Active elements output empty

[lainets]

The manual's active elements example is supposed to echo back the input but the output is left empty. The problem is not yet on production but can be found on minus: https://minus.cs.aalto.fi/aplus-manual/master/active_elements/introduction/.

Commit ad95bc9 changes the URL being polled to be configured through a HTML attribute but the URL hasn't been configured for active elements. Furthermore, active elements wants to poll the submission but the submission doesn't exist when the page is loaded, so the URL isn't known until after the page is loaded when the submission is made.

Edit: Note that the output will show up after reloading the page.

[markkuriekkinen]

Furthermore, active elements wants to poll the submission but the submission doesn't exist when the page is loaded, so the URL isn't known until after the page is loaded when the submission is made.

This isn't a problem since the old active element code in chapter.js already picks the submission feedback poll URL from the HTTP response to the submit POST request. The initial "waiting for grading" feedback contains the URL for the (newly created) submission.

a-plus/exercise/static/exercise/chapter.js

Lines 605 to 608 in f14b0de

	const poll_url = content.find(".exercise-wait").attr("data-poll-url");
	output.attr('data-poll-url', poll_url);
	const ready_url = content.find(".exercise-wait").attr("data-ready-url");
	output.attr('data-ready-url', ready_url);

(The linked version above already contains the new fix too.)