Allow grading in parts with empty input.

[shinuito]

Hi,

This issue has come up at least twice that I can see on the Moodle forums, in 2018 and recently in September 2020. Just to continue and move a discussion from there to here, which seems more appropriate. A brief summary of the issue below.

At the moment, it is very convenient to use the multiple input in parts of a formulas type question, both to align the display of the parts, and also to do combined grading on the parts of the question. For example I can align MCE type and input type boxes as below so that it looks like a student can input say an interval or set of real numbers with two elements as an answer. It can be a bit tricky to get students to input expressions like [a,b] into an input box and compare it, either with regular expressions or in another question type like STACK (even though they have commands like cc(a,b) that they recognise). There's lots of tradeoffs between ease of input and ease of parsing the answer and grading it.

However there is a huge drawback. Suppose the four input boxes belong to the same part say {#1} and are displayed like {_0:choices:MCE}{_1} , {_2} {_3:choices2:MCE}, then since the answer is for example a numerical list [0,1,2,0] etc. If any of the four input boxes are left empty (as is likely to be the case, students do it all the time on paper assignments), the grading variables and marking are completely skipped and the answer is marked wrong.

Now the possible work arounds are quite involved, especially if we assume the average person making the questions, just wants to use the WYSIWYG editors, learning minimal syntax for inserting parts/input boxes etc (The moodleformulas website is quite good at explaining these things). For instance one has to split the four input boxes above into four separate parts, manually edit the html display style, to get them to align, and now in theory you can get marks for each input even if other boxes are blank. That is unless the grading of the inputs are codependent. For instance imagine the answer is a set and you would like the student to be able to input either {0,1} or {1,0}. Now you can't really just split them into multiple parts, and some workarounds might involve javascript to copy inputs into hidden extra inputs.

Typically having to suggest one workaround to an issue will lead to many more workarounds needed. For instance, even getting the question to display the same using div inline, once the question is answered, the separate parts display their own feedback and that already destroys the html display, in a way it wouldn't if they were all one part

It would be great if there was a way to either ignore blank input boxes. One could have a special character/comparison or function that could check if the inputs were empty, but nonetheless proceed to the grading, so that parts with multiple inputs can be marked even if some inputs are empty.

If it is too much of a change that it could break old questions, then maybe allow this as a setting/toggle/checkbox which either keeps the old way, or allows empty inputs to still proceed to grading.