MDL-55701 output: Adding core template for help_icon

We didn't intend to do this, but as I made the mistake of extending
core/help_icon in a core template without realising that it
works solely because I had that template in the new theme, I
decided to add this template to core too.

Part of MDL-55071

lib/outputcomponents.php

@@ -499,6 +499,8 @@ public function diag_strings() {
      * @return array
      */
     public function export_for_template(renderer_base $output) {
+        global $CFG;
+
         $title = get_string($this->identifier, $this->component);
 
         if (empty($this->linktext)) {
@@ -508,7 +510,16 @@ public function export_for_template(renderer_base $output) {
         }
 
         $data = get_formatted_help_string($this->identifier, $this->component, false);
+
         $data->alt = $alt;
+        $data->icon = (new pix_icon('help', $alt, 'core', ['class' => 'iconhelp']))->export_for_template($output);
+        $data->linktext = $this->linktext;
+        $data->title = get_string('helpprefix2', '', trim($title, ". \t"));
+        $data->url = (new moodle_url($CFG->httpswwwroot . '/help.php', [
+            'component' => $this->component,
+            'identifier' => $this->identifier,
+            'lang' => current_language()
+        ]))->out(false);
 
         $data->ltr = !right_to_left();
         return $data;

lib/outputrenderers.php

@@ -2412,39 +2412,7 @@ public function help_icon($identifier, $component = 'moodle', $linktext = '') {
      * @return string HTML fragment
      */
     protected function render_help_icon(help_icon $helpicon) {
-        global $CFG;
-
-        // first get the help image icon
-        $src = $this->pix_url('help');
-
-        $title = get_string($helpicon->identifier, $helpicon->component);
-
-        if (empty($helpicon->linktext)) {
-            $alt = get_string('helpprefix2', '', trim($title, ". \t"));
-        } else {
-            $alt = get_string('helpwiththis');
-        }
-
-        $attributes = array('src'=>$src, 'alt'=>$alt, 'class'=>'iconhelp');
-        $output = html_writer::empty_tag('img', $attributes);
-
-        // add the link text if given
-        if (!empty($helpicon->linktext)) {
-            // the spacing has to be done through CSS
-            $output .= $helpicon->linktext;
-        }
-
-        // now create the link around it - we need https on loginhttps pages
-        $url = new moodle_url($CFG->httpswwwroot.'/help.php', array('component' => $helpicon->component, 'identifier' => $helpicon->identifier, 'lang'=>current_language()));
-
-        // note: this title is displayed only if JS is disabled, otherwise the link will have the new ajax tooltip
-        $title = get_string('helpprefix2', '', trim($title, ". \t"));
-
-        $attributes = array('href' => $url, 'title' => $title, 'aria-haspopup' => 'true', 'target'=>'_blank');
-        $output = html_writer::tag('a', $output, $attributes);
-
-        // and finally span
-        return html_writer::tag('span', $output, array('class' => 'helptooltip'));
+        return $this->render_from_template('core/help_icon', $helpicon->export_for_template($this));
     }
 
     /**

lib/templates/help_icon.mustache

@@ -0,0 +1,22 @@
+{{!
+    This file is part of Moodle - http://moodle.org/
+
+    Moodle is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Moodle is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+}}
+{{!
+    Help icon.
+}}
+<span class="helptooltip">
+    <a href="{{url}}" title={{#quote}}{{title}}{{/quote}} aria-haspopup="true" target="_blank">{{#icon}}{{>core/pix_icon}}{{/icon}}{{#linktext}}{{.}}{{/linktext}}</a>
+</span>