use Abseil's optional in Bazel builds, for Envoy.

Author: dgoffredo

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",
@@ -74,6 +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",
@@ -111,5 +113,6 @@ cc_library(
     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
@@ -132,6 +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

src/datadog/collector.h

@@ -11,7 +11,7 @@
 // `response_handler` parameter to `Collector::send`.
 
 #include <memory>
-#include <optional>
+#include "optional.h"
 #include <vector>
 
 #include "expected.h"

src/datadog/curl.cpp

@@ -71,7 +71,7 @@ class CurlImpl {
    public:
     explicit HeaderReader(
         std::unordered_map<std::string, std::string> *response_headers_lower);
-    std::optional<StringView> lookup(StringView key) const override;
+    Optional<StringView> lookup(StringView key) const override;
     void visit(const std::function<void(StringView key, StringView value)>
                    &visitor) const override;
   };
@@ -438,7 +438,7 @@ CurlImpl::HeaderReader::HeaderReader(
     std::unordered_map<std::string, std::string> *response_headers_lower)
     : response_headers_lower_(response_headers_lower) {}
 
-std::optional<StringView> CurlImpl::HeaderReader::lookup(StringView key) const {
+Optional<StringView> CurlImpl::HeaderReader::lookup(StringView key) const {
   buffer_.clear();
   std::transform(key.begin(), key.end(), std::back_inserter(buffer_),
                  &to_lower);

src/datadog/dict_reader.h

@@ -5,7 +5,7 @@
 // context from externalized formats: HTTP headers, gRPC metadata, etc.
 
 #include <functional>
-#include <optional>
+#include "optional.h"
 
 #include "string_view.h"
 
@@ -18,7 +18,7 @@ class DictReader {
 
   // Return the value at the specified `key`, or return `std::nullopt` if there
   // is no value at `key`.
-  virtual std::optional<StringView> lookup(StringView 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(

src/datadog/environment.cpp

@@ -10,7 +10,7 @@ namespace environment {
 
 StringView name(Variable variable) { return variable_names[variable]; }
 
-std::optional<StringView> lookup(Variable variable) {
+Optional<StringView> lookup(Variable variable) {
   const char *name = variable_names[variable];
   const char *value = std::getenv(name);
   if (!value) {

src/datadog/environment.h

@@ -14,7 +14,7 @@
 //
 // `lookup` retrieves the value of `Variable` in the environment.
 
-#include <optional>
+#include "optional.h"
 
 #include "json_fwd.hpp"
 #include "string_view.h"
@@ -70,7 +70,7 @@ StringView name(Variable variable);
 
 // Return the value of the specified environment `variable`, or return
 // `std::nullptr` if that variable is not set in the environment.
-std::optional<StringView> lookup(Variable variable);
+Optional<StringView> lookup(Variable variable);
 
 nlohmann::json to_json();
 

src/datadog/expected.h

@@ -35,9 +35,9 @@
 //
 // `Expected<void>` is like `Expected<T>`, except that if the value is not an
 // error then it cannot be "dereferenced" with `operator*`, i.e. it is analogous
-// to `std::optional<Error>` (and is implemented as such).
+// to `Optional<Error>` (and is implemented as such).
 
-#include <optional>
+#include "optional.h"
 #include <variant>
 
 #include "error.h"
@@ -189,7 +189,7 @@ const Error* Expected<Value>::if_error() const& {
 
 template <>
 class Expected<void> {
-  std::optional<Error> data_;
+  Optional<Error> data_;
 
  public:
   Expected() = default;

src/datadog/http_client.h

@@ -10,7 +10,7 @@
 
 #include <chrono>
 #include <functional>
-#include <optional>
+#include "optional.h"
 
 #include "error.h"
 #include "expected.h"

src/datadog/net_util.cpp

@@ -9,7 +9,7 @@
 namespace datadog {
 namespace tracing {
 
-std::optional<std::string> get_hostname() {
+Optional<std::string> get_hostname() {
   char buffer[256];
   if (::gethostname(buffer, sizeof buffer)) {
     return std::nullopt;