[gatsby-source-wordpress] Treat wp settings as a known type for inclu…

…sion (#5708)

* Append wordpress_id to wp settings to prevent exclusion

Signed-off-by: Adam Mould <adamwmould@gmail.com>

* Treat wp settings as a known type

Signed-off-by: Adam Mould <adamwmould@gmail.com>

* Comments to explain normalize functions

Signed-off-by: Adam Mould <adamwmould@gmail.com>

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

@@ -137,12 +137,20 @@ exports.liftRenderedField = entities =>
   })
 
 // Exclude entities of unknown shape
+// Assume all entities contain a wordpress_id, except for whitelisted type wp_settings
 exports.excludeUnknownEntities = entities =>
-  entities.filter(e => e.wordpress_id) // Excluding entities without ID
+  entities.filter(e => e.wordpress_id || e.__type === `wordpress__wp_settings`) // Excluding entities without ID, or WP Settings
 
+// Create node ID from known entities
+// excludeUnknownEntities whitelisted types don't contain a wordpress_id
+// we create the node ID based upon type if the wordpress_id doesn't exist
 exports.createGatsbyIds = (createNodeId, entities) =>
   entities.map(e => {
-    e.id = createNodeId(`${e.__type}-${e.wordpress_id.toString()}`)
+    if (e.wordpress_id) {
+      e.id = createNodeId(`${e.__type}-${e.wordpress_id.toString()}`)
+    } else {
+      e.id = createNodeId(e.__type)
+    }
     return e
   })