null or undefined metadata isnt ignored

Question

Hi when i export a metadata such as:export async function generateMetadata({
  params,
}: {
  params: {
    slug: string;
  };
}): Promise<Metadata> {
  const { data } = await query({params});
 
  return {
    title: data.title,
    description: data.description,
  };
}if data.title is null or undefined, I would expect the metadata of layout.tsx to be picked up, but it doesnt. any ideas?

joulev · Accepted Answer

this looks like a nextjs bug (or it could be an intended behaviour, then it would be a "feature"). in the source code, they just [check for available properties](https://github.com/vercel/next.js/blob/89e68377baf3ea6d2bf09e0ae694f57ec5c8ea93/packages/next/src/lib/metadata/resolve-metadata.ts#L166) without checking whether the values for those properties are falsy.i think what you should do in this case is to do something like this (yeah it's dirty, i know, but there isn't much else that can be done here)export async function generateMetadata({
  params,
}: {
  params: {
    slug: string;
  };
}): Promise<Metadata> {
  const { data } = await query({params});
 
  const metadata: Metadata = {
    title: data.title,
    description: data.description,
  };
  if (!data.title) delete metadata.title;
  if (!data.description) delete metadata.description;
  return metadata;
}i'll see if i can find time to file a PR to fix this "bug" in nextjs

null or undefined metadata isnt ignored

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