Difficult for authors to embed image media with empty alt text.

Here's the brain-dump from a Slack conversation today. Use this to update the issue summary.

andrewmacpherson 2:50 PM
I think I've run into a restriction with embedded media filter (or widget, not sure which exactly). I can't figure out how to embed an image without a text alternative. It's like we are forcing authors to use the alt text from the media entity, or provide an instance-specific override. But for embedded media, it should be possible to embed an image with alt="". Am I missing some step?

I can achieve it if I jump through some hoops.
1. Embed an image media-item, add "foo" as the alt text.
2. Show source in CKEditor. The markup is: <drupal-media alt="foo" data-align="center" data-caption=" " data-entity-type="media" data-entity-uuid="78c82be9-06d9-46fb-871b-cbf03d47446b"></drupal-media>
3. Edit the markup to alt="", save it the node.Success, but I had to edit the source.

Luke Leber:speech_balloon: 2:56 PM
Is your media system set up to require the alt attribute?

andrewmacpherson 2:56 PM
In which config, exactly?

phenaproxima (he/him) 2:56 PM
@andrewmacpherson The embedded media dialog should allow you to set "" as the value in the alt text box, which will make it empty.

Luke Leber:speech_balloon: 2:56 PM
I believe it's in the media source image file field config on the media entity? (edited) 

phenaproxima (he/him) 2:57 PM
@wimleers (he/him) and @oknate can verify this

andrewmacpherson 2:57 PM
@phenaproxima (he/him) that's not discoverable.

phenaproxima (he/him) 2:57 PM
One sec

oknate 2:58 PM
you have to set it to two double quotes encoded

phenaproxima (he/him) 2:58 PM
@andrewmacpherson Hah — it actually will show up if you try to submit it with empty alt text.
@andrewmacpherson See EditorMediaDialog.php, line 140.
@andrewmacpherson It’s worth opening a quick issue to add it to the #description too.
It’s discoverable…by accident =P
I knew we had it somewhere in the dialog, I remember seeing it, but it’s a #required_error of the alt text field.
So…dang
That was dumb =P

oknate 2:59 PM
If you use the dialog and set it to “” it works too
not an empty string, but literally, two double quotes

phenaproxima (he/him) 3:00 PM
@oknate Right, but that’s not documented in the dialog unless you try to submit with no value in the alt field.

andrewmacpherson 3:00 PM
Another WTF. If I return to the content later, because I want to change the alignment, say, I open the media embed widget to change the alignment, it also restores the default alt text associated with the media entity. That's not what I wanted to edit. It seems that the editor widget enforces a value for the alt text.

oknate 3:00 PM
that’s if you set alt=‘’ (an empty string)
it will inherit the default
to set it to blank i.e. an alt tag without a value, it needs to be two double quotes (edited) 
phenaproxima (he/him) 3:01 PM
Right, the difference here is between alt="" and alt="&quot;&quot;", effectively

oknate 3:01 PM
yes

phenaproxima (he/him) 3:01 PM
The former will restore default alt text. The latter will remove the alt attribute from the embed.

oknate 3:01 PM
not exactly, we never remove the alt, for accessibility reasons (edited) 

phenaproxima (he/him) 3:01 PM
Sorry, it will set alt=""

oknate 3:01 PM
but it will set it to no value
<img alt />

phenaproxima (he/him) 3:01 PM
Right.
It will set that on the rendered media.
But the embed code will retain alt="&quot;&quot;", which should carry into the dialog too.

oknate 3:02 PM
it does

phenaproxima (he/him) 3:02 PM
@andrewmacpherson Clearly we have done a poor job of making this, well, clear in the UI. Definitely warrants an issue IMHO

andrewmacpherson 3:04 PM
The thing is, for ATAG, there should be a way for the user to get the default alt text. As in, they had an instance override, but now they want to go back to the default alt text from the media entity.
So there are some overlapping needs here.

oknate 3:04 PM
they just need to leave it blank in the dialog
the original alt text will be restored

andrewmacpherson 3:04 PM
yeah, but blank ought to mean alt=""

phenaproxima (he/him) 3:05 PM
In our implementation, "" means alt=""
And…this is how the image plugin already works

andrewmacpherson 3:05 PM
So there's some conflated behaviour here. Both operation (defaualt alt text, or empty alt text) are valid needs.

phenaproxima (he/him) 3:05 PM
We just copied an existing pattern in core
I am +1 for opening an issue to fix it in both places.

andrewmacpherson 3:07 PM
image widget is has different requirements though. It isn't from a media library, so it doesn't have default alt to override/restore.

phenaproxima (he/him) 3:08 PM
Right, but it copies the same general form patterns. For media, this is why we use a placeholder on the alt text field.
So that’s more “obvious”, at least in theory, that no value == default alt text

andrewmacpherson 3:15 PM
I'll file an issue. Anyone mind if I grab this conversation as the initial issue summary/brain-dump?

phenaproxima (he/him) 3:15 PM
@andrewmacpherson Please do.

wimleers (he/him) 3:17 PM
@phenaproxima (he/him) I actually pointed that out in a review that we broke the decorative image alt text discoverability  when we did the “inherit from media entity” thing
We copied the pattern from EditorImageDialog and that was fine. But then we added the automatic inheritance, and then we broke it.
We should keep the pattern, it was vetted years ago by a11y maintainers.
But we need to figure out how to combine that with the inheritance need.

phenaproxima (he/him) 3:20 PM
Do we classify this as a usability/AX issue, or an a11y issue? I would think the former, because there are workarounds. It’s just that the UX kinda sucks
Unless I am not understanding this

andrewmacpherson 3:25 PM
AX. I'm coming at this from ATAG part B: "Support the production of accessible content". The UI doesn't support authors who know that alt="" is what they need.

phenaproxima (he/him) 3:25 PM
+1. Please link me to the issue, @andrewmacpherson, when you have it. I’m going to add it to the roadmap as being in need of triage.

There are several open issues relating to the author tools for alt text, each trying different things. There are too many, and I fear we'll end up with something messy.

So I'd like to gather them under one parent, and take stock. Some will indeed turn out to be duplicates. Some others should be marked won't-fix, because they undermine the content model for existing sites.