fix: improve cache handling and error recovery

[sy-records]

Summary

Related issue, if any:

Close #2741

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

For any code change,

• Related documentation has been updated, if needed
• Related tests have been added or updated, if needed

Does this PR introduce a breaking change?

• Yes
• No

Tested in the following browsers:

• Chrome
• Firefox
• Safari
• Edge

[vercel]

@sy-records is attempting to deploy a commit to the Docsify Team on Vercel.

A member of the Team first needs to authorize it.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
docsify-preview	Ready	Preview, Comment	Jun 11, 2026 5:43am

[Copilot]

Pull request overview

This PR fixes two rendering/cache edge cases in Docsify: memoization that previously failed to cache falsy/undefined results, and embed :include rendering that could stall or error when an embed fetch fails. It also adds coverage to prevent regressions.

Changes:

• Fix cached(fn) to memoize falsy and undefined return values correctly.
• Ensure failed embed fetches don’t block prerendering, and avoid accessing embedToken.links when no embed token was produced.
• Add unit/integration tests for the above behaviors.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
test/unit/core-util.test.js	Adds unit tests validating cached() memoizes falsy and undefined values.
test/integration/embed.test.js	Adds an integration test ensuring a failed :include fetch does not block rendering.
src/core/util/core.js	Updates cached() implementation to use key existence checks rather than truthiness.
src/core/render/embed.js	Adds embed fetch error handling and adjusts prerender logic to tolerate missing embed tokens.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

[paulhibbitts]

Hi @sy-records , thanks very much for taking this on! I was unable to test this issue on Codesandbox (maybe file error checking?) so I created a repo on GitHub at https://github.com/paulhibbitts/docsify-v5-failed-embeds

Using the current RC and an unavailable embed, the loading of the site clearly failed:

While using the PR Preview build the site was able to load successfully!
https://paulhibbitts.github.io/docsify-v5-failed-embeds/#/

So testing results are looking good for me.🙂