Also make sure that the selection is preserved on the "Sets Manager"

page when the available options change.

htdocs/js/ProblemSetList/problemsetlist.js

@@ -286,6 +286,9 @@
 		const allOptions = Array.from(importSourceSelect.options);
 
 		const updateAvailableOptions = () => {
+			// Save the currently selected options.
+			const selectedDefs = Array.from(importSourceSelect.selectedOptions);
+
 			for (const option of Array.from(importSourceSelect.options)) option.value && option.remove();
 			for (const option of allOptions) {
 				if (option.value.startsWith('Library/')) {
@@ -294,6 +297,17 @@
 					if (listContribSetsCheck.checked) importSourceSelect.add(option);
 				} else importSourceSelect.add(option);
 			}
+
+			// Reselect the options that were selected before if still available. Otherwise
+			// select the first option which should be the "Select filenames below" option.
+			let foundSelected = false;
+			for (const option of importSourceSelect.options) {
+				if (selectedDefs.includes(option)) {
+					foundSelected = true;
+					option.selected = true;
+				}
+			}
+			if (!foundSelected) allOptions[0].selected = true;
 		};
 
 		listOPLSetsCheck?.addEventListener('change', updateAvailableOptions);

templates/ContentGenerator/Instructor/ProblemSetList/import_form.html.ep

@@ -15,7 +15,7 @@
 			class => 'col-form-label col-form-label-sm col-md-auto' =%>
 		<div class="col-auto">
 			<%= select_field 'action.import.source' => [
-					[ maketext('Enter filenames below') => '', selected => undef ],
+					[ maketext('Select filenames below') => '', selected => undef, disabled => undef ],
 					@$setDefList
 				],
 				id => 'import_source_select', class => 'form-select form-select-sm', dir => 'ltr',