fix(gatsby-source-wordpress): invalidate less queries during previews

packages/gatsby-source-wordpress/src/steps/source-nodes/update-nodes/wp-actions/update.js

@@ -41,7 +41,7 @@ export const fetchAndCreateSingleNode = async ({
   const query = getNodeQuery()
 
   const {
-    helpers: { reporter },
+    helpers: { reporter, getNode },
     pluginOptions,
   } = getGatsbyApi()
 
@@ -71,7 +71,7 @@ export const fetchAndCreateSingleNode = async ({
     errorContext: `Error occurred while updating a single "${singleName}" node.`,
   })
 
-  const remoteNode = data[singleName]
+  let remoteNode = data[singleName]
 
   if (!data || !remoteNode) {
     reporter.warn(
@@ -89,6 +89,30 @@ export const fetchAndCreateSingleNode = async ({
     id,
   })
 
+  if (isPreview) {
+    const existingNode = getNode(id)
+
+    /**
+     * For Preview, revisions of a node type can have data that updates unecessarily
+     * This code block fixes that. The result being that less queries
+     * are invalidated in Gatsby. For example if you have a query where you're getting the latest published post using the date field, that should be static but each preview updates the date field on the node being previewed (because the revision has a new date). So if we prevent the following fields from changing, this will be less problematic.
+     */
+    if (existingNode) {
+      remoteNode = {
+        ...remoteNode,
+        databaseId: existingNode.databaseId,
+        date: existingNode.date,
+        dateGmt: existingNode.dateGmt,
+        slug: existingNode.slug,
+        guid: existingNode.guid,
+        id: existingNode.id,
+        link: existingNode.link,
+        uri: existingNode.uri,
+        status: existingNode.status,
+      }
+    }
+  }
+
   data[singleName] = remoteNode
 
   const { additionalNodeIds, node } = await createSingleNode({