Breadcrumbs SEO microdata includes invalid values for IDs if no href

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I’m using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

If a breadcrumb item (such as a category item in the sidebar) has no link (and thus no href) the generated SEO microdata is invalid. Since the generator is designed to pick an href and use it as the id, it looks like if there’s no href to take it default to whatever text is visible inside the element.

So, if you have, e.g. a sidebar with nested items:

Then the generated breadcrumbs have no links associated to them. The generator takes, in this case "MCU Guides" as its ID, which is apparently invalid:

In these cases, I think it would be appropriate to not add an ID property at all.

Reproducible demo

No response

Steps to reproduce

1. Add a nested sidebar to Docusaurus:

// E.g. in sidebar.js
module.exports = {
    docs: {
        "Some Category": {
            type: "category",
            label: "Some Label",
            items: [
                "some-category/actual-docs"
            ]
        }
    }
};

1. Run the Google rich results validator on the resulting page: https://search.google.com/test/rich-results

Confirm that the ID of the SEO microdata is Some Category, which is invalid.

Expected behavior

No ID gets added in the generated SEO microdata for breadcrumbs without an href.

Actual behavior

An invalid ID gets added, using the text value from the category breadcrumb, because there’s no href to take from.

Your environment

• Public source code: https://github.com/memfault/memfault-docs/blob/main/sidebars.js
• Public site URL: https://docs.memfault.com/docs/mcu/event-serialization-overview/
• Docusaurus version used: 2.0.0-beta.18

Self-service

• I’d be willing to fix this bug myself.

[Josh-Cena]

No, not defaulting category indexes, because that doesn’t make much sense. But defaulting breadcrumb links is something we can do (i.e. even if there’s no category link, we can find a link, like the first doc). In fact, we already have such algorithm: if JS is disabled, you can still navigate through the categories, because each category will always have a link that’s clickable, just that it may be removed after React hydration.

[Josh-Cena]

If breadcrumb does not have link, we could remove the microdata?

I thought about that at the time I was implementing it, but I don’t like the idea. A breadcrumb item should be allowed without a link (at least the schema allows it, not to say it’s any good for SEO anyways)