As someone who's been in a teaching role (in the Russian math circles for gifted children), I wouldn't have failed the student. My goal as a teacher is to make the student interested and competent. The student's objective is the same: to become interested and competent. Assignments and grades are means to that end, not an end in itself. If the student is already clearly interested and competent, and you make them lose interest by giving them a failing grade, you have sacrificed your top-level goal in favor of a class-centric subgoal that doesn't matter to anyone - or worse, sacrificed it to your selfish desire to avoid being ignored.
Maybe that sounded more callous than it was meant to. It's not about pride. I would talk to the student and explain why they didn't succeed. But I wouldn't give them a pass for ignoring the assignment.
Not carrying out the task assigned doesn't necessarily indicate interest or competence to me. Anybody can carry out a random task of their own choosing. The ability to successfully complete a problem put before you is much more valuable than the ability to complete some problem.
In particular, this assignment appears to have been as much about analyzing stack traces as anything else. He didn't demonstrate any competence in that area.
Personally, this is something I came to appreciate from my teachers. The ones who would let me just get away with anything as long as I made it look fancy bored me. I could literally get an A without knowing half the course material just by putting on a grand show. The ones who actually challenged me taught me a lot more. I can accomplish so much more when I'm not busy being an arrogant jerkoff.
