fix: normalize Html subclasses in as_html for correct f-string formatting#8223
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mscolnick merged 1 commit intomarimo-team:mainfrom Feb 10, 2026
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When `mo.as_html(mo.md("# Title"))` is used in an f-string, Python calls
`__format__` on the returned object. Since `_md` overrides `__format__`
to return raw markdown (to support nested `mo.md()` calls), the f-string
produces raw markdown instead of HTML.
Fix by normalizing Html subclasses to plain Html objects in `as_html()`,
so that `__format__` returns processed HTML text.
Closes marimo-team#7931
Contributor
|
@Light2Dark i know you were looking at this before. what do you think of this approach? |
Collaborator
|
I think this should be an improvement over the original behaviour. Tested it with the smoke tests However, nested markdown and nested md in Html still doesn't work cleanly. You'd need to call eg. #7931 (comment) solution = mo.md("**the solution**")
mo.md(rf"""
<details>
<summary>
Solution
</summary>
{solution}
</details>
""") |
Light2Dark
approved these changes
Feb 10, 2026
|
🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.19.10-dev35 |
mscolnick
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Feb 10, 2026
…g formatting (#8223)" (#8257) This reverts commit 2d2f100. Commit 2d2f100 changed as_html() to normalize Html subclasses (like Spinner) into plain Html objects. This creates a new object, breaking the identity-based comparison (is not) in output.remove(). When the spinner's context manager exits and calls remove(self), it can't find the spinner in the output list because a different Html object was stored.
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Summary
f"{mo.as_html(mo.md('# Title'))}"returned raw markdown instead of rendered HTML becausemo.md()returns an_mdsubclass that overrides__format__(). Normalizes subclasses to the baseHtmltype so f-string formatting works correctly.Closes #7931
Test Plan
as_html(mo.md(...))returns baseHtmltype