, rhs, "") {
   const ProtobufWkt::Struct& obj = arg;
-  EXPECT_TRUE(rhs.size() > 0);
+  EXPECT_TRUE(!rhs.empty());
   for (auto const& entry : rhs) {
     EXPECT_EQ(obj.fields().at(entry.first).number_value(), entry.second);
   }

test/extensions/filters/network/thrift_proxy/integration.cc

@@ -67,7 +67,7 @@ void BaseThriftIntegrationTest::preparePayloads(const PayloadOptions& options,
     args.push_back(*options.service_name_);
   }
 
-  if (options.headers_.size() > 0) {
+  if (!options.headers_.empty()) {
     args.push_back("-H");
 
     std::vector<std::string> headers;

test/extensions/filters/network/zookeeper_proxy/zookeeper_filter_test.cc

@@ -16,7 +16,7 @@ namespace NetworkFilters {
 namespace ZooKeeperProxy {
 
 bool protoMapEq(const ProtobufWkt::Struct& obj, const std::map<std::string, std::string>& rhs) {
-  EXPECT_TRUE(rhs.size() > 0);
+  EXPECT_TRUE(!rhs.empty());
   for (auto const& entry : rhs) {
     EXPECT_EQ(obj.fields().at(entry.first).string_value(), entry.second);
   }

test/integration/h1_capture_direct_response_fuzz_test.cc

@@ -27,7 +27,7 @@ void H1FuzzIntegrationTest::initialize() {
 }
 
 DEFINE_PROTO_FUZZER(const test::integration::CaptureFuzzTestCase& input) {
-  RELEASE_ASSERT(TestEnvironment::getIpVersionsForTest().size() > 0, "");
+  RELEASE_ASSERT(!TestEnvironment::getIpVersionsForTest().empty(), "");
   const auto ip_version = TestEnvironment::getIpVersionsForTest()[0];
   H1FuzzIntegrationTest h1_fuzz_integration_test(ip_version);
   h1_fuzz_integration_test.replay(input);

test/integration/h1_capture_fuzz_test.cc

@@ -5,7 +5,7 @@ void H1FuzzIntegrationTest::initialize() { HttpIntegrationTest::initialize(); }
 
 DEFINE_PROTO_FUZZER(const test::integration::CaptureFuzzTestCase& input) {
   // Pick an IP version to use for loopback, it doesn't matter which.
-  RELEASE_ASSERT(TestEnvironment::getIpVersionsForTest().size() > 0, "");
+  RELEASE_ASSERT(!TestEnvironment::getIpVersionsForTest().empty(), "");
   const auto ip_version = TestEnvironment::getIpVersionsForTest()[0];
   H1FuzzIntegrationTest h1_fuzz_integration_test(ip_version);
   h1_fuzz_integration_test.replay(input);