Make block themes fully support HTML5 by default.

[costdev]

Follow-up to #54597.

This ticket proposes that block themes should fully support HTML5 by default.

Per ​add_theme_support() - HTML5, this includes:

• comment-list
• comment-form
• search-form
• gallery
• caption
• style
• script

Trac ticket: https://core.trac.wordpress.org/ticket/54731

[hellofromTonya]

Bringing the conversation here to this ticket to ensure context is here and those involved get props.

Thank you to @joyously who made the suggestion and pointed out that #54597 was too focused on only block content and not non-block content such as support for [gallery] and [caption] shortcodes.

I asked the question:

For block themes, do you think that Core should automatically default to HTML5 for all content (i.e. block and non-block content)? Or should the block theme itself set the non-block content theme supports (as non-block themes do)?

@joyously shared:

I think it would be good to force HTML5 for block themes, but that's just an opinion.

@costdev shared:

+1 That block themes should use HTML5 by default.

@audrasjb shared:

As far as I can tell, it would make sense if all block themes could only use and provide HTML5 markup. Block themes are a good way to drop non-HTML5 support in long term, if possible :)

[hellofromTonya]

What do I think?

I agree. This is a path forward by making new block themes HTML5 out-of-the-box within Core instead of within block themes.

Blocks include their own markup which is already HTML5.

This ticket adds theme supports so that non-block content (original content retained when upgrading to 5.9 and a block theme) is also HTML5.

Please note, non-block themes are not affected this ticket or change.

[hellofromTonya]

Follow-up to:

• #23850 [24417] which added 'search-form'. ''comment-form'', and ''comment-list' HTML5 theme supports.
• #26697 [27302] which added 'gallery' HTML5 theme support.
• #31053 [34261] which added 'caption' HTML5 theme support and markup to img_caption_shortcode().

[hellofromTonya]

@noisysocks @Mamaduka What do you both think about making block themes default to HTML5 markup? BTW The change in this ticket impacts non-block content in block themes.

[hellofromTonya]

Changing this ticket to blessed task as block theme and code for this change were introduced in 5.9.

[Mamaduka]

@hellofromTonya

I agree that block themes should use HTML5 by default.

[hellofromTonya]

w00t thanks @Mamaduka!

Alrighty, marking ​PR 2109 for commit.

[Mamaduka]

Thanks for working on this, @costdev and @hellofromTonya.

Your summary about the decision in the code comment is :chef's kiss emoji:

[hellofromTonya]

[caption] from original non-block content: before and after patch applied.

[hellofromTonya]

[gallery] from original non-block content: before and after patch applied.

[hellofromTonya]

Self-assigning for commit.

[hellofromTonya]

In 52439:

Themes: Make block themes support HTML5 by default.

For block themes, [52369] added HTML5 support for 'comment-list', 'comment-form', 'style', and 'script'. However, when sites upgrade to 5.9 with non-block content such as a gallery and caption, the markup was not HTML5.

This commit adds full HTML5 theme feature support for block themes. Non-block content such as a [gallery] and [caption] shortcodes will natively be in HMTL5 markup without block themes needing to specifically add add_theme_support( 'html5, .. ) to the theme.

Follow-up to [24417], [27302], [34261], [52369], [52383], [52386].

Props @joyously, costdev, hellofromTonya, audrasjb, Mamaduka, ocean90.
Fixes #54731. See #54597.

[hellofromTonya]

In 52440:

Coding Standard: Remove empty space at end of inline comment in _add_default_theme_supports().

Follow-up to [52439].

See #54731.

Committed via https://core.trac.wordpress.org/changeset/52439.