`attr_list` values are included in social card's title, if set for h1 header

[Andre601]

Context

No response

Bug description

When using the attr_list extension alongside the Social plugin and then set a attribute for the h1 header (i.e. a custom header ID) does the social plugin include the attribute in the title of the image.

Example (From reproduction):

# Hello world! { #hello }

Lorem ipsum dolor.

Resulting card:

Related links

• Reporting a bug

Reproduction

9.5.49-social-cards-display-issue.zip

Steps to reproduce

1. Add social to the plugins option
2. Add attr_list to the markdown_extensions option
3. Build docs
4. Check generated image in .ache folder.

Browser

Firefox

Before submitting

• I have read and followed the bug reporting guidelines.
• I have attached links to the documentation, and possibly related issues and discussions.
• I assure that I have removed all customizations before submitting this bug report.
• I have attached a .zip file with a minimal reproduction using the built-in info plugin.

[squidfunk]

Thanks for reporting. So, I've investigated, and it seems that this comes from MkDocs mutating the Page.title in between on_page_markdown and on_page_content, replacing it with Page._title_from_render. First, the Markdown page title is used, which is also used by the social plugin, but later, it returns the rendered title.

We can mitigate the issue on our side by switching to on_page_content, as we now do in 6d1ef25.

IMHO, this is misleading, as the same property has different values depending on the hook used, and must thus be fixed in MkDocs. It tries to do a best effort to return any title, not carrying about the specifics. Since this possibly impacts a lot of plugins, may I kindly ask you to create an upstream issue? Here's a hook with a minimal reproduction:

def on_page_markdown(markdown, page, config, files):
    print("on_page_markdown", page.title)

def on_page_content(html, page, config, files):
    print("on_page_content", page.title)

INFO    -  Cleaning site directory
INFO    -  Building documentation to directory: 9.5.49-social-cards-display-issue/site
on_page_markdown <em>Hello</em> *world!!!* { #hello }
on_page_content Hello world!!!
INFO    -  Documentation built in 0.14 seconds

[squidfunk]

Note that inconsistent title handling is one of the major pain points of MkDocs:

• Header and navigation sidebars display incorrectly arbitrary markup mkdocs/mkdocs#3357 (76 comments)
• Consider changing the precedence of title sources mkdocs/mkdocs#3532
• Expose a page.content_title attribute mkdocs/mkdocs#3533 (stale PR)
• Full-featured text extraction from the first H1 heading mkdocs/mkdocs#3578 (partial revert to pre-1.5)

The first issue is the second-most commented issue for MkDocs, but IMHO, it is still unfixed albeit the issue being closed, so I think the maintainers will probably tackle this as part of the next iteration of MkDocs they are currently working on. It might be good for them to know a few other corner cases that break, including this one, so reporting it could be beneficial.

[squidfunk]

Released as part of 9.5.50.