Workaround equivalent of "inputname" to return structure name? - matlab

Question

I know that, inside a MATLAB function, inputname(k) will return the k-th argument iff the argument is a variable name. Is there any way to write some parsing code that can retrieve the full input argument when that argument is a structure, e.g. foo.bar ? The reason I want to be able to do this is that I'm writing some tools for generic use where the input could be either a named variable or a named structure element.
My primary intent is to be able to store and return the input argment(s) as part of a structure or other variable that the function returns. This is a 'chain of custody' feature which makes it easier for me or others to verify the source data sets used to generate the output data sets.
I don't want the user to have to self-parse externally, or to have to deal with some kludge like
function doit(name,fieldname)
if(exist('fieldname','var'))
name = name.(fieldname);
myinput = [inputname(1),inputname(2)];
else
myinput = inputname(1);
end
% do the function stuff
(I call this a kludge because it both requires the user to enter strange arguments and because it fouls up the argument sequence for functions with multiple inputs)

Answer 1

There is no support from the language to get the input names when passing structs. The reason is probably x.a is internally a call to subsref which returns a new variable, all context is lost. The only possibility you have is using the debug tools and parse the code. There is no other option.
function x=f(varargin)
[ST, I] = dbstack('-completenames', 1);
if numel(ST)>0
fid=fopen(ST(1).file,'r');
for ix=2:ST(1).line;fgetl(fid);end
codeline=fgetl(fid);
fclose(fid);
fprintf('function was called with line %s\n',codeline);
else
fprintf('function was called from base workspace\n');
end
end
From there you may try to parse the code line to get the individual argument names.

Answer 2

Far uglier than Daniel's approach, and probably will crash on the wrong OS, but here's a hack that works to retrieve the first argument; easily adjusted to retrieve all arguments.
[~,myname] = system('whoami');
myname = strtrim(myname(4:end)); % removes domain tag in my Windows envir
% sorry about " \' " fouling up SO's color parsing
myloc = ['C:\Users\' , myname , '\AppData\Roaming\MathWorks\MATLAB\R2015a\History.xml'] ;
f = fopen(myloc,'r');
foo = fscanf(f,'%s');
fclose(f);
pfoo = findpat(foo,'myFunctionName');
% just look for the last instance
namstart = find(foo(pfoo(end):(pfoo(end)+30)) =='(',1) +pfoo(end);
% catch either ')' or ','
namend(1) = find(foo((namstart):end)== ')',1) -2 +namstart;
if numel(find(foo((namstart):end)== ',',1)),
namend(2) = find(foo((namstart):end)== ',',1) -2 +namstart;
end
thearg = foo(namstart:(min(namend)) );