Bug or Feature? language-less code blocks use "default" formatting

support
1

I add this to a markdown file:

```
@all-contributors add @YOURUSERNAME for YOURCONTRIBUTIONTYPE
```

Screenshot2026-04-1601-24-43
Screenshot2026-04-1601-24-43757×120 5.13 KB

and Hugo is rendering it in the hugo-default dark theme (even with me having defined styles in css for highlighting)

I add this:

```plaintext
@all-contributors add @YOURUSERNAME for YOURCONTRIBUTIONTYPE
```

Screenshot2026-04-1601-25-58
Screenshot2026-04-1601-25-58777×122 6.27 KB

and it’s showing up in the color scheme I set.

Also… it reacts to my custom css additions that do some magic with the data properties.

This is either a bug or something expected. If my code block DOES NOT have a language type added it will default to the standard theme and does NOT add any of the options I set (like noClassesin this case).

My config in config/*/markup.toml is this:

[highlight]
anchorLineNos = true
codeFences = true
noClasses = false
[goldmark.renderer]
unsafe = true # meh, no like, but required for contributors list

and I added the styles for “my” theme to the stylesheet. “MY” theme is not a dark them (gruvbox-light I think). The theme is exported into a stylesheet via hugo gen chromastyles --style=gruvbox-light > assets/ananke/css/highlighting.css.

Is this A) a bug or B) some issue in my configuration? (repo is here)

We are on the latest Hugo version.

2

Yeah, this is known (at least to me) behavior, but we should document it here:
https://gohugo.io/content-management/syntax-highlighting/#lang

And perhaps some other places too (short code, highlight function). I’ll create a docs issue.

There’s a related proposal here:

I looked into this a while ago, and decided to bail but I don’t remember why.

For now, to meet your needs, I would create a codeblock render hook and set the lang to text if not specified.

3

And this may be useful:

https://discourse.gohugo.io/t/add-option-to-use-default-chroma-lexer-for-code-fences-with-no-language/55368/3

The render hook (layouts/_markup/render-codeblock.html) is trivial:

{{- $lang := "text" }}
{{- $options := .Options }}
{{- if transform.CanHighlight .Type }}
  {{- $lang = .Type }}
{{- else }}
  {{- $options = .Attributes }}
{{- end }}

{{- transform.Highlight .Inner $lang $options }}
1 Like
4

Yeah, pushing it through a render hook might be a good idea.

5

I remember now. I decided to bail because, without a language specified in the info string, a fenced code block renders identically to an indented code block. Since you can’t specify a language with an indented block anyway, this is arguably the expected behavior.