feat: add LDValue_SerializeJSON C binding (#458)

This adds a new API to the `LDValue` interface for serializing to a JSON
string.

Example:

```c
LDValue foo = LDValue_NewBool(true);
char *json = LDValue_SerializeJSON(foo);
// json is the string 'true'
LDMemory_FreeString(json);
LDValue_Free(foo);
```

It's easier to view this PR commit to commit. The first one was
necessary in order to access the boost::json tag_invoke implementations
in `common`, where `LDValue` is implemented. Luckily, I only needed to
pull over the `value` headers and some utilities.

One thing to note is that boost serializes numbers using scientific
notation (e.g. `17` serializes to `1.7E1`). Kind of an odd choice, but
it is to JSON spec.

BEGIN_COMMIT_OVERRIDE
refactor: move json_errors, primitives, and value from internal to common lib
feat: add LDValue_SerializeJSON C binding
END_COMMIT_OVERRIDE

Author: cwaldren-ld

contract-tests/client-contract-tests/src/client_entity.cpp

@@ -6,8 +6,8 @@
 #include <launchdarkly/context_builder.hpp>
 #include <launchdarkly/serialization/json_context.hpp>
 #include <launchdarkly/serialization/json_evaluation_reason.hpp>
-#include <launchdarkly/serialization/json_primitives.hpp>
-#include <launchdarkly/serialization/json_value.hpp>
+#include <launchdarkly/detail/serialization/json_primitives.hpp>
+#include <launchdarkly/detail/serialization/json_value.hpp>
 #include <launchdarkly/value.hpp>
 
 #include <chrono>

contract-tests/server-contract-tests/src/client_entity.cpp

@@ -6,8 +6,8 @@
 #include <launchdarkly/context_builder.hpp>
 #include <launchdarkly/serialization/json_context.hpp>
 #include <launchdarkly/serialization/json_evaluation_reason.hpp>
-#include <launchdarkly/serialization/json_primitives.hpp>
-#include <launchdarkly/serialization/json_value.hpp>
+#include <launchdarkly/detail/serialization/json_primitives.hpp>
+#include <launchdarkly/detail/serialization/json_value.hpp>
 #include <launchdarkly/server_side/serialization/json_all_flags_state.hpp>
 #include <launchdarkly/value.hpp>
 

libs/client-sdk/src/data_sources/data_source_event_handler.cpp

@@ -3,7 +3,7 @@
 #include <launchdarkly/encoding/base_64.hpp>
 #include <launchdarkly/serialization/json_evaluation_result.hpp>
 #include <launchdarkly/serialization/json_item_descriptor.hpp>
-#include <launchdarkly/serialization/json_primitives.hpp>
+#include <launchdarkly/detail/serialization/json_primitives.hpp>
 #include <launchdarkly/serialization/value_mapping.hpp>
 
 #include <boost/core/ignore_unused.hpp>

libs/client-sdk/src/flag_manager/flag_persistence.cpp

@@ -5,7 +5,7 @@
 
 #include <launchdarkly/serialization/json_evaluation_result.hpp>
 #include <launchdarkly/serialization/json_item_descriptor.hpp>
-#include <launchdarkly/serialization/json_primitives.hpp>
+#include <launchdarkly/detail/serialization/json_primitives.hpp>
 
 #include <utility>
 

libs/common/include/launchdarkly/bindings/c/value.h

@@ -191,6 +191,21 @@ LDValue_GetString(LDValue val);
 LD_EXPORT(unsigned int)
 LDValue_Count(LDValue val);
 
+/**
+ * Serializes the LDValue to a JSON value. The returning string should be
+ * freed with @ref LDMemory_FreeString.
+ *
+ * Please note that numbers are serialized using scientific notation;
+ * for example the number 17 would be serialized as '1.7E1'.
+ *
+ * @param val Target LDValue. Must not be NULL.
+ * @return A string containing the JSON representation of the LDValue. The
+ * string should be freed with @ref LDMemory_FreeString.
+ *
+ */
+LD_EXPORT(char*)
+LDValue_SerializeJSON(LDValue val);
+
 /**
  * Obtain iterator over an array-type @ref LDValue, otherwise NULL.
  *

libs/internal/include/launchdarkly/serialization/json_errors.hpp renamed to libs/common/include/launchdarkly/detail/serialization/json_errors.hpp

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <launchdarkly/serialization/json_errors.hpp>
+#include <launchdarkly/detail/serialization/json_errors.hpp>
 #include <tl/expected.hpp>
 
 #include <boost/core/ignore_unused.hpp>

libs/internal/include/launchdarkly/serialization/json_primitives.hpp renamed to libs/common/include/launchdarkly/detail/serialization/json_primitives.hpp

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <launchdarkly/serialization/json_errors.hpp>
+#include <launchdarkly/detail/serialization/json_errors.hpp>
 #include <launchdarkly/value.hpp>
 
 #include <boost/json/fwd.hpp>

libs/internal/include/launchdarkly/serialization/json_value.hpp renamed to libs/common/include/launchdarkly/detail/serialization/json_value.hpp

@@ -14,6 +14,7 @@ file(GLOB HEADER_LIST CONFIGURE_DEPENDS
         "${LaunchDarklyCommonSdk_SOURCE_DIR}/include/launchdarkly/data/*.hpp"
         "${LaunchDarklyCommonSdk_SOURCE_DIR}/include/launchdarkly/logging/*.hpp"
         "${LaunchDarklyCommonSdk_SOURCE_DIR}/include/launchdarkly/data_sources/*.hpp"
+        "${LaunchDarklyCommonSdk_SOURCE_DIR}/include/launchdarkly/data_sources/persistence/*.hpp"
 )
 
 # Automatic library: static or dynamic based on user config.
@@ -53,6 +54,8 @@ add_library(${LIBNAME} OBJECT
         bindings/c/memory_routines.cpp
         bindings/c/data_source/error_info.cpp
         bindings/c/logging/log_level.cpp
+        serialization/json_errors.cpp
+        serialization/json_value.cpp
         log_level.cpp
         config/persistence_builder.cpp
         config/logging_builder.cpp

libs/common/src/CMakeLists.txt

@@ -7,6 +7,10 @@
 #include <launchdarkly/detail/unreachable.hpp>
 #include <launchdarkly/value.hpp>
 
+#include <launchdarkly/detail/serialization/json_value.hpp>
+
+#include <boost/json.hpp>
+
 using launchdarkly::Value;
 
 #define AS_VALUE(x) reinterpret_cast<Value*>(x)
@@ -95,6 +99,18 @@ LD_EXPORT(unsigned int) LDValue_Count(LDValue val) {
     }
 }
 
+LD_EXPORT(char*) LDValue_SerializeJSON(LDValue val) {
+    LD_ASSERT_NOT_NULL(val);
+
+    auto const value = AS_VALUE(val);
+
+    auto boost_value = boost::json::value_from(*value);
+
+    std::string json = boost::json::serialize(boost_value);
+
+    return strdup(json.c_str());
+}
+
 LD_EXPORT(LDValue_ArrayIter) LDValue_ArrayIter_New(LDValue val) {
     LD_ASSERT_NOT_NULL(val);