Add "listed" filter operator for retrieving the tiddlers that list a specified tiddler

core/modules/filters/listed.js

@@ -0,0 +1,37 @@
+/*\
+title: $:/core/modules/filters/listed.js
+type: application/javascript
+module-type: filteroperator
+
+Filter operator returning all tiddlers that have the selected tiddlers in a list
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+/*
+Export our filter function
+*/
+exports.listed = function(source,operator,options) {
+	var results = [];
+	// Function to check an individual title
+	function checkTiddler(title) {
+		$tw.utils.pushTop(results,options.wiki.findListingsOfTiddler(title));
+	}
+	// Iterate through the source tiddlers
+	if($tw.utils.isArray(source)) {
+		$tw.utils.each(source,function(title) {
+			checkTiddler(title);
+		});
+	} else {
+		$tw.utils.each(source,function(element,title) {
+			checkTiddler(title);
+		});
+	}
+	return results;
+};
+
+})();

core/modules/wiki.js

@@ -415,13 +415,28 @@ exports.getTiddlersWithTag = function(tag) {
 	var titles = [];
 	for(var title in this.tiddlers) {
 		var tiddler = this.tiddlers[title];
-		if(tiddler.fields.tags && tiddler.fields.tags.indexOf(tag) !== -1) {
+		if($tw.utils.isArray(tiddler.fields.tags) && tiddler.fields.tags.indexOf(tag) !== -1) {
 			titles.push(title);
 		}
 	}
 	return this.sortByList(titles,tag);
 };
 
+/*
+Lookup a given tiddler and return a list of all the tiddlers that include it in their list
+*/
+exports.findListingsOfTiddler = function(targetTitle) {
+	// Get the list associated with the tag
+	var titles = [];
+	for(var title in this.tiddlers) {
+		var tiddler = this.tiddlers[title];
+		if($tw.utils.isArray(tiddler.fields.list) && tiddler.fields.list.indexOf(targetTitle) !== -1) {
+			titles.push(title);
+		}
+	}
+	return titles;
+};
+
 /*
 Sorts an array of tiddler titles according to an ordered list
 */