feat(gatsby-source-wordpress): Log when nodes are duplicates (#29941)

packages/gatsby-source-wordpress/src/steps/source-nodes/fetch-nodes/fetch-nodes-paginated.js

@@ -1,5 +1,6 @@
 import fetchGraphql from "~/utils/fetch-graphql"
 import store from "~/store"
+import { formatLogMessage } from "../../../utils/format-log-message"
 
 export const normalizeNode = ({ node, nodeTypeName }) => {
   const normalizedNodeTypeName = node.__typename || nodeTypeName
@@ -11,6 +12,13 @@ export const normalizeNode = ({ node, nodeTypeName }) => {
   return node
 }
 
+// this is used to determine wether we've already seen an id
+// for cold builds.
+// the reason we want to do this is to detect if we create 2 nodes with the same id
+// if we do there will be less nodes in Gatsby than in WP and users will be confused.
+const idSet = new Set()
+let hasLoggedDuplicateMessage = false
+
 /**
  * paginatedWpNodeFetch
  *
@@ -85,6 +93,30 @@ const paginatedWpNodeFetch = async ({
 
   if (nodes && nodes.length) {
     nodes.forEach(node => {
+      const existingId = idSet.has(node.id)
+
+      if (existingId) {
+        const existingNode = allContentNodes.find(
+          innerNode => innerNode.id === node.id
+        )
+
+        if (!hasLoggedDuplicateMessage) {
+          hasLoggedDuplicateMessage = true
+          helpers.reporter.warn(
+            formatLogMessage(
+              `Found a duplicate ID in WordPress - this means you will have fewer nodes in Gatsby than in WordPress. This will need to be resolved in WP by identifying and fixing the underlying bug with your WP plugins or custom code.`
+            )
+          )
+        }
+        helpers.reporter.info(
+          formatLogMessage(
+            `#${node.databaseId} (${node?.uri}) is a duplicate of ${existingNode.databaseId} (${existingNode?.uri})`
+          )
+        )
+      } else {
+        idSet.add(node.id)
+      }
+
       node = normalizeNode({ node, nodeTypeName })
       allContentNodes.push(node)
     })