attrParser.m

function [res, extra_c, unmatched] = attrParser(dflt, argPairs_c, KeepUnmatched)
% A naive way to parse argument
% It may not be a good idea enable this function to parse an obj. For objects,
% setting an attribute is allowed to affect its another attribute. Therefore the
% order of setting, which is unknown to this function, matters.
import attr.*

if nargin == 0, test(); return; end

if isobject(dflt), KeepUnmatched = false; end
if ~exist('KeepUnmatched','var'), KeepUnmatched = true; end

if iscell(argPairs_c) && numel(argPairs_c)==1, argPairs_c = argPairs_c{1}; end

attr_c = attrs(dflt);
if isstruct(argPairs_c) || isobject(argPairs_c)
  [~, res, unmatched] = mrgattrs(argPairs_c, dflt);
  if ~(KeepUnmatched || isempty(attrs(unmatched)))
    error(struct('identifier','MATLAB:InputParser:UnmatchedParameter'));
  end
elseif iscell(argPairs_c)
  p = inputParser; % inputParser has no constructor.
  p.KeepUnmatched = KeepUnmatched;

  values_c = getattrs(dflt, attr_c);

  % may adapt fancier init in the future
  for ia = 1:numel(attr_c), addOptional(p, attr_c{ia}, values_c{ia}); end

  parse(p, argPairs_c{:});
  [res, unmatched] = deal(p.Results, p.Unmatched);
else, error('Unsupported parsing input');
end

extra_c = reshape(attrs(unmatched), 1, []); % ensuring row cell vector
if ~isempty(extra_c)
  extra_c = reshape([extra_c; getattrs(unmatched, extra_c)], 1, []);
end

end

function test()
prefix = mfilename('fullpath');
disp('----------------------');
disp([prefix, '.test()']);

[x,   y,   z] = deal(3, 4, 5);
[a.x, a.y]    = deal(1, 2);
arg_pairs_c = {'x', x, 'y', y};

[~, extra_c, unmatched] = attrParser(a, struct(arg_pairs_c{:}));
disp('--  test: w/o extra:  --');
disp('extra_c: (expect no output for this)');
disp(extra_c);
disp('unmatched:');
disp(unmatched);

KeepUnmatched = false;
arg_pairs_c = [arg_pairs_c, {'z', z}];
try attrParser(a, struct(arg_pairs_c{:}), KeepUnmatched);
catch ME % MATLAB ERROR
  if ~strcmp(ME.identifier,'MATLAB:InputParser:UnmatchedParameter')
    disp([prefix, '.test() failed']); rethrow(ME);
  end
end
try [res, extra_c] = attrParser(a, arg_pairs_c, KeepUnmatched);
catch ME % MATLAB ERROR
  if strcmp(ME.identifier,'MATLAB:InputParser:UnmatchedParameter')
    [res, extra_c, unmatched] = attrParser(a, [arg_pairs_c, {'z',z}], true);
  else, disp([prefix, '.test() failed']); rethrow(ME);
  end
end
disp('--  test: w/ extra:  --');
disp('matched:');
disp(res);
assert(isequal(res, struct('x',x,'y',y)), 'attrParser: res test failed');
disp('extra_c:');
disp(extra_c);
assert(isequal(extra_c, {'z',z}), 'attrParser: extra_c test failed');
disp('unmatched:');
disp(unmatched);
assert(isequal(unmatched, struct('z',z)), 'attrParser: unmatched test failed');

disp([prefix, '.test() passed']);

end