Macro define_context_function 

macro_rules! define_context_function {
    (
		$struct_name:ident,
		$func_name:literal,
		() -> $ret:ident,
		$impl_fn:expr
	) => { ... };
}

Define a context-aware scalar function that needs access to EvalContext.

Context-aware functions are not pure (they depend on session state) but are not async. They synchronously access context information like session::ns(), session::db(), etc.

Usage

// Function with no arguments that reads from context
define_context_function!(
    SessionNs,                      // Struct name
    "session::ns",                  // Function name
    () -> Any,                      // Signature: () -> return type
    session_ns_impl                 // Implementation function
);