Fix [is[variable]] operator doesn't work for "fake" variables #6303 (#6996)

* Add tests for [is[variable]] and "faked" variables

See GH #6303

* Make is[variable] and variables[] operators resilient to fake widgets

Co-authored-by: jeremy@jermolene.com <jeremy@jermolene.com>

core/modules/filters/is/variable.js

@@ -19,13 +19,13 @@ exports.variable = function(source,prefix,options) {
 	var results = [];
 	if(prefix === "!") {
 		source(function(tiddler,title) {
-			if(!(title in options.widget.variables)) {
+			if(options.widget.getVariable(title) === undefined) {
 				results.push(title);
 			}
 		});
 	} else {
 		source(function(tiddler,title) {
-			if(title in options.widget.variables) {
+			if(options.widget.getVariable(title) !== undefined) {
 				results.push(title);
 			}
 		});

core/modules/filters/variables.js

@@ -16,9 +16,15 @@ Filter operator for returning the names of the active variables
 Export our filter function
 */
 exports.variables = function(source,operator,options) {
-	var names = [];
+	var names = [],
-	for(var variable in options.widget.variables) {
+		widget = options.widget;
-		names.push(variable);
+	while(widget && !widget.hasOwnProperty("variables")) {
+		widget = widget.parentWidget;
+	}
+	if(widget && widget.variables) {
+		for(var variable in widget.variables) {
+			names.push(variable);
+		}
 	}
 	return names.sort();
 };

editions/test/tiddlers/tests/data/filters/fake-variables.tid

@@ -0,0 +1,27 @@
+title: Filters/FakeVariables
+description: Test for https://github.com/Jermolene/TiddlyWiki5/issues/6303
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\whitespace trim
+<$list variable="var" filter="[[existing variable should have output]] :filter[[..currentTiddler]is[variable]]">
+<p><<var>></p>
+</$list>
+
+<$list variable="var" filter="[[non-existing variable should not have output]] :filter[[nonExistingVariable]is[variable]]">
+<p><<var>></p>
+</$list>
+
+<$list variable="var" filter="[[existing variable negated should not have output]] :filter[[..currentTiddler]!is[variable]]">
+<p><<var>></p>
+</$list>
+
+<$list variable="var" filter="[[non-existing variable negated should have output]] :filter[[nonExistingVariable]!is[variable]]">
+<p><<var>></p>
+</$list>
++
+title: ExpectedResult
+
+<p><p>existing variable should have output</p></p><p></p><p></p><p><p>non-existing variable negated should have output</p></p>