Update fetchpriority to match final spec

[pmeenan]

Description

This updates the fetchpriority HTML attribute and priority fetch option to match the final spec.

Motivation

The Priority Hints spec was merged into the HTML and fetch specs, obsoleting the original spec.

Additional details

Here is the HTML spec PR and the Fetch spec PR.

Summarized changes:

• The iFrame element no longer supports the fetchPriority attribute (was never implemented anywhere).
• The img, link and script elements point to the appropriate HTML spec pages.
• The priority option as part of creating a fetch request was updated.
• A stray reference to the old importance attribute was updated.

One thing that I couldn't quite make out is that the Fetch spec accounts for a Request object but also a RequestInit object that is used when constructing a request. The priority is not readable from Request, it is only settable at construct time. I removed it from the JSON and Request interfaces and added it to the main fetch page where it talks about constructor options but the RequestInit itself doesn't appear to be directly documented.

Related issues and pull requests

Fixes #24519

[github-actions]

Preview URLs (9 pages)

• /en-US/docs/Learn/Performance/Multimedia
• /en-US/docs/Web/API/Fetch_API/Using_Fetch
• /en-US/docs/Web/API/HTMLLinkElement/fetchPriority
• /en-US/docs/Web/API/HTMLLinkElement
• /en-US/docs/Web/API/Request/Request
• /en-US/docs/Web/API/Request
• /en-US/docs/Web/API/fetch
• /en-US/docs/Web/HTML/Element/iframe
• /en-US/docs/Web/HTML/Element/link

Flaws (12)

Note! 6 documents with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/Web/API/Request/Request
Title: Request()
Flaw count: 1

• broken_links:
  • Can't resolve /en-US/docs/Web/API/abortsignal

---

URL: /en-US/docs/Web/API/HTMLLinkElement
Title: HTMLLinkElement
Flaw count: 10

• macros:
  • /en-US/docs/Web/API/HTMLLinkElement/crossOrigin does not exist
  • /en-US/docs/Web/API/HTMLLinkElement/disabled does not exist
  • /en-US/docs/Web/API/HTMLLinkElement/href does not exist
  • /en-US/docs/Web/API/HTMLLinkElement/hreflang does not exist
  • /en-US/docs/Web/API/HTMLLinkElement/media does not exist
  • and 5 more flaws omitted

---

URL: /en-US/docs/Web/HTML/Element/iframe
Title: <iframe>: The Inline Frame element
Flaw count: 1

• broken_links:
  • Can't resolve /en-US/docs/Learn/Common_questions/What_is_a_URL

External URLs (2)

URL: /en-US/docs/Web/HTML/Element/iframe
Title: <iframe>: The Inline Frame element

• https://example.org (1 time)
• https://www.w3.org/TR/html-aria/ (1 time)

(comment last updated: 2023-02-18 15:28:43)

[wbamberg]

Thanks for this update, @pmeenan !

One thing that I couldn't quite make out is that the Fetch spec accounts for a Request object but also a RequestInit object that is used when constructing a request. The priority is not readable from Request, it is only settable at construct time. I removed it from the JSON and Request interfaces and added it to the main fetch page where it talks about constructor options but the RequestInit itself doesn't appear to be directly documented.

Yes, on MDN we usually don't document dictionaries like this as standalone objects/pages. We just document them inline in the place they are used, so here it looks like we should update the options parameter to the Request() constructor: https://developer.mozilla.org/en-US/docs/Web/API/Request/Request#options .

[pmeenan]

@wbamberg Thanks. I updated the Request() page so the options include the same priority change that was added to the fetch page.

I also put the experimental flag back since neither WebKit nor Gecko's implementations have made it to a stable browser yet. I'll submit another PR once that happens to include the version info and remove the flag.

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[pmeenan]

Sorry, rebase went horribly wrong - will submit a new, clean PR

[pmeenan]

Clean PR created: #24595