Extracted ordering into separate bookshelf plugin

refs #11729

- Having a plugin allows to reason about ordering better and gives way
to further extraction away form the core.
- Just like with filtering, ordering falls into similar category of having effect on knex'es query builder object extension through additional statements - ORDER BY in this case.
- Because there were bugs associated with use of permittedAttributes inside of `parseOrderOption` method, introduced separate `orderAttributes` function which returns only those fields which are orderable (https://github.com/TryGhost/Ghost/issues/11729#issuecomment-685740836)

core/server/models/base/index.js

@@ -43,6 +43,9 @@ ghostBookshelf.plugin(plugins.customQuery);
 // Load the Ghost filter plugin, which handles applying a 'filter' to findPage requests
 ghostBookshelf.plugin(plugins.filter);
 
+// Load the Ghost filter plugin, which handles applying a 'order' to findPage requests
+ghostBookshelf.plugin(plugins.order);
+
 // Load the Ghost search plugin, which handles applying a search query to findPage requests
 ghostBookshelf.plugin(plugins.search);
 
@@ -170,6 +173,11 @@ ghostBookshelf.Model = ghostBookshelf.Model.extend({
         return _.keys(schema.tables[this.tableName]);
     },
 
+    // Ghost ordering handling, allows to order by permitted attributes by default and can be overriden on specific model level
+    orderAttributes: function orderAttributes() {
+        return this.permittedAttributes();
+    },
+
     // When loading an instance, subclasses can specify default to fetch
     defaultColumnsToFetch: function defaultColumnsToFetch() {
         return [];
@@ -912,7 +920,7 @@ ghostBookshelf.Model = ghostBookshelf.Model.extend({
         }
 
         if (options.order) {
-            options.order = this.parseOrderOption(options.order, options.withRelated);
+            options.order = itemCollection.parseOrderOption(options.order, options.withRelated);
         } else if (options.autoOrder) {
             options.orderRaw = options.autoOrder;
         } else if (this.orderDefaultRaw) {
@@ -1165,43 +1173,6 @@ ghostBookshelf.Model = ghostBookshelf.Model.extend({
         return checkIfSlugExists(slug);
     },
 
-    parseOrderOption: function (order, withRelated) {
-        let permittedAttributes;
-        let result;
-        let rules;
-
-        permittedAttributes = this.prototype.permittedAttributes();
-        if (withRelated && withRelated.indexOf('count.posts') > -1) {
-            permittedAttributes.push('count.posts');
-        }
-        result = {};
-        rules = order.split(',');
-
-        _.each(rules, function (rule) {
-            let match;
-            let field;
-            let direction;
-
-            match = /^([a-z0-9_.]+)\s+(asc|desc)$/i.exec(rule.trim());
-
-            // invalid order syntax
-            if (!match) {
-                return;
-            }
-
-            field = match[1].toLowerCase();
-            direction = match[2].toUpperCase();
-
-            if (permittedAttributes.indexOf(field) === -1) {
-                return;
-            }
-
-            result[field] = direction;
-        });
-
-        return result;
-    },
-
     /**
      * If you want to fetch all data fast, i recommend using this function.
      * Bookshelf is just too slow, too much ORM overhead.

core/server/models/plugins/index.js

@@ -1,5 +1,6 @@
 module.exports = {
     filter: require('./filter'),
+    order: require('./order'),
     customQuery: require('./custom-query'),
     search: require('./search'),
     includeCount: require('./include-count'),

core/server/models/plugins/order.js

@@ -0,0 +1,46 @@
+const _ = require('lodash');
+
+const order = function order(Bookshelf) {
+    Bookshelf.Model = Bookshelf.Model.extend({
+        orderAttributes() {},
+
+        parseOrderOption: function (orderQueryString, withRelated) {
+            let orderAttributes;
+            let result;
+            let rules;
+
+            orderAttributes = this.orderAttributes();
+            if (withRelated && withRelated.indexOf('count.posts') > -1) {
+                orderAttributes.push('count.posts');
+            }
+            result = {};
+            rules = orderQueryString.split(',');
+
+            _.each(rules, function (rule) {
+                let match;
+                let field;
+                let direction;
+
+                match = /^([a-z0-9_.]+)\s+(asc|desc)$/i.exec(rule.trim());
+
+                // invalid order syntax
+                if (!match) {
+                    return;
+                }
+
+                field = match[1].toLowerCase();
+                direction = match[2].toUpperCase();
+
+                if (orderAttributes.indexOf(field) === -1) {
+                    return;
+                }
+
+                result[field] = direction;
+            });
+
+            return result;
+        }
+    });
+};
+
+module.exports = order;