Lint: warn when knitr classes are used (was: use plot as blog post image)

[produnis]

Hi there,
I am using (quarto 1.4.550), and my problem is that #| class-output: preview-image seems to be ignored. Please find a working example at https://github.com/produnis/testing and have a look at the "Welcome" post. Instead of the first Anscombe plot, the Datasaurus was ment to be used as the preview pic....

Greetings, Joe

Originally posted by @produnis in #2324 (comment)

[dragonstyle]

The issue is that your code cell should be using classes - e.g.:

```{r}
#| label: fig-datasaurus
#| classes: preview-image # <- Note classes name
#| fig-width: 8
#| fig-height: 8
library(ggplot2)
load(url("https://www.produnis.de/nagut/datasaurus.RData"))

datasaurus |> 
  ggplot(aes(x=x, y=y)) +
  geom_point() +
  facet_wrap(~dataset)
```

HTH!

[cderv]

As I see you are using #| class-output: preview-image, just a mention that this is the knitr options for text output block: https://yihui.org/knitr/options/#text-output

Different from classes which applies on cell container more globally (https://quarto.org/docs/reference/cells/cells-knitr.html#attributes)

[produnis]

thanks for your answer....
so, the problem was 30cm next to the monitor... :/

using #| classes: preview-image instead of #| class-output: preview-image it works!

[dragonstyle]

It was super helpful that you included the source file - made it easy to see the problem rather than try to stumble through. Thank you!!!

[cscheid]

I'm going to reopen this and file it for our future linter.