I have written a Matlab R2020b script that optionally receives three inputs – but if the inputs are not received, they are set to the defaults within the script.

function my_func(varargin)
    user_inputs = inputParser;
    addOptional(user_inputs, 'input1', getinput1());
    addOptional(user_inputs, 'input2', getinput2());
    addOptional(user_inputs, 'input3', getinput3());
    
    parse(user_inputs, varargin{:});
    input1 = user_inputs.Results.input1;
    input2 = user_inputs.Results.input2;
    input3 = user_inputs.Results.input3; 

    % definitions for the get input functions are here, but aren't important to my question

end

Here, the functions getinput1(), getinput2(), and getinput3() are used to generate the appropriate default values.

My intent is to allow the user to call the function with or without the inputs. When I call the function without inputs, it works correctly, but when I call the function with all three inputs as

my_func('myfirstinput', 'mysecondinput', 'mythirdinput')

then I get the error:

Error using my_func
Too many input arguments

What is causing this error, and how do I correctly call a function while incorporating its optional parameters?