Extend document.open/write to non-active documents #2827

dvoytenko · 2017-07-11T06:04:31Z

As it stands, the spec defines that document.open and document.write should be a no-op for a non-active document. See http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#dom-document-write:

If document is not an active document, then return.

However, document.open/write is a convenient (and essentially the only) way to incrementally stream-parse DOM. For instance:

var parser = document.implementation.createHTMLDocument('');
parser.open();
parser.write('<html><body>...');
parser.close();

Despite the spec, all major browsers except Firefox support this. See https://bugzilla.mozilla.org/show_bug.cgi?id=867102

Alternatives to using this API would be either parse the whole DOM in one go using DOMParser or, what most often done on Firefox as a workaround, to parse via a hidden iframe. IMHO both alternatives are significantly worse than expanding the spec to what most of browsers already do.

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bzbarsky · 2017-07-11T06:25:50Z

Need tests to see what various browsers do for non-active documents in browsing contexts, at the very least.

Also, need to figure out what open should really do for documents with no window.

annevk · 2017-07-11T11:30:35Z

cc @whatwg/html-parser

RReverser · 2017-07-11T12:35:46Z

Also, need to figure out what open should really do for documents with no window.

Not sure how window matters for document.open?

inikulin · 2017-07-11T12:52:15Z

I'm not a big fan of this streaming parsing hack via document.write. Maybe we can work on implementing streaming API for DOMParser instead?

jdm · 2017-07-11T13:41:49Z

@RReverser steps 15-19 of https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#document-open-steps.

RReverser · 2017-07-11T13:54:26Z

@jdm Ah. It creates a new Window object, so steps should be same. Doesn't really matter that there is no "physical" window in UI.

wanderview · 2017-07-11T13:59:48Z

Note, the spec creates a new window global, but not all browsers implement that. We implement it in firefox, but I believe other browsers just reset some state on the current global.

annevk · 2017-07-11T14:00:45Z

Yeah, that is #1698.

bzbarsky · 2017-07-11T14:30:05Z

It creates a new Window object, so steps should be same.

Almost certainly not, for documents that don't have a Window to start with. Like I said, needs some careful thought.

But yes, it really would be good to have a sane streaming parsing API; people keep asking for that. That might be somewhat orthogonal to whether we support open/write on non-browser-context docs for compat reasons.

domenic · 2017-07-11T15:43:41Z

I'd strongly prefer if other browsers fixed their document.open/document.write, and we created a reasonable streaming parser API instead.

dvoytenko · 2017-07-11T19:58:17Z

@domenic For continuity, I'd prefer the other browsers to keep the existing document.open/write until they make the streaming API available.

That being said, I suspect it might be hard to get the consensus on what streaming DOM parsing would be and document.open/write are already there and I just don't see a huge conceptual difference between current per-spec document.open/write and extending it to detached docs like most of browsers do. I'm concerned that a straightforward and tangible improvement would be swallowed by a much bigger spec work.

RByers · 2017-07-11T20:39:42Z

Screenshots confirming @dvoytenko's claim that all major browsers except Firefox support this based on a trivial test.

Filed a chromium bug to track the deviation from the spec here. I don't see an existing UseCounter quantifying the web compat risk of trying to change this, but with (at least) AMP depending on this behavior any measure is likely to be substantial.

Since 3 browsers already implement this and there's some not-easily-quantified compat risk to changing it, perhaps we should update the spec / tests to match reality in parallel to whatever people want to do with a parser API? If we want more web compat data confirming this isn't easy to break we could add a UseCounter to chromium then check the HTTP Archive for (non-AMP) sites hitting it during page load, but that'll take a few months to get results for.

dvoytenko · 2017-08-28T18:21:52Z

Hi All! Wanted to circle back and follow up on this issue. Is it possible to achieve a consensus and standardize this behavior? Or create an alternative?

domenic · 2017-08-28T18:28:46Z

I don't have the resources at the moment to work on either a good streaming parser API or an interoperable spec and comprehensive set of tests that covers all the permutations @bzbarsky mentions (plus the known interop issue of #1698 that may block this one).

dominiccooney · 2017-09-01T05:43:38Z

I filed Issue 2993 to take a stab at what asynchronous parsing might look like.

There is no longer anything fundamental that prevents document.open() from being useful on non-active documents. This also aligns with Chrome, Edge, and Safari. In fact, several projects like AMP already utilize this property as a streaming HTML parser to desirable effects. Fixes whatwg#2827. Tests: web-platform-tests/wpt#12636 Tests: …

There is no longer anything fundamental that prevents document.open() from being useful on non-active documents. This also aligns with Chrome, Edge, and Safari. In fact, some developers already utilize this property as a streaming HTML parser to desirable effect (see #2827). Additionally, use a more appropriate guard for erasing event listeners and handlers on the Window object, as revealed by the tests. Fixes #2827. Tests: web-platform-tests/wpt#12636 Tests: web-platform-tests/wpt#12770

There is no longer anything fundamental that prevents document.open() from being useful on non-active documents. This also aligns with Chrome, Edge, and Safari. In fact, some developers already utilize this property as a streaming HTML parser to desirable effect (see whatwg#2827). Additionally, use a more appropriate guard for erasing event listeners and handlers on the Window object, as revealed by the tests. Fixes whatwg#2827. Tests: web-platform-tests/wpt#12636 Tests: web-platform-tests/wpt#12770

annevk added the topic: parser label Jul 11, 2017

domenic added the interop Implementations are not interoperable with each other label Jul 13, 2017

dominiccooney mentioned this issue Sep 1, 2017

Add a "modern" parsing API #2993

Closed

TimothyGu added topic: document.open() and removed topic: document.open() labels Jun 26, 2018

domenic mentioned this issue Jul 9, 2018

Audit "active document" checks #3812

Closed

TimothyGu mentioned this issue Jul 12, 2018

Tracking issue for document.open() overhaul #3818

Closed

19 tasks

TimothyGu mentioned this issue Aug 30, 2018

Allow document.open() to be called on non-active documents #3977

Merged

domenic closed this as completed in #3977 Sep 4, 2018

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Extend document.open/write to non-active documents #2827

Extend document.open/write to non-active documents #2827

dvoytenko commented Jul 11, 2017

bzbarsky commented Jul 11, 2017

annevk commented Jul 11, 2017

RReverser commented Jul 11, 2017

inikulin commented Jul 11, 2017

jdm commented Jul 11, 2017

RReverser commented Jul 11, 2017

wanderview commented Jul 11, 2017

annevk commented Jul 11, 2017

bzbarsky commented Jul 11, 2017

domenic commented Jul 11, 2017

dvoytenko commented Jul 11, 2017

RByers commented Jul 11, 2017 •

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dvoytenko commented Aug 28, 2017

domenic commented Aug 28, 2017

dominiccooney commented Sep 1, 2017 •

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Extend document.open/write to non-active documents #2827

Extend document.open/write to non-active documents #2827

Comments

dvoytenko commented Jul 11, 2017

bzbarsky commented Jul 11, 2017

annevk commented Jul 11, 2017

RReverser commented Jul 11, 2017

inikulin commented Jul 11, 2017

jdm commented Jul 11, 2017

RReverser commented Jul 11, 2017

wanderview commented Jul 11, 2017

annevk commented Jul 11, 2017

bzbarsky commented Jul 11, 2017

domenic commented Jul 11, 2017

dvoytenko commented Jul 11, 2017

RByers commented Jul 11, 2017 • edited Loading

dvoytenko commented Aug 28, 2017

domenic commented Aug 28, 2017

dominiccooney commented Sep 1, 2017 • edited Loading

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dominiccooney commented Sep 1, 2017 •

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