AK+LibIPC: Add a convenience encoder/decoder for JsonValue

This requires that JsonValue is implicitly default-constructible.

AK/JsonValue.h

@@ -35,7 +35,8 @@ public:
 
     static ErrorOr<JsonValue> from_string(StringView);
 
-    explicit JsonValue(Type = Type::Null);
+    JsonValue() = default;
+    explicit JsonValue(Type);
     ~JsonValue() { clear(); }
 
     JsonValue(JsonValue const&);

Userland/Libraries/LibIPC/Decoder.cpp

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/JsonValue.h>
 #include <AK/MemoryStream.h>
 #include <AK/URL.h>
 #include <LibCore/AnonymousBuffer.h>
@@ -128,6 +129,14 @@ ErrorOr<void> Decoder::decode(ByteBuffer& value)
     return m_stream.try_handle_any_error();
 }
 
+ErrorOr<void> Decoder::decode(JsonValue& value)
+{
+    String string;
+    TRY(decode(string));
+    value = TRY(JsonValue::from_string(string));
+    return {};
+}
+
 ErrorOr<void> Decoder::decode(URL& value)
 {
     String string;

Userland/Libraries/LibIPC/Decoder.h

@@ -49,6 +49,7 @@ public:
     ErrorOr<void> decode(double&);
     ErrorOr<void> decode(String&);
     ErrorOr<void> decode(ByteBuffer&);
+    ErrorOr<void> decode(JsonValue&);
     ErrorOr<void> decode(URL&);
     ErrorOr<void> decode(Dictionary&);
     ErrorOr<void> decode(File&);

Userland/Libraries/LibIPC/Encoder.cpp

@@ -7,6 +7,8 @@
 
 #include <AK/BitCast.h>
 #include <AK/ByteBuffer.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
 #include <AK/String.h>
 #include <AK/URL.h>
 #include <LibCore/AnonymousBuffer.h>
@@ -159,6 +161,12 @@ Encoder& Encoder::operator<<(ByteBuffer const& value)
     return *this;
 }
 
+Encoder& Encoder::operator<<(JsonValue const& value)
+{
+    *this << value.serialized<StringBuilder>();
+    return *this;
+}
+
 Encoder& Encoder::operator<<(URL const& value)
 {
     return *this << value.to_string();

Userland/Libraries/LibIPC/Encoder.h

@@ -45,6 +45,7 @@ public:
     Encoder& operator<<(StringView);
     Encoder& operator<<(String const&);
     Encoder& operator<<(ByteBuffer const&);
+    Encoder& operator<<(JsonValue const&);
     Encoder& operator<<(URL const&);
     Encoder& operator<<(Dictionary const&);
     Encoder& operator<<(File const&);