Support Mustache partials in Mustache template module

* Add template partial support which matches the server-side implementation
  and means that we have full mustache support.

https://mustache.github.io/mustache.5.html#Partials

Bug: T97188
Change-Id: Ic752f52669dbffa21c4a514509c3ea1da8ac5d9c

resources/src/mediawiki/mediawiki.template.mustache.js

@@ -4,8 +4,27 @@
 	mw.template.registerCompiler( 'mustache', {
 		compile: function ( src ) {
 			return {
-				render: function ( data ) {
-					return $( $.parseHTML( Mustache.render( src, data ) ) );
+				/**
+				 * @ignore
+				 * @return {string} The raw source code of the template
+				 */
+				getSource: function () {
+					return src;
+				},
+				/**
+				 * @ignore
+				 * @param {Object} data Data to render
+				 * @param {Object} partialTemplates Map partial names to Mustache template objects
+				 *  returned by mw.template.get()
+				 */
+				render: function ( data, partialTemplates ) {
+					var partials = {};
+					if ( partialTemplates ) {
+						$.each( partialTemplates, function ( name, template ) {
+							partials[ name ] = template.getSource();
+						} );
+					}
+					return $( $.parseHTML( Mustache.render( src, data, partials ) ) );
 				}
 			};
 		}

tests/phpunit/data/templates/conds.mustache

@@ -0,0 +1 @@
+{{#list}}oh no{{/list}}{{#foo}}none of this should render{{/foo}}

tests/qunit/QUnitTestResources.php

@@ -71,6 +71,7 @@ return array(
 			'tests/qunit/suites/resources/mediawiki/mediawiki.RegExp.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.storage.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.template.test.js',
+			'tests/qunit/suites/resources/mediawiki/mediawiki.template.mustache.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.html.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.Title.test.js',
@@ -126,6 +127,7 @@ return array(
 			'mediawiki.toc',
 			'mediawiki.Uri',
 			'mediawiki.user',
+			'mediawiki.template.mustache',
 			'mediawiki.template',
 			'mediawiki.util',
 			'mediawiki.special.recentchanges',

tests/qunit/suites/resources/mediawiki/mediawiki.template.mustache.test.js

@@ -0,0 +1,32 @@
+( function ( mw ) {
+
+	QUnit.module( 'mediawiki.template.mustache', {
+		setup: function () {
+			// Stub register some templates
+			this.sandbox.stub( mw.templates, 'get' ).returns( {
+				'test_greeting.mustache': '<div>{{foo}}{{>suffix}}</div>',
+				'test_greeting_suffix.mustache': ' goodbye'
+			} );
+		}
+	} );
+
+	QUnit.test( 'render', 2, function ( assert ) {
+		var html, htmlPartial, data, partials,
+			template = mw.template.get( 'stub', 'test_greeting.mustache' ),
+			partial = mw.template.get( 'stub', 'test_greeting_suffix.mustache' );
+
+		data = {
+			foo: 'Hello'
+		};
+		partials = {
+			suffix: partial
+		};
+
+		html = template.render( data ).html();
+		htmlPartial = template.render( data, partials ).html();
+
+		assert.strictEqual( html, 'Hello', 'Render without partial' );
+		assert.strictEqual( htmlPartial, 'Hello goodbye', 'Render with partial' );
+	} );
+
+}( mediaWiki ) );