Reselect the selected set definition file after re-adding the options.

The default disabled "Select a Set Definition File" needs to always be
present so that if an option is no longer available due to one of the
"List OPL Sets" or "List Contrib Sets" check boxes being unchecked after
selecting one of those set definition files, then the default can be
selected again.

htdocs/js/SetMaker/setmaker.js

@@ -519,14 +519,24 @@
 		const allOptions = Array.from(setDefSelect.options);
 
 		const updateAvailableOptions = () => {
+			// Save the currently selected option.
+			let selectedDef = setDefSelect.selectedOptions[0];
+
 			for (const option of Array.from(setDefSelect.options)) option.value && option.remove();
 			for (const option of allOptions) {
 				if (option.value.startsWith('Library/')) {
 					if (listOPLSetsCheck.checked) setDefSelect.add(option);
+					else if (selectedDef === option) selectedDef = null;
 				} else if (option.value.startsWith('Contrib/')) {
 					if (listContribSetsCheck.checked) setDefSelect.add(option);
+					else if (selectedDef === option) selectedDef = null;
 				} else setDefSelect.add(option);
 			}
+
+			// Reselect the option that was selected before if it is still available. Otherwise
+			// select the first option which should be the "Select a Set Defintion File" option.
+			if (selectedDef) selectedDef.selected = true;
+			else allOptions[0].selected = true;
 		};
 
 		listOPLSetsCheck?.addEventListener('change', updateAvailableOptions);

templates/ContentGenerator/Instructor/SetMaker/browse_setdef_panel.html.ep

@@ -15,9 +15,11 @@
 	<div class="mb-2">
 		<label class="col-form-label-sm"><%= maketext('Browse from:') %></label>
 		<%= select_field library_sets => [
-				$selected_library eq '' ?
-					[ maketext('Select a Set Definition File') => '', selected => undef, disabled => 'disabled' ]
-					: (),
+				[
+					maketext('Select a Set Definition File') => '',
+					$selected_library ? () : (selected => undef),
+					disabled => undef
+				],
 				@list_of_set_defs
 			],
 			class => 'form-select form-select-sm d-inline w-auto' =%>