formatters/JSON: Prepare to remove rapidjson from installed Zeek headers

threading/formatters/JSON.h currently includes rapidjson headers for declaring
the NullDoubleWriter. This appears mostly an internal detail, but
results in the situation that 1) we need to ship rapidjson headers with
the Zeek install tree and 2) taking care that external plugins are able
to find these headers should they include formatters/JSON.h.

There are currently no other Zeek headers that include rapidjson, so this
seems very unfortunate and self-inflicted given it's not actually required.

Attempt to hide this implementation detail with the goal to remove the
rapidjson includes with v7.1 and then also stop bundling and exposing
the include path to external plugins.

The NullDoubleWriter implementation moves into a new formatters/detail/json.h
header which is not installed.

Closes #3128

src/CMakeLists.txt

@@ -602,6 +602,8 @@ install(
     PATTERN "*.h"
     PATTERN "*.pac"
     PATTERN "3rdparty/*" EXCLUDE
+    # Headers used only during build
+    PATTERN "threading/formatters/detail" EXCLUDE
     # The "zeek -> ." symlink isn't needed in the install-tree
     REGEX "${escaped_include_path}$" EXCLUDE
     # FILES_MATCHING creates empty directories:

src/Val.cc

@@ -39,7 +39,7 @@
 #include "zeek/broker/Data.h"
 #include "zeek/broker/Manager.h"
 #include "zeek/broker/Store.h"
-#include "zeek/threading/formatters/JSON.h"
+#include "zeek/threading/formatters/detail/json.h"
 
 using namespace std;
 
@@ -404,8 +404,8 @@ TableValPtr Val::GetRecordFields()
 
 // This is a static method in this file to avoid including rapidjson's headers in Val.h because
 // they're huge.
-static void BuildJSON(threading::formatter::JSON::NullDoubleWriter& writer, Val* val,
-                      bool only_loggable = false, RE_Matcher* re = nullptr, const string& key = "")
+static void BuildJSON(json::detail::NullDoubleWriter& writer, Val* val, bool only_loggable = false,
+                      RE_Matcher* re = nullptr, const string& key = "")
 	{
 	if ( ! key.empty() )
 		writer.Key(key);
@@ -509,7 +509,7 @@ static void BuildJSON(threading::formatter::JSON::NullDoubleWriter& writer, Val*
 				else
 					{
 					rapidjson::StringBuffer buffer;
-					threading::formatter::JSON::NullDoubleWriter key_writer(buffer);
+					json::detail::NullDoubleWriter key_writer(buffer);
 					BuildJSON(key_writer, entry_key, only_loggable, re);
 					string key_str = buffer.GetString();
 
@@ -612,7 +612,7 @@ static void BuildJSON(threading::formatter::JSON::NullDoubleWriter& writer, Val*
 StringValPtr Val::ToJSON(bool only_loggable, RE_Matcher* re)
 	{
 	rapidjson::StringBuffer buffer;
-	threading::formatter::JSON::NullDoubleWriter writer(buffer);
+	json::detail::NullDoubleWriter writer(buffer);
 
 	BuildJSON(writer, this, only_loggable, re, "");
 

src/threading/formatters/JSON.cc

@@ -16,10 +16,12 @@
 
 #include "zeek/Desc.h"
 #include "zeek/threading/MsgThread.h"
+#include "zeek/threading/formatters/detail/json.h"
 
 namespace zeek::threading::formatter
 	{
 
+// For deprecated NullDoubleWriter
 bool JSON::NullDoubleWriter::Double(double d)
 	{
 	if ( rapidjson::internal::Double(d).IsNanOrInf() )
@@ -39,7 +41,7 @@ JSON::~JSON() { }
 bool JSON::Describe(ODesc* desc, int num_fields, const Field* const* fields, Value** vals) const
 	{
 	rapidjson::StringBuffer buffer;
-	NullDoubleWriter writer(buffer);
+	zeek::json::detail::NullDoubleWriter writer(buffer);
 
 	writer.StartObject();
 
@@ -68,7 +70,7 @@ bool JSON::Describe(ODesc* desc, Value* val, const std::string& name) const
 
 	rapidjson::Document doc;
 	rapidjson::StringBuffer buffer;
-	NullDoubleWriter writer(buffer);
+	zeek::json::detail::NullDoubleWriter writer(buffer);
 
 	writer.StartObject();
 	BuildJSON(writer, val, name);
@@ -85,7 +87,8 @@ Value* JSON::ParseValue(const std::string& s, const std::string& name, TypeTag t
 	return nullptr;
 	}
 
-void JSON::BuildJSON(NullDoubleWriter& writer, Value* val, const std::string& name) const
+void JSON::BuildJSON(zeek::json::detail::NullDoubleWriter& writer, Value* val,
+                     const std::string& name) const
 	{
 	if ( ! name.empty() )
 		writer.Key(name);

src/threading/formatters/JSON.h

@@ -3,11 +3,18 @@
 #pragma once
 
 #define RAPIDJSON_HAS_STDSTRING 1
+// Remove in v7.1 when removing NullDoubleWriter below and also remove
+// rapidjson include tweaks from  CMake's dynamic_plugin_base target.
 #include <rapidjson/document.h>
 #include <rapidjson/writer.h>
 
 #include "zeek/threading/Formatter.h"
 
+namespace zeek::json::detail
+	{
+class NullDoubleWriter;
+	}
+
 namespace zeek::threading::formatter
 	{
 
@@ -38,7 +45,8 @@ public:
 	class NullDoubleWriter : public rapidjson::Writer<rapidjson::StringBuffer>
 		{
 	public:
-		NullDoubleWriter(rapidjson::StringBuffer& stream)
+		[[deprecated("Remove in v7.1 - This is an implementation detail.")]] NullDoubleWriter(
+			rapidjson::StringBuffer& stream)
 			: rapidjson::Writer<rapidjson::StringBuffer>(stream)
 			{
 			}
@@ -46,7 +54,8 @@ public:
 		};
 
 private:
-	void BuildJSON(NullDoubleWriter& writer, Value* val, const std::string& name = "") const;
+	void BuildJSON(zeek::json::detail::NullDoubleWriter& writer, Value* val,
+	               const std::string& name = "") const;
 
 	TimeFormat timestamps;
 	bool surrounding_braces;

src/threading/formatters/detail/json.h

@@ -0,0 +1,27 @@
+// Not installed - used by Val.cc and formatters/JSON.cc only.
+#pragma once
+
+#include <rapidjson/document.h>
+#include <rapidjson/internal/ieee754.h>
+#include <rapidjson/writer.h>
+
+namespace zeek::json::detail
+	{
+// A rapidjson Writer that writes null for inf or nan numbers.
+class NullDoubleWriter : public rapidjson::Writer<rapidjson::StringBuffer>
+	{
+public:
+	explicit NullDoubleWriter(rapidjson::StringBuffer& stream)
+		: rapidjson::Writer<rapidjson::StringBuffer>(stream)
+		{
+		}
+	bool Double(double d)
+		{
+		if ( rapidjson::internal::Double(d).IsNanOrInf() )
+			return rapidjson::Writer<rapidjson::StringBuffer>::Null();
+
+		return rapidjson::Writer<rapidjson::StringBuffer>::Double(d);
+		}
+	};
+
+	}