MDL-42989 Admin: Clean output when building site administration tree for JS

Previously, any inappropriate whitespace found whilst building the admin
tree caused a JSON error and for the site administration tree retrieval to
fail.

This change ensures that access to the site administration tree is unbroken
for non-developers, whilst still alerting developers that there is an
issue.

blocks/navigation/yui/build/moodle-block_navigation-navigation/moodle-block_navigation-navigation-debug.js

@@ -649,6 +649,12 @@ BRANCH.prototype = {
         this.node.setAttribute('data-loaded', '1');
         try {
             var object = Y.JSON.parse(outcome.responseText);
+            if (object.error) {
+                Y.use('moodle-core-notification-ajaxException', function () {
+                    return new M.core.ajaxException(object).show();
+                });
+                return false;
+            }
             if (object.children && object.children.length > 0) {
                 var coursecount = 0;
                 for (var i in object.children) {
@@ -672,9 +678,14 @@ BRANCH.prototype = {
                 return true;
             }
             Y.log('AJAX loading complete but there were no children.', 'note', 'moodle-block_navigation');
-        } catch (ex) {
+        } catch (error) {
             // If we got here then there was an error parsing the result.
             Y.log('Error parsing AJAX response or adding branches to the navigation tree', 'error', 'moodle-block_navigation');
+            Y.use('moodle-core-notification-exception', function () {
+                return new M.core.exception(error).show();
+            });
+
+            return false;
         }
         // The branch is empty so class it accordingly
         this.node.replaceClass('branch', 'emptybranch');

blocks/navigation/yui/build/moodle-block_navigation-navigation/moodle-block_navigation-navigation.js

@@ -647,6 +647,12 @@ BRANCH.prototype = {
         this.node.setAttribute('data-loaded', '1');
         try {
             var object = Y.JSON.parse(outcome.responseText);
+            if (object.error) {
+                Y.use('moodle-core-notification-ajaxException', function () {
+                    return new M.core.ajaxException(object).show();
+                });
+                return false;
+            }
             if (object.children && object.children.length > 0) {
                 var coursecount = 0;
                 for (var i in object.children) {
@@ -668,8 +674,13 @@ BRANCH.prototype = {
                 }
                 return true;
             }
-        } catch (ex) {
+        } catch (error) {
             // If we got here then there was an error parsing the result.
+            Y.use('moodle-core-notification-exception', function () {
+                return new M.core.exception(error).show();
+            });
+
+            return false;
         }
         // The branch is empty so class it accordingly
         this.node.replaceClass('branch', 'emptybranch');

blocks/navigation/yui/src/navigation/js/navigation.js

@@ -647,6 +647,12 @@ BRANCH.prototype = {
         this.node.setAttribute('data-loaded', '1');
         try {
             var object = Y.JSON.parse(outcome.responseText);
+            if (object.error) {
+                Y.use('moodle-core-notification-ajaxException', function () {
+                    return new M.core.ajaxException(object).show();
+                });
+                return false;
+            }
             if (object.children && object.children.length > 0) {
                 var coursecount = 0;
                 for (var i in object.children) {
@@ -670,9 +676,14 @@ BRANCH.prototype = {
                 return true;
             }
             Y.log('AJAX loading complete but there were no children.', 'note', 'moodle-block_navigation');
-        } catch (ex) {
+        } catch (error) {
             // If we got here then there was an error parsing the result.
             Y.log('Error parsing AJAX response or adding branches to the navigation tree', 'error', 'moodle-block_navigation');
+            Y.use('moodle-core-notification-exception', function () {
+                return new M.core.exception(error).show();
+            });
+
+            return false;
         }
         // The branch is empty so class it accordingly
         this.node.replaceClass('branch', 'emptybranch');

lib/ajax/getsiteadminbranch.php

@@ -39,14 +39,24 @@ if ($branchtype !== navigation_node::TYPE_SITE_ADMIN) {
     die('Wrong node type passed.');
 }
 
+// Start capturing output in case of broken plugins.
+ob_start();
+
 $PAGE->set_context(context_system::instance());
 $PAGE->set_url('/lib/ajax/getsiteadminbranch.php', array('type'=>$branchtype));
 
 $sitenavigation = new settings_navigation_ajax($PAGE);
 
-// Set XML headers.
-header('Content-type: text/plain; charset=utf-8');
-// Convert and output the branch as XML.
+// Convert and output the branch as JSON.
 $converter = new navigation_json();
 $branch = $sitenavigation->get('root');
-echo $converter->convert($branch);
+
+$output = ob_get_contents();
+ob_end_clean();
+if ($CFG->debugdeveloper && !empty($output)) {
+    throw new coding_exception('Unexpected output whilst building the administration tree. ' .
+            'This could be caused by trailing whitespace. Output received: ' .
+            var_export($output, true));
+} else {
+    echo $converter->convert($branch);
+}