serde_json::Value::Null does not map to mlua::Value::Nil

[ElhamAryanpur]

When attempting to println!("{:#?}", lua.to_value(&serde_json::Value::Null)); the result is Userdata null instead of Lua's nil type. Every other data type is mapped correctly.

The mlua version tested with is 0.11.6 with "luajit, anyhow, async, macros, send, serialize, vendored" features enabled

[Kanaye]

That's a feature as otherwise you couldn't represent null in lua.
Because you can't distinguish between a key being nil or a key not existing.
That's why null is a light user data:

mlua/src/value.rs

Lines 76 to 79 in dc24217

	/// A special value (lightuserdata) to represent null value.
	///
	/// It can be used in Lua tables without downsides of `nil`.
	pub const NULL: Value = Value::LightUserData(LightUserData(ptr::null_mut()));

[ElhamAryanpur]

I am surprised personally that this is the default behavior. I would have expected the Nil to have been the default and optionally enable the null LightUserData if desired for distinguishing, due to the expectation of converting to Lua types. Could I ask the reasoning why its the other way around?