How to return 404 page in next.js if data is not found in Wordpress admin?

Question

I have the following json data

[
    {
        "taxonomy_slug": "product_cat",
        "taxonomy_name": "Categories",
        "frontend_slug": "product-category"
    },
    {
        "taxonomy_slug": "product_tag",
        "taxonomy_name": "Tags",
        "frontend_slug": "product-tag"
    },
    {
        "taxonomy_slug": "gift_box_size",
        "taxonomy_name": "Gift Box Sizes",
        "frontend_slug": "gift_box_size"
    },
    {
        "taxonomy_slug": "product-type",
        "taxonomy_name": "Type",
        "frontend_slug": "product-type"
    }
]

So for each taxonomy front-end slug, I want to generate a page for each taxonomy.

the URLs I want to generate are as follows

product-category/{category_item_slug} product-tag/{tag_item_slug} gift_box_size/{gift_box_size_item_slug} product-type/{product-type_item_slug}

Now each taxonomy has its own list of items and if it doesn't exist in the Wordpress admin, I want to return 404 page not found.

I have the following file/folder structure

|-> pages
  |-> [taxonomy-frontend-slug]
    |-> [taxonomy-item-slug].js

[taxonomy-item-slug].js file

import { useRouter } from 'next/router'
import productTaxonomy from '@gb-data/productTaxonomy.json'
export async function getStaticPaths() {

    const paths = productTaxonomy.map((taxonomyData) => {
        return {
            params: { "taxonomy-frontend-slug": `/${taxonomyData.frontend_slug}` }
        }
    })

    console.log('getStaticPaths', paths)
    return {
        paths: paths,
        fallback: false,
    }
}

export async function getStaticProps(context) {
    console.log('getStaticProps context', context)
    return {
        props: {}
    }
}


export default function TaxonomyItemPage() {
    const router = useRouter()
    console.log('router.query', router.query);

    return (
        <div>
            TaxonomyItemPage
        </div>
    )
}

Answer 1

I see 2 options:

1. Do not return non-existent taxonomies from getStaticPaths . With fallback: false , users will get 404 for any paths not returned by this function.

Something like that should do the trick:

export async function getStaticPaths() {
    const taxonomies = await getListOfTaxonomiesFromWordpress();
    const paths = taxonomies.map((taxonomyData) => {
        return {
            params: { "taxonomy-frontend-slug": taxonomyData.frontend_slug }
        }
    })

    return {
        paths: paths,
        fallback: false,
    }
}

2. When loading static props for a path (provided you don't have getStaticPaths function like in 1 ), return the following from getStaticProps if data is not available in Wordpress in order to get 404:

return {
  notFound: true
};

So try the following:

export async function getStaticProps({ params }) {
    const taxonomyData = await getTaxonomyDataBySlugFromWordpress(params['taxonomy-frontend-slug']);
    if (taxonomyData) {
      return {
          props: { taxonomyData }
      }
    }
    
    return {
        notFound: true
    }
}