Implemented pluggable normalisers

packages/gatsby-source-wordpress/src/gatsby-node.js

@@ -1,6 +1,7 @@
 const fetch = require(`./fetch`)
 const normalize = require(`./normalize`)
 const Normalizer = require(`./normalizer`)
+const _ = require(`lodash`)
 
 const typePrefix = `wordpress__`
 const refactoredEntityTypes = {
@@ -77,13 +78,19 @@ exports.sourceNodes = async (
     .set(normalize.searchReplaceContentUrls, 130)
 
   for (let i = 0; i < plugins.length; i++) {
-      const requiredPlugin = require(plugins[i].resolve)
-      normalizer = requiredPlugin.normalize(normalizer)
+    var requiredPlugin = require(plugins[i].resolve)
+
+    if (_.isFunction(requiredPlugin.normalize)) {
+      var pluginNormalizer = requiredPlugin.normalize(normalizer)
+      if (pluginNormalizer instanceof Normalizer) {
+        normalizer = pluginNormalizer
+      }
+    }
+
   }
 
   entities = await normalizer.normalize()
 
-  // creates nodes for each entry
   normalize.createNodesFromEntities({ entities, createNode })
 
   return

packages/gatsby-source-wordpress/src/normalizer.js

@@ -1,38 +1,65 @@
+const _ = require(`lodash`)
 
 class Normalizer {
 
+    /**
+     * Normalizer Constructor
+     * 
+     * @param  {Array} entitys
+     * @param  {Object} args
+     * @return {Object} this
+     */
     constructor(entitys, args) {
         this.entitys = entitys
         this.args = args
         this.normalizers = []
+        this.queue = []
     }
 
+    /**
+     * Set Normalizers
+     * 
+     * @param {Function} normalizer
+     * @param {null|Number} priority
+     * @return {Object}
+     */
     set(normalizer, priority = null) {
-        // if the priority is null push last
-        this.normalizers.push({
+        let property = priority === null ? `queue` : `normalizers`
+
+        this[property].push({
             normalizer,
             priority,
         })
 
         return this
     }
 
+    /**
+     * Normalize the entities
+     * 
+     * @return {Array}
+     */
     async normalize() {
-        let ordered = this.normalizers.sort((a, b) => a.priority - b.priority)
-
-        for (let i = 0; i < ordered.length; i++) {
-            var normalizedEntities = await ordered[i].normalizer(this.entitys, this.args)
-
-            if (typeof normalizedEntities !== `object`) {
-                continue
-            }
-
-            this.entitys = normalizedEntities
+        var normalizers = this.getNormalizers()
+        for (let i = 0; i < normalizers.length; i++) {
+            this.entitys = await normalizers[i].normalizer(this.entitys, this.args)
         }
 
         return this.entitys
     }
 
+    /**
+     * Concat the queue and prioritised normalizers
+     * 
+     * @return {Array}
+     */
+    getNormalizers() {
+        return _.concat(
+            this.normalizers.sort((a, b) => a.priority - b.priority),
+            this.queue
+        )
+    }
+
 }
 
 module.exports = Normalizer