Lists of data frames do not render as Markdown tables (md_table_parser)

[math-mcshane]

Describe the bug
Lists of tables no longer/don't render inside of Quarto -- e.g., Markdown tables

To Reproduce
This Quarto document will fail to render to HTML or markdown. It will succeed when rendering to PDF. And, within-RStudio table-rendering will use the Markdown version, so you can run this code chunk when format: pdf (or any format) and it will, of course, also fail.

---
format: html
---

```{r}
list(data.frame(a = 1:2), data.frame(b = 1:3)) |> 
  knitr::kable() |>
  kableExtra::kable_styling()
```

It looks like an issue inside of kableExtra:::md_table_parser

I seem to recall this working before, but have run into this error a couple of times. My guess is that this stopped working when issue #821 was fixed (but I'm not sure).

[dmurdoch]

This is really not a kableExtra bug, it's a bug in knitr, or Quarto, or RStudio.

The problem is that calling kable() on a list of dataframes calls the knitr::kables() function, and it defaults to format="pipe". So one workaround is to specify the format, i.e. use

list(data.frame(a = 1:2), data.frame(b = 1:3)) |> 
  knitr::kable(format = "html") |>
  kableExtra::kable_styling()

Another workaround is to use kableExtra::kbl() instead of knitr::kable(), because it is better at figuring out the format automatically.

I suspect there's another workaround: don't use RStudio for this. A very similar document using R Markdown instead of Quarto works find if you call it with rmarkdown::render(), but fails if you try to render it by clicking knit in RStudio. I can't tell you if something similar is possible with Quarto, because I never use it.

[dmurdoch]

See #884 for the R Markdown version.

[math-mcshane]

Hi, actually this is certainly a kableExtra issue. The kableExtra:::md_table_parser internal function is at issue. I just happened to notice it when using RStudio; but it's a problem when producing a markdown table.

CC @haozhu233

[dmurdoch]

The problem is that kableExtra doesn't fully support pipe format, but that's what your code produces. kableExtra sometimes tries to handle pipe format, but the support is limited and (as far as I know) undocumented.

[math-mcshane]

The problem is that kableExtra doesn't fully support pipe format, but that's what your code produces. kableExtra sometimes tries to handle pipe format, but the support is limited and (as far as I know) undocumented.

Sounds like an issue that should be re-opened then

[haozhu233]

Yeah, as @dmurdoch mentioned, the support on the pipe markdown tables is very limited. Previously, my rule of thumb was that it should try to return as is, or at least should not trigger an error. I will take a look at this.