Can't extract from nested JSON

[nicksterious]

Describe the bug
I am getting a compile error when trying to extract a portion of a nested JSON document.

Troubleshooter report
Here is the report generated by the ArduinoJson Troubleshooter:

ArduinoJson Troubleshooter's report

1. The issue happens at compile time
2. The error is not in the list

Environment
Here is the environment that I used:

• Microcontroller: RP2040
• Core/runtime: arduino mbed
• IDE: VSCode/platformio

Reproduction
Here is a small snippet that reproduces the issue.

{
  "state": {
    "desired": {
      "welcome": "aws-iot",
      "powerState": "OFF"
    },
    "reported": {
      "welcome": "aws-iot",
      "powerState": "OFF"
    }
  },
  "metadata": {
    "desired": {
      "welcome": {
        "timestamp": 1647421659
      },
      "powerState": {
        "timestamp": 1647594171
      }
    },
    "reported": {
      "welcome": {
        "timestamp": 1647421659
      },
      "powerState": {
        "timestamp": 1647594576
      }
    }
  },
  "version": 531,
  "timestamp": 1647620956
}

  DynamicJsonDocument incoming_message(2048);
  DynamicJsonDocument thing_state(2048);
  deserializeJson(incoming_message, incoming_message_str);
  thing_state = incoming_message["state"];
  // at this point thing_state should contain the "state" but not the "metadata"

Compiler output

.pio\libdeps\pico\ArduinoJson\src/ArduinoJson/Document/BasicJsonDocument.hpp:100:31: error: 'const class ArduinoJson6193_F1::MemberProxy<ArduinoJson6193_F1::JsonDocument&, const char*>' has no member named 'memoryUsage'
  100 |     size_t requiredSize = src.memoryUsage();
      |                           ~~~~^~~~~~~~~~~
*** [.pio\build\pico\src\main.cpp.o] Error 1

Expected output:
Program should compile and maybe work.

[bblanchon]

Hi @nicksterious,

Thank you very much for reporting this bug.
I'm going to fix it soon; meanwhile, please use the following workaround:

thing_state = incoming_message["state"].as<JsonVariant>();

Best regards,
Benoit

[bblanchon]

The fix was released with ArduinoJson 6.19.4.