I've run a rough HTTP archive query on it, testing all HTTP responses last month (666 million): getComputedStyle with an argument that doesn't begin with "::" is called in 0.45% of pages, out of which 55% is ":before", 28% is after, and the vast majority of the rest are invalid pseudo-element names (e.g. "height" or "display"). There were extremely rare cases that would be affected: getComputedStyle(element, ":placeholder") or getComputedStyle(element, ":marker"), about 0.00001% of requests (34 out of 666 million). I'm running a more refined version of the query but I doubt I'll get significantly different results.
So I'd perhaps classify backwards compatibility as low-risk? On Mon, Mar 11, 2024 at 9:32 AM Noam Rosenthal <nrosent...@chromium.org> wrote: > > > On Mon, Mar 11, 2024 at 5:57 AM Domenic Denicola <dome...@chromium.org> > wrote: > >> Thanks Dan for raising the compat concerns here. It seems like a mistake >> that the original Intent says "None" for that, >> > Good point, I updated it. > > > >> and I think we need to get that section of the Chrome Status entry >> fleshed out before considering approvals here. >> > >> What I'm hearing so far is that we think the compat risks might be small >> because Gecko and WebKit are already using strict parsing. That's >> something, but can we do better? For example: >> >> - Is there any upper bound on the potential number of broken page >> views? Ideally we'd have a use counter for how many times the lenient >> parsing is triggered, but for an upper bound even just a use counter for >> how many times these arguments are supplied to getComputedStyle()/new >> KeyframeEffect() would help. >> - Can we do an HTTP archive analysis of some sort? >> >> Will do both and come back with results. > >> >> On Sun, Mar 10, 2024 at 5:55 PM Noam Rosenthal <nrosent...@chromium.org> >> wrote: >> >>> >>> >>> On Fri, Mar 8, 2024 at 11:56 PM 'Dan Clark' via blink-dev < >>> blink-dev@chromium.org> wrote: >>> >>>> Am I correct in understanding that Gecko already mostly matches the >>>> behavior in the spec? I see that Firefox also fails most of the WPTs at >>>> https://wpt.fyi/results/css/cssom/getComputedStyle-pseudo-with-argument.html?label=master&label=experimental&aligned, >>>> but I guess that's because they haven't shipped ::highlight() pseudos. >>> >>> Correct, it's because of ::highlight. It passes most of the tests in >>> https://wpt.fyi/results/css/cssom/getComputedStyle-pseudo.html?label=master&label=experimental&aligned >>> . >>> >>> >>>> How are you thinking about the compatibility risk? If we're making the >>>> parsing stricter in certain ways, presumably sites depending on that >>>> behavior could break. Omitting the ":" seems like it could be a >>>> particularly easy mistake to make. On the other hand the fact that WebKit >>>> (and I guess Gecko) already did it is an encouraging signal. >>>> >>> >>> Correct. Also, intending to keep current behavior for old pseudos that >>> support single-colon in regular CSS (before, after, first-line, >>> first-letter). If there are other exceptions with a lot of existing code we >>> can consider adding them here. >>> >>> The way I'm thinking about this from a compat perspective is that if we >>> keep supporting single-colon/no-colon for all pseudos, there would be more >>> non-spec-compliant code written with those, that would seem to work in >>> chrome while developing and then not work in other browsers. So aligning >>> with the spec now is hopefully cleaner. >>> >>> However, if there are reasons to keep some of the parsing more lenient >>> here I'm happy to hear and find the best solution for the web platform. >>> >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "blink-dev" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to blink-dev+unsubscr...@chromium.org. >>> To view this discussion on the web visit >>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJn%3DMYbLLqWEjSNYnt6Pw%2BcV75%3DryQ%3DbsDM%3DAXtktKW6C__kkQ%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJn%3DMYbLLqWEjSNYnt6Pw%2BcV75%3DryQ%3DbsDM%3DAXtktKW6C__kkQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJn%3DMYaL0OCQf6f_Tu3v_Jv1Rg-zMv1dqM%2BcppW9KFcGAoD5_A%40mail.gmail.com.
