Transclude widget should use fallback content if variable is missing or blank

Fixes #7424

core/modules/widgets/macrocall.js

@@ -51,7 +51,8 @@ MacroCallWidget.prototype.execute = function() {
 	var positionalName = 0,
 		parseTreeNodes = [{
 			type: "transclude",
-			isBlock: this.parseTreeNode.isBlock
+			isBlock: this.parseTreeNode.isBlock,
+			children: this.parseTreeNode.children
 		}];
 	$tw.utils.addAttributeToParseTreeNode(parseTreeNodes[0],"$variable",this.macroName);
 	$tw.utils.addAttributeToParseTreeNode(parseTreeNodes[0],"$type",this.parseType);

core/modules/widgets/transclude.js

@@ -171,11 +171,12 @@ TranscludeWidget.prototype.getTransclusionTarget = function() {
 	}
 	var parser;
 	// Get the parse tree
+	if(this.hasAttribute("$variable")) {
 		if(this.transcludeVariable) {
 			// Transcluding a variable
 			var variableInfo = this.getVariableInfo(this.transcludeVariable,{params: this.getOrderedTransclusionParameters()}),
 				srcVariable = variableInfo && variableInfo.srcVariable;
-		if(srcVariable) {
+			if(variableInfo.text) {
 				if(srcVariable.isFunctionDefinition) {
 					// Function to return parameters by name or position
 					var fnGetParam = function(name,index) {
@@ -267,6 +268,7 @@ TranscludeWidget.prototype.getTransclusionTarget = function() {
 					}
 				}
 			}
+		}
 	} else {
 		// Transcluding a text reference
 		parser = this.wiki.parseTextReference(

editions/test/tiddlers/tests/data/transclude/Macro-Missing.tid

@@ -0,0 +1,40 @@
+title: Transclude/Macro/Missing
+description: Transcluding a missing or blank variable
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\whitespace trim
+<$macrocall $name="missingmacro">
+Fallback content
+</$macrocall>
+
+<$transclude $variable="missingmacro">
+Fallback content
+</$transclude>
+
+<$macrocall $name="">
+Fallback content
+</$macrocall>
+
+<$transclude $variable="">
+Fallback content
+</$transclude>
+
+<$let emptyVariable="">
+
+<$macrocall $name="emptyVariable">
+Fallback content
+</$macrocall>
+
+<$transclude $variable="emptyVariable">
+Fallback content
+</$transclude>
+
+</$let>
+
++
+title: ExpectedResult
+
+<p>Fallback content</p><p>Fallback content</p><p>Fallback content</p><p>Fallback content</p><p>Fallback content</p><p>Fallback content</p>