Support conditional use of Abseil's string_view and optional, for Envoy.

BUILD.bazel

@@ -24,6 +24,7 @@ cc_library(
     "src/datadog/msgpack.cpp",
     "src/datadog/net_util.cpp",
     "src/datadog/null_collector.cpp",
+    "src/datadog/optional.cpp",
     "src/datadog/parse_util.cpp",
     "src/datadog/propagation_styles.cpp",
     "src/datadog/rate.cpp",
@@ -38,6 +39,7 @@ cc_library(
     "src/datadog/span_matcher.cpp",
     "src/datadog/span_sampler_config.cpp",
     "src/datadog/span_sampler.cpp",
+    "src/datadog/string_view.cpp",
     "src/datadog/tag_propagation.cpp",
     "src/datadog/tags.cpp",
     "src/datadog/threaded_event_scheduler.cpp",
@@ -73,6 +75,7 @@ cc_library(
     "src/datadog/msgpack.h",
     "src/datadog/net_util.h",
     "src/datadog/null_collector.h",
+    "src/datadog/optional.h",
     "src/datadog/parse_util.h",
     "src/datadog/propagation_styles.h",
     "src/datadog/rate.h",
@@ -87,6 +90,7 @@ cc_library(
     "src/datadog/span_matcher.h",
     "src/datadog/span_sampler_config.h",
     "src/datadog/span_sampler.h",
+    "src/datadog/string_view.h",
     "src/datadog/tag_propagation.h",
     "src/datadog/tags.h",
     "src/datadog/threaded_event_scheduler.h",
@@ -103,7 +107,12 @@ cc_library(
         "-Werror",
         "-pedantic",
         "-std=c++17",
+        "-DDD_USE_ABSEIL_FOR_ENVOY",
     ],
     strip_include_prefix = "src/",
     visibility = ["//visibility:public"],
+    deps = [
+        "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/types:optional",
+    ],
 )

CMakeLists.txt

@@ -76,6 +76,7 @@ target_sources(dd_trace_cpp PRIVATE
     src/datadog/msgpack.cpp
     src/datadog/net_util.cpp
     src/datadog/null_collector.cpp
+    src/datadog/optional.cpp
     src/datadog/parse_util.cpp
     src/datadog/propagation_styles.cpp
     src/datadog/rate.cpp
@@ -90,6 +91,7 @@ target_sources(dd_trace_cpp PRIVATE
     src/datadog/span_matcher.cpp
     src/datadog/span_sampler_config.cpp
     src/datadog/span_sampler.cpp
+    src/datadog/string_view.cpp
     src/datadog/tag_propagation.cpp
     src/datadog/tags.cpp
     src/datadog/threaded_event_scheduler.cpp
@@ -131,6 +133,7 @@ target_sources(dd_trace_cpp PUBLIC
   src/datadog/msgpack.h
   src/datadog/net_util.h
   src/datadog/null_collector.h
+  src/datadog/optional.h
   src/datadog/parse_util.h
   src/datadog/propagation_styles.h
   src/datadog/rate.h
@@ -145,6 +148,7 @@ target_sources(dd_trace_cpp PUBLIC
   src/datadog/span_matcher.h
   src/datadog/span_sampler_config.h
   src/datadog/span_sampler.h
+  src/datadog/string_view.h
   src/datadog/tag_propagation.h
   src/datadog/tags.h
   src/datadog/threaded_event_scheduler.h

WORKSPACE

@@ -0,0 +1,27 @@
+# The Bazel build is primarily for use by Envoy.
+#
+# Envoy forbids use of std::string_view and std::optional, preferring use of
+# Abseil's absl::string_view and absl::optional instead.
+#
+# In the context of an Envoy build, the Abseil libraries point to whatever
+# versions Envoy uses.
+#
+# To test this library's Bazel build independent of Envoy, we need to specify
+# versions of the Abseil libraries. That is what this file is for.
+
+# These rules are based on <https://abseil.io/docs/cpp/quickstart>,
+# accessed December 6, 2022.
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+  name = "com_google_absl",
+  urls = ["https://github.com/abseil/abseil-cpp/archive/98eb410c93ad059f9bba1bf43f5bb916fc92a5ea.zip"],
+  sha256 = "aabf6c57e3834f8dc3873a927f37eaf69975d4b28117fc7427dfb1c661542a87",
+  strip_prefix = "abseil-cpp-98eb410c93ad059f9bba1bf43f5bb916fc92a5ea",
+)
+
+http_archive(
+  name = "bazel_skylib",
+  urls = ["https://github.com/bazelbuild/bazel-skylib/releases/download/1.2.1/bazel-skylib-1.2.1.tar.gz"],
+  sha256 = "f7be3474d42aae265405a592bb7da8e171919d74c16f082a5457840f06054728",
+)

src/datadog/collector.h

@@ -11,11 +11,11 @@
 // `response_handler` parameter to `Collector::send`.
 
 #include <memory>
-#include <optional>
 #include <vector>
 
 #include "expected.h"
 #include "json_fwd.hpp"
+#include "optional.h"
 
 namespace datadog {
 namespace tracing {

src/datadog/collector_response.cpp

@@ -3,8 +3,7 @@
 namespace datadog {
 namespace tracing {
 
-std::string CollectorResponse::key(std::string_view service,
-                                   std::string_view environment) {
+std::string CollectorResponse::key(StringView service, StringView environment) {
   std::string result;
   result += "service:";
   result += service;

src/datadog/collector_response.h

@@ -14,17 +14,16 @@
 // information.
 
 #include <string>
-#include <string_view>
 #include <unordered_map>
 
 #include "rate.h"
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
 
 struct CollectorResponse {
-  static std::string key(std::string_view service,
-                         std::string_view environment);
+  static std::string key(StringView service, StringView environment);
   static const std::string key_of_default_rate;
   std::unordered_map<std::string, Rate> sample_rate_by_key;
 };

src/datadog/curl.cpp

@@ -11,7 +11,6 @@
 #include <list>
 #include <memory>
 #include <mutex>
-#include <string_view>
 #include <thread>
 #include <unordered_map>
 #include <unordered_set>
@@ -22,6 +21,7 @@
 #include "json.hpp"
 #include "logger.h"
 #include "parse_util.h"
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -61,7 +61,7 @@ class CurlImpl {
    public:
     ~HeaderWriter();
     curl_slist *release();
-    void set(std::string_view key, std::string_view value) override;
+    void set(StringView key, StringView value) override;
   };
 
   class HeaderReader : public DictReader {
@@ -71,10 +71,9 @@ class CurlImpl {
    public:
     explicit HeaderReader(
         std::unordered_map<std::string, std::string> *response_headers_lower);
-    std::optional<std::string_view> lookup(std::string_view key) const override;
-    void visit(
-        const std::function<void(std::string_view key, std::string_view value)>
-            &visitor) const override;
+    Optional<StringView> lookup(StringView key) const override;
+    void visit(const std::function<void(StringView key, StringView value)>
+                   &visitor) const override;
   };
 
   void run();
@@ -88,7 +87,7 @@ class CurlImpl {
                                   void *user_data);
   static bool is_non_whitespace(unsigned char);
   static char to_lower(unsigned char);
-  static std::string_view trim(std::string_view);
+  static StringView trim(StringView);
 
  public:
   explicit CurlImpl(const std::shared_ptr<Logger> &logger);
@@ -426,7 +425,7 @@ curl_slist *CurlImpl::HeaderWriter::release() {
   return list;
 }
 
-void CurlImpl::HeaderWriter::set(std::string_view key, std::string_view value) {
+void CurlImpl::HeaderWriter::set(StringView key, StringView value) {
   buffer_.clear();
   buffer_ += key;
   buffer_ += ": ";
@@ -439,8 +438,7 @@ CurlImpl::HeaderReader::HeaderReader(
     std::unordered_map<std::string, std::string> *response_headers_lower)
     : response_headers_lower_(response_headers_lower) {}
 
-std::optional<std::string_view> CurlImpl::HeaderReader::lookup(
-    std::string_view key) const {
+Optional<StringView> CurlImpl::HeaderReader::lookup(StringView key) const {
   buffer_.clear();
   std::transform(key.begin(), key.end(), std::back_inserter(buffer_),
                  &to_lower);
@@ -453,8 +451,8 @@ std::optional<std::string_view> CurlImpl::HeaderReader::lookup(
 }
 
 void CurlImpl::HeaderReader::visit(
-    const std::function<void(std::string_view key, std::string_view value)>
-        &visitor) const {
+    const std::function<void(StringView key, StringView value)> &visitor)
+    const {
   for (const auto &[key, value] : *response_headers_lower_) {
     visitor(key, value);
   }

src/datadog/datadog_agent.cpp

@@ -21,7 +21,7 @@ namespace datadog {
 namespace tracing {
 namespace {
 
-const std::string_view traces_api_path = "/v0.4/traces";
+const StringView traces_api_path = "/v0.4/traces";
 
 HTTPClient::URL traces_endpoint(const HTTPClient::URL& agent_url) {
   auto traces_url = agent_url;
@@ -49,10 +49,10 @@ Expected<void> msgpack_encode(
 }
 
 std::variant<CollectorResponse, std::string> parse_agent_traces_response(
-    std::string_view body) try {
+    StringView body) try {
   nlohmann::json response = nlohmann::json::parse(body);
 
-  std::string_view type = response.type_name();
+  StringView type = response.type_name();
   if (type != "object") {
     std::string message;
     message +=
@@ -66,7 +66,7 @@ std::variant<CollectorResponse, std::string> parse_agent_traces_response(
     return message;
   }
 
-  const std::string_view sample_rates_property = "rate_by_service";
+  const StringView sample_rates_property = "rate_by_service";
   const auto found = response.find(sample_rates_property);
   if (found == response.end()) {
     return CollectorResponse{};

src/datadog/datadog_agent_config.cpp

@@ -11,8 +11,8 @@
 namespace datadog {
 namespace tracing {
 
-Expected<HTTPClient::URL> DatadogAgentConfig::parse(std::string_view input) {
-  const std::string_view separator = "://";
+Expected<HTTPClient::URL> DatadogAgentConfig::parse(StringView input) {
+  const StringView separator = "://";
   const auto after_scheme = std::search(input.begin(), input.end(),
                                         separator.begin(), separator.end());
   if (after_scheme == input.end()) {
@@ -23,9 +23,9 @@ Expected<HTTPClient::URL> DatadogAgentConfig::parse(std::string_view input) {
     return Error{Error::URL_MISSING_SEPARATOR, std::move(message)};
   }
 
-  const std::string_view scheme = range(input.begin(), after_scheme);
-  const std::string_view supported[] = {"http", "https", "unix", "http+unix",
-                                        "https+unix"};
+  const StringView scheme = range(input.begin(), after_scheme);
+  const StringView supported[] = {"http", "https", "unix", "http+unix",
+                                  "https+unix"};
   const auto found =
       std::find(std::begin(supported), std::end(supported), scheme);
   if (found == std::end(supported)) {
@@ -42,7 +42,7 @@ Expected<HTTPClient::URL> DatadogAgentConfig::parse(std::string_view input) {
     return Error{Error::URL_UNSUPPORTED_SCHEME, std::move(message)};
   }
 
-  const std::string_view authority_and_path =
+  const StringView authority_and_path =
       range(after_scheme + separator.size(), input.end());
   // If the scheme is for unix domain sockets, then there's no way to
   // distinguish the path-to-socket from the path-to-resource.  Some

src/datadog/datadog_agent_config.h

@@ -14,11 +14,11 @@
 #include <chrono>
 #include <memory>
 #include <string>
-#include <string_view>
 #include <variant>
 
 #include "expected.h"
 #include "http_client.h"
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -50,7 +50,7 @@ struct DatadogAgentConfig {
   // How often, in milliseconds, to send batches of traces to the Datadog Agent.
   int flush_interval_milliseconds = 2000;
 
-  static Expected<HTTPClient::URL> parse(std::string_view);
+  static Expected<HTTPClient::URL> parse(StringView);
 };
 
 class FinalizedDatadogAgentConfig {

src/datadog/dict_reader.h

@@ -5,8 +5,9 @@
 // context from externalized formats: HTTP headers, gRPC metadata, etc.
 
 #include <functional>
-#include <optional>
-#include <string_view>
+
+#include "optional.h"
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -17,13 +18,12 @@ class DictReader {
 
   // Return the value at the specified `key`, or return `std::nullopt` if there
   // is no value at `key`.
-  virtual std::optional<std::string_view> lookup(
-      std::string_view key) const = 0;
+  virtual Optional<StringView> lookup(StringView key) const = 0;
 
   // Invoke the specified `visitor` once for each key/value pair in this object.
   virtual void visit(
-      const std::function<void(std::string_view key, std::string_view value)>&
-          visitor) const = 0;
+      const std::function<void(StringView key, StringView value)>& visitor)
+      const = 0;
 };
 
 }  // namespace tracing

src/datadog/dict_writer.h

@@ -8,7 +8,7 @@
 // permitted to result from repeated invocations of `DictWriter::set` with the
 // same key.
 
-#include <string_view>
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -20,7 +20,7 @@ class DictWriter {
   // Associate the specified `value` with the specified `key`.  An
   // implementation may, but is not required to, overwrite any previous value at
   // `key`.
-  virtual void set(std::string_view key, std::string_view value) = 0;
+  virtual void set(StringView key, StringView value) = 0;
 };
 
 }  // namespace tracing

src/datadog/environment.cpp

@@ -8,15 +8,15 @@ namespace datadog {
 namespace tracing {
 namespace environment {
 
-std::string_view name(Variable variable) { return variable_names[variable]; }
+StringView name(Variable variable) { return variable_names[variable]; }
 
-std::optional<std::string_view> lookup(Variable variable) {
+Optional<StringView> lookup(Variable variable) {
   const char *name = variable_names[variable];
   const char *value = std::getenv(name);
   if (!value) {
     return std::nullopt;
   }
-  return std::string_view{value};
+  return StringView{value};
 }
 
 nlohmann::json to_json() {