​function arguments are not PG_FUNCTION_ARGS, how to pass Node *escontext

hi. simple question....

The following one works.
------------------------------------------------------------
Datum
test_direct_inputcall(PG_FUNCTION_ARGS)
{
char *token = PG_GETARG_CSTRING(0);
Datum numd;
if (!DirectInputFunctionCallSafe(numeric_in, token,
InvalidOid, -1,
fcinfo->context,
&numd))
{
elog(INFO,"convert to cstring failed");
PG_RETURN_BOOL(false);
}
elog(INFO,"%s",DatumGetCString(DirectFunctionCall1(numeric_out,numd)));
PG_RETURN_BOOL(true);
}
------------------------------------------------------------
--the following one does not work. will print out something is wrong

Datum
test_direct_inputcall(PG_FUNCTION_ARGS)
{
char *token = PG_GETARG_CSTRING(0);
Datum numd;
numd = return_numeric_datum(token);
elog(INFO,"%s",DatumGetCString(DirectFunctionCall1(numeric_out,numd)));
PG_RETURN_BOOL(true);
}

static
Datum return_numeric_datum(char *token)
{
Datum numd;
Node *escontext;

if (!DirectInputFunctionCallSafe(numeric_in, token,
InvalidOid, -1,
escontext,
&numd));
elog(INFO,"something is wrong");
return numd;
}
------------------------------------------------------------
I wonder how to make it return_numeric_datum works in functions that
arguments are not PG_FUNCTION_ARGS.

To make it work, I need to understand the Node *context, which is kind
of a vague idea for me.
In the top level function (input as PG_FUNCTION_ARGS) the Node
*context can be used to print out errors and back to normal state, I
kind of get it.

I really appreciate someone showing a minimal, reproducible example
based on return_numeric_datum....