"fallback base URL" algorithm seems wrong for popups?

[domenic]

https://html.spec.whatwg.org/#fallback-base-url

If document's URL is about:blank, and document's browsing context's creator base URL is non-null, then return that creator base URL.

From what I can tell, popups from window.open() will have a creator base URL.

But, if I do window.open() (no args) or window.open("about:blank"), and then check the opened window in the dev console, I get:

document.documentURI === "about:blank";
document.baseURI === "about:blank"; // *not* the creator base URL

Am I missing something, or is this fairly basic part of the spec wrong?

[annevk]

WebKit does inherit here.

cc @cdumez

[domfarolino]

Yeah Chrome doesn't seem to match the spec here I guess. Maybe we should file a Chome bug?

[annevk]

I think WebKit is the odd-one-out and inheriting isn't necessarily better. I guess it depends on what else gets inherited and what would make sense from a policy container point-of-view.

[zcorpan]

Demos: window.open(), window.open('about:blank')

Test	Firefox	Safari	Chrome
open(): documentURI	about:blank	about:blank	about:blank
open(): baseURI	about:blank	opener's url	opener's url
open('about:blank'): documentURI	about:blank	about:blank	about:blank
open('about:blank'): baseURI	opener's url	opener's url	opener's url

My result is different from what @domenic said in OP for Chrome.

Tested with

• Firefox 115.0a1 (2023-05-22) (64-bit)
• Safari TP Release 168 (Safari 16.4, WebKit 18616.1.10.2)
• Chrome 115.0.5776.0 (Official Build) canary (arm64)

[domenic]

I've found a bit more background on this. @wjmaclean has been looking into about:blank URL inheritance, mostly for iframes, but he also plans to work on it for popups. See this Chromium doc. This is mostly captured in #421; in particular see my summary in #421 (comment).

This might also explain why Simon and I saw different results, if Simon was testing with experimental web platform features on in his Chrome Canary, or if these changes are rolling out to 50% or similar (which is pretty common on Canary channel).

It seems like there is a separate issue here where open() and open("about:blank") are not treated the same in Firefox.

I will file a Chromium issue to help @wjmaclean remember to write web platform tests for the popup cases in addition to the iframe cases which he's already written tests for.

With this in mind, let me close this issue and re-title #421 to also mention popups.