Add support for list-template and list-empty widgets for specifying list widget templates (#7784)

Cherry picked from #7710

core/modules/widgets/list.js

@@ -60,6 +60,7 @@ ListWidget.prototype.render = function(parent,nextSibling) {
 Compute the internal state of the widget
 */
 ListWidget.prototype.execute = function() {
+	var self = this;
 	// Get our attributes
 	this.template = this.getAttribute("template");
 	this.editTemplate = this.getAttribute("editTemplate");
@@ -67,6 +68,8 @@ ListWidget.prototype.execute = function() {
 	this.counterName = this.getAttribute("counter");
 	this.storyViewName = this.getAttribute("storyview");
 	this.historyTitle = this.getAttribute("history");
+	// Look for <$list-template> and <$list-empty> widgets as immediate child widgets
+	this.findExplicitTemplates();
 	// Compose the list elements
 	this.list = this.getTiddlerList();
 	var members = [],
@@ -85,19 +88,49 @@ ListWidget.prototype.execute = function() {
 	this.history = [];
 };
 
+ListWidget.prototype.findExplicitTemplates = function() {
+	var self = this;
+	this.explicitListTemplate = null;
+	this.explicitEmptyTemplate = null;
+	var searchChildren = function(childNodes) {
+		$tw.utils.each(childNodes,function(node) {
+			if(node.type === "list-template") {
+				self.explicitListTemplate = node.children;
+			} else if(node.type === "list-empty") {
+				self.explicitEmptyTemplate = node.children;
+			} else if(node.type === "element" && node.tag === "p") {
+				searchChildren(node.children);
+			}
+		});
+	};
+	searchChildren(this.parseTreeNode.children);
+}
+
 ListWidget.prototype.getTiddlerList = function() {
+	var limit = $tw.utils.getInt(this.getAttribute("limit",""),undefined);
 	var defaultFilter = "[!is[system]sort[title]]";
-	return this.wiki.filterTiddlers(this.getAttribute("filter",defaultFilter),this);
+	var results = this.wiki.filterTiddlers(this.getAttribute("filter",defaultFilter),this);
+	if(limit !== undefined) {
+		if(limit >= 0) {
+			results = results.slice(0,limit);
+		} else {
+			results = results.slice(limit);
+		}
+	}
+	return results;
 };
 
 ListWidget.prototype.getEmptyMessage = function() {
 	var parser,
-		emptyMessage = this.getAttribute("emptyMessage","");
-	// this.wiki.parseText() calls 
-	// new Parser(..), which should only be done, if needed, because it's heavy!
-	if (emptyMessage === "") {
+		emptyMessage = this.getAttribute("emptyMessage");
+	// If emptyMessage attribute is not present or empty then look for an explicit empty template
+	if(!emptyMessage) {
+		if(this.explicitEmptyTemplate) {
+			return this.explicitEmptyTemplate;
+		} else {
 			return [];
 		}
+	}
 	parser = this.wiki.parseText("text/vnd.tiddlywiki",emptyMessage,{parseAsInline: true});
 	if(parser) {
 		return parser.tree;
@@ -122,9 +155,16 @@ ListWidget.prototype.makeItemTemplate = function(title,index) {
 	if(template) {
 		templateTree = [{type: "transclude", attributes: {tiddler: {type: "string", value: template}}}];
 	} else {
+		// Check for child nodes of the list widget
 		if(this.parseTreeNode.children && this.parseTreeNode.children.length > 0) {
+			// Check for a <$list-item> widget
+			if(this.explicitListTemplate) {
+				templateTree = this.explicitListTemplate;
+			} else if (!this.explicitEmptyTemplate) {
 				templateTree = this.parseTreeNode.children;
-		} else {
+			}
+		}
+		if(!templateTree) {
 			// Default template is a link to the title
 			templateTree = [{type: "element", tag: this.parseTreeNode.isBlock ? "div" : "span", children: [{type: "link", attributes: {to: {type: "string", value: title}}, children: [
 				{type: "text", text: title}

editions/test/tiddlers/tests/data/list-widget/WithExplicitTemplates.tid

@@ -0,0 +1,29 @@
+title: ListWidget/WithExplicitTemplates
+description: List widget with explicit templates
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
++
+title: Output
+
+\whitespace trim
+
+\procedure test(filter)
+<$list filter=<<filter>>>
+	<$list-template>
+		<$text text=<<currentTiddler>>/>
+	</$list-template>
+	<$list-empty>
+		None!
+	</$list-empty>
+</$list>
+\end
+
+<<test "1 2 3">>
+
+<<test "">>
+
++
+title: ExpectedResult
+
+<p>123</p><p>None!</p>

editions/test/tiddlers/tests/data/list-widget/WithExplicitTemplatesInBlockMode.tid

@@ -0,0 +1,32 @@
+title: ListWidget/WithExplicitTemplatesInBlockMode
+description: List widget with explicit templates in block mode
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
++
+title: Output
+
+\whitespace trim
+
+\procedure test(filter)
+<$list filter=<<filter>>>
+
+	<$list-template>
+		<$text text=<<currentTiddler>>/>
+	</$list-template>
+
+	<$list-empty>
+		None!
+	</$list-empty>
+
+</$list>
+\end
+
+<<test "1 2 3">>
+
+<<test "">>
+
++
+title: ExpectedResult
+
+123None!

editions/test/tiddlers/tests/data/list-widget/WithExplicitTemplatesOverriddenByAttributes.tid

@@ -0,0 +1,33 @@
+title: ListWidget/WithExplicitTemplatesOverriddenByAttributes
+description: List widget with explicit templates
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
++
+title: Output
+
+\whitespace trim
+
+\procedure test(filter)
+<$list filter=<<filter>> emptyMessage="Zero" template="Template">
+	<$list-template>
+		<$text text=<<currentTiddler>>/>
+	</$list-template>
+	<$list-empty>
+		None!
+	</$list-empty>
+</$list>
+\end
+
+<<test "1 2 3">>
+
+<<test "">>
+
++
+title: Template
+
+<$text text=<<currentTiddler>>/><$text text=<<currentTiddler>>/>
++
+title: ExpectedResult
+
+<p>112233</p><p>Zero</p>

editions/test/tiddlers/tests/data/list-widget/WithLimit.tid

@@ -0,0 +1,25 @@
+title: ListWidget/WithLimit
+description: List widget with limit
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
++
+title: Output
+
+Zero: <$list filter="1 2 3 4" limit="0" template="Template"/>
+
+One: <$list filter="1 2 3 4" limit="1" template="Template"/>
+
+Two: <$list filter="1 2 3 4" limit="2" template="Template"/>
+
+Minus Two: <$list filter="1 2 3 4" limit="-2" template="Template"/>
+
++
+title: Template
+
+<$text text=<<currentTiddler>>/>
++
+title: ExpectedResult
+
+<p>Zero: </p><p>One: 1</p><p>Two: 12</p><p>Minus Two: 34
+</p>

editions/test/tiddlers/tests/data/list-widget/WithMissingTemplate.tid

@@ -0,0 +1,26 @@
+title: ListWidget/WithMissingTemplate
+description: List widget with explicit templates
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
++
+title: Output
+
+\whitespace trim
+
+\procedure test(filter)
+<$list filter=<<filter>>>
+	<$list-empty>
+		None!
+	</$list-empty>
+</$list>
+\end
+
+<<test "1 2 3">>
+
+<<test "">>
+
++
+title: ExpectedResult
+
+<p><span><a class="tc-tiddlylink tc-tiddlylink-missing" href="#1">1</a></span><span><a class="tc-tiddlylink tc-tiddlylink-missing" href="#2">2</a></span><span><a class="tc-tiddlylink tc-tiddlylink-missing" href="#3">3</a></span></p><p>None!</p>

editions/tw5.com/tiddlers/widgets/ListWidget.tid

@@ -1,6 +1,6 @@
 caption: list
 created: 20131024141900000
-modified: 20230725203601441
+modified: 20230831182949930
 tags: Widgets Lists
 title: ListWidget
 type: text/vnd.tiddlywiki
@@ -70,6 +70,8 @@ See GroupedLists for how to generate nested and grouped lists using the ListWidg
 
 The content of the `<$list>` widget is an optional template to use for rendering each tiddler in the list.
 
+<<.from-version "5.3.2">> If the widgets `<$list-template>` or `<$list-empty>` are found as immediate children of the <<.wid "ListWidget">> widget then the content of those widgets are used as the list item template and/or the empty template. Note that the <<.attr "emptyMessage">> and <<.attr "template">> attributes take precedence if they are present.
+
 The action of the list widget depends on the results of the filter combined with several options for specifying the template:
 
 * If the filter evaluates to an empty list, the text of the ''emptyMessage'' attribute is rendered, and all other templates are ignored
@@ -79,6 +81,7 @@ The action of the list widget depends on the results of the filter combined with
 
 |!Attribute |!Description |
 |filter |The [[tiddler filter|Filters]] to display |
+|limit |<<.from-version "5.3.2">> Optional numeric limit for the number of results that are returned. Negative values will return the results from the end of the list |
 |template |The title of a template tiddler for transcluding each tiddler in the list. When no template is specified, the body of the ListWidget serves as the item template. With no body, a simple link to the tiddler is returned. |
 |editTemplate |An alternative template to use for [[DraftTiddlers|DraftMechanism]] in edit mode |
 |variable |The name for a [[variable|Variables]] in which the title of each listed tiddler is stored. Defaults to ''currentTiddler'' |