feat: make EvaluationReason use enums for Kind and ErrorKind

apps/hello-cpp/main.cpp

@@ -62,7 +62,9 @@ int main() {
 
     auto value = client.BoolVariationDetail("my-bool-flag", false);
     LD_LOG(logger, LogLevel::kInfo) << "Value was: " << *value;
-    LD_LOG(logger, LogLevel::kInfo) << "Reason was: " << value.Reason();
+    if (auto reason = value.Reason()) {
+        LD_LOG(logger, LogLevel::kInfo) << "Reason was: " << *reason;
+    }
 
     // Sit around.
     std::cout << "Press enter to exit" << std::endl;

libs/client-sdk/src/api.cpp

@@ -135,7 +135,8 @@ EvaluationDetail<T> Client::VariationInternal(FlagKey const& key,
                    "Returning default value";
 
             // TODO: SC-199918
-            auto error_reason = EvaluationReason("CLIENT_NOT_READY");
+            auto error_reason =
+                EvaluationReason(EvaluationReason::ErrorKind::kClientNotReady);
             if (eval_reasons_available_) {
                 event.reason = error_reason;
             }
@@ -147,7 +148,8 @@ EvaluationDetail<T> Client::VariationInternal(FlagKey const& key,
         LD_LOG(logger_, LogLevel::kInfo)
             << "Unknown feature flag " << key << "; returning default value";
 
-        auto error_reason = EvaluationReason("FLAG_NOT_FOUND");
+        auto error_reason =
+            EvaluationReason(EvaluationReason::ErrorKind::kFlagNotFound);
         if (eval_reasons_available_) {
             event.reason = error_reason;
         }
@@ -168,7 +170,8 @@ EvaluationDetail<T> Client::VariationInternal(FlagKey const& key,
 
     if (check_type && default_value.type() != Value::Type::kNull &&
         detail.value().type() != default_value.type()) {
-        auto error_reason = EvaluationReason("WRONG_TYPE");
+        auto error_reason =
+            EvaluationReason(EvaluationReason::ErrorKind::kWrongType);
         if (eval_reasons_available_) {
             event.reason = error_reason;
         }
@@ -191,14 +194,8 @@ EvaluationDetail<T> Client::VariationInternal(FlagKey const& key,
 
     event_processor_->AsyncSend(std::move(event));
 
-    // TODO: this isn't a valid error, figure out how to handle if reason is
-    // missing.
-    EvaluationReason returned_reason("UNKNOWN");
-    if (detail.reason()) {
-        returned_reason = detail.reason()->get();
-    }
     return EvaluationDetail<T>(detail.value(), detail.variation_index(),
-                               returned_reason);
+                               detail.reason());
 }
 
 EvaluationDetail<bool> Client::BoolVariationDetail(Client::FlagKey const& key,

libs/common/include/data/evaluation_detail.hpp

@@ -25,15 +25,15 @@ class EvaluationDetail {
      */
     EvaluationDetail(T value,
                      std::optional<std::size_t> variation_index,
-                     EvaluationReason reason);
+                     std::optional<EvaluationReason> reason);
 
     /**
      * Constructs an EvaluationDetail representing an error and a default
      * value.
      * @param error_kind Kind of the error.
      * @param default_value Default value.
      */
-    EvaluationDetail(std::string error_kind, T default_value);
+    EvaluationDetail(EvaluationReason::ErrorKind error_kind, T default_value);
 
     /**
      * @return A reference to the variation value. For convenience, the *
@@ -50,7 +50,7 @@ class EvaluationDetail {
     /**
      * @return A reference to the reason for the results.
      */
-    [[nodiscard]] EvaluationReason const& Reason() const;
+    [[nodiscard]] std::optional<EvaluationReason> const& Reason() const;
 
     /**
      * @return A reference to the variation value.
@@ -60,6 +60,6 @@ class EvaluationDetail {
    private:
     T value_;
     std::optional<std::size_t> variation_index_;
-    EvaluationReason reason_;
+    std::optional<EvaluationReason> reason_;
 };
 }  // namespace launchdarkly

libs/common/include/data/evaluation_reason.hpp

@@ -12,28 +12,53 @@ namespace launchdarkly {
  */
 class EvaluationReason {
    public:
+    enum class Kind {
+        // The flag was off and therefore returned its configured off value.
+        kOff = 0,
+        // The flag was on but the context did not match any targets or rules.
+        kFallthrough = 1,
+        // The context key was specifically targeted for this flag.
+        kTargetMatch = 2,
+        // The context matched one of the flag's rules.
+        kRuleMatch = 3,
+        // The flag was considered off because it had at least one prerequisite
+        // flag that either was off or did not return the desired variation.
+        kPrerequisiteFailed = 4,
+        // The flag could not be evaluated, e.g. because it does not exist or
+        // due to an unexpected error.
+        kError = 5
+    };
+    friend std::ostream& operator<<(std::ostream& out, Kind const& kind);
+
+    enum class ErrorKind {
+        // The SDK was not yet fully initialized and cannot evaluate flags.
+        kClientNotReady = 0,
+        // The application did not pass valid context attributes to the SDK
+        // evaluation method.
+        kUserNotSpecified = 1,
+        // No flag existed with the specified flag key.
+        kFlagNotFound = 2,
+        // The application requested an evaluation result of one type but the
+        // resulting flag variation value was of a different type.
+        kWrongType = 3,
+        // The flag had invalid properties.
+        kMalformedFlag = 4,
+        // An unexpected error happened that stopped evaluation.
+        kException = 5,
+    };
+
+    friend std::ostream& operator<<(std::ostream& out, ErrorKind const& kind);
+
     /**
-     * The general category of the reason:
-     *
-     * - `"OFF"`: The flag was off and therefore returned its configured off
-     * value.
-     * - `"FALLTHROUGH"`: The flag was on but the context did not match any
-     * targets or rules.
-     * - `"TARGET_MATCH"`: The context key was specifically targeted for this
-     * flag.
-     * - `"RULE_MATCH"`: the context matched one of the flag"s rules.
-     * - `"PREREQUISITE_FAILED"`: The flag was considered off because it had at
-     * least one prerequisite flag that either was off or did not return the
-     * desired variation.
-     * - `"ERROR"`: The flag could not be evaluated, e.g. because it does not
-     * exist or due to an unexpected error.
+     * @return The general category of the reason.
      */
-    [[nodiscard]] std::string const& kind() const;
+    [[nodiscard]] Kind const& kind() const;
 
     /**
-     * A further description of the error condition, if the kind was `"ERROR"`.
+     * A further description of the error condition, if the Kind was
+     * Kind::kError.
      */
-    [[nodiscard]] std::optional<std::string> error_kind() const;
+    [[nodiscard]] std::optional<ErrorKind> error_kind() const;
 
     /**
      * The index of the matched rule (0 for the first), if the kind was
@@ -78,22 +103,22 @@ class EvaluationReason {
      */
     [[nodiscard]] std::optional<std::string> big_segment_status() const;
 
-    EvaluationReason(std::string kind,
-                     std::optional<std::string> error_kind,
+    EvaluationReason(Kind kind,
+                     std::optional<ErrorKind> error_kind,
                      std::optional<std::size_t> rule_index,
                      std::optional<std::string> rule_id,
                      std::optional<std::string> prerequisite_key,
                      bool in_experiment,
                      std::optional<std::string> big_segment_status);
 
-    explicit EvaluationReason(std::string error_kind);
+    explicit EvaluationReason(ErrorKind error_kind);
 
     friend std::ostream& operator<<(std::ostream& out,
                                     EvaluationReason const& reason);
 
    private:
-    std::string kind_;
-    std::optional<std::string> error_kind_;
+    Kind kind_;
+    std::optional<ErrorKind> error_kind_;
     std::optional<std::size_t> rule_index_;
     std::optional<std::string> rule_id_;
     std::optional<std::string> prerequisite_key_;

libs/common/include/serialization/json_evaluation_reason.hpp

@@ -18,6 +18,24 @@ tl::expected<EvaluationReason, JsonError> tag_invoke(
         unused,
     boost::json::value const& json_value);
 
+tl::expected<EvaluationReason::Kind, JsonError> tag_invoke(
+    boost::json::value_to_tag<
+        tl::expected<EvaluationReason::Kind, JsonError>> const& unused,
+    boost::json::value const& json_value);
+
+tl::expected<EvaluationReason::ErrorKind, JsonError> tag_invoke(
+    boost::json::value_to_tag<
+        tl::expected<EvaluationReason::ErrorKind, JsonError>> const& unused,
+    boost::json::value const& json_value);
+
+void tag_invoke(boost::json::value_from_tag const& unused,
+                boost::json::value& json_value,
+                EvaluationReason::Kind const& kind);
+
+void tag_invoke(boost::json::value_from_tag const& unused,
+                boost::json::value& json_value,
+                EvaluationReason::ErrorKind const& kind);
+
 void tag_invoke(boost::json::value_from_tag const& unused,
                 boost::json::value& json_value,
                 EvaluationReason const& reason);

libs/common/src/data/evaluation_detail.cpp

@@ -8,13 +8,14 @@ template <typename T>
 EvaluationDetail<T>::EvaluationDetail(
     T value,
     std::optional<std::size_t> variation_index,
-    launchdarkly::EvaluationReason reason)
+    std::optional<launchdarkly::EvaluationReason> reason)
     : value_(std::move(value)),
       variation_index_(variation_index),
       reason_(std::move(reason)) {}
 
 template <typename T>
-EvaluationDetail<T>::EvaluationDetail(std::string error_kind, T default_value)
+EvaluationDetail<T>::EvaluationDetail(EvaluationReason::ErrorKind error_kind,
+                                      T default_value)
     : value_(std::move(default_value)),
       variation_index_(std::nullopt),
       reason_(error_kind) {}
@@ -25,7 +26,7 @@ T const& EvaluationDetail<T>::Value() const {
 }
 
 template <typename T>
-EvaluationReason const& EvaluationDetail<T>::Reason() const {
+std::optional<EvaluationReason> const& EvaluationDetail<T>::Reason() const {
     return reason_;
 }
 

libs/common/src/data/evaluation_reason.cpp

@@ -1,12 +1,13 @@
 #include "data/evaluation_reason.hpp"
-
+#include "serialization/json_evaluation_reason.hpp"
 namespace launchdarkly {
 
-std::string const& EvaluationReason::kind() const {
+EvaluationReason::Kind const& EvaluationReason::kind() const {
     return kind_;
 }
 
-std::optional<std::string> EvaluationReason::error_kind() const {
+std::optional<EvaluationReason::ErrorKind> EvaluationReason::error_kind()
+    const {
     return error_kind_;
 }
 
@@ -31,23 +32,23 @@ std::optional<std::string> EvaluationReason::big_segment_status() const {
 }
 
 EvaluationReason::EvaluationReason(
-    std::string kind,
-    std::optional<std::string> error_kind,
+    Kind kind,
+    std::optional<ErrorKind> error_kind,
     std::optional<std::size_t> rule_index,
     std::optional<std::string> rule_id,
     std::optional<std::string> prerequisite_key,
     bool in_experiment,
     std::optional<std::string> big_segment_status)
-    : kind_(std::move(kind)),
-      error_kind_(std::move(error_kind)),
+    : kind_(kind),
+      error_kind_(error_kind),
       rule_index_(rule_index),
       rule_id_(std::move(rule_id)),
       prerequisite_key_(std::move(prerequisite_key)),
       in_experiment_(in_experiment),
       big_segment_status_(std::move(big_segment_status)) {}
 
-EvaluationReason::EvaluationReason(std::string error_kind)
-    : EvaluationReason("ERROR",
+EvaluationReason::EvaluationReason(ErrorKind error_kind)
+    : EvaluationReason(Kind::kError,
                        error_kind,
                        std::nullopt,
                        std::nullopt,
@@ -90,4 +91,17 @@ bool operator==(EvaluationReason const& lhs, EvaluationReason const& rhs) {
 bool operator!=(EvaluationReason const& lhs, EvaluationReason const& rhs) {
     return !(lhs == rhs);
 }
+
+std::ostream& operator<<(std::ostream& out,
+                         EvaluationReason::Kind const& kind) {
+    out << boost::json::value_from(kind).as_string();
+    return out;
+}
+
+std::ostream& operator<<(std::ostream& out,
+                         EvaluationReason::ErrorKind const& kind) {
+    out << boost::json::value_from(kind).as_string();
+    return out;
+}
+
 }  // namespace launchdarkly