fix(gatsby): node manifests v2 inc builds (#34086)

* only log error id array if there are errors

* fix createNodeManifest 2.0 for inc-builds

packages/gatsby/src/utils/node-manifest.ts

@@ -392,7 +392,7 @@ export async function processNodeManifests(): Promise<Map<
   )
 
   reporter.info(
-    (!verboseLogs
+    (!verboseLogs && listOfUniqueErrorIds.size > 0
       ? `unstable_createNodeManifest produced warnings [${[
           ...listOfUniqueErrorIds,
         ].join(`, `)}]. `

packages/gatsby/src/utils/page-data.ts

@@ -174,9 +174,14 @@ export async function flush(parentSpan?: Span): Promise<void> {
   )
   writePageDataActivity.start()
 
-  // we process node manifests in this location because we need to add the manifestId to the page data.
-  // We use this manifestId to determine if the page data is up to date when routing. Here we create a map of "pagePath": "manifestId" while processing and writing node manifest files.
-  const nodeManifestPagePathMap = await processNodeManifests()
+  let nodeManifestPagePathMap
+
+  if (pagePaths.size > 0) {
+    // we process node manifests in this location because we need to add the manifestId to the page data.
+    // We use this manifestId to determine if the page data is up to date when routing. Here we create a map of "pagePath": "manifestId" while processing and writing node manifest files.
+    // We only do this when there are pending page-data writes because otherwise we could flush pending createNodeManifest calls before page-data.json files are written. Which means those page-data files wouldn't have the corresponding manifest id's written to them.
+    nodeManifestPagePathMap = await processNodeManifests()
+  }
 
   const flushQueue = fastq(async (pagePath, cb) => {
     const page = pages.get(pagePath)