Modelsummary fails on fixest models with clustered SEs and dot aligned columns

[svraka]

See this minimal example:

---
title: Error with dot aligned tables
output: pdf_document
---

```{r}
library(fixest)
devtools::load_all()

m <- feols(mpg ~ wt | cyl, data = mtcars)

modelsummary(m, align = "ld")

Modelsummary adds a GoF with the standard error type "by: cyl", which is not a valid value for siunix:

Rscript -e "rmarkdown::render('.scratch/d1.Rmd', quiet = TRUE)" ! Package siunitx Error: Invalid number ':'.

We can declare it as a non-numeric row with a manual workaround but it would be nice if modelsummary did it automatically:

````markdown
---
title: Fixed dot aligned tables
output: pdf_document
---

```{r}
library(fixest)
devtools::load_all()

m <- feols(mpg ~ wt | cyl, data = mtcars)

modelsummary(m, align = "ld") |>
  tinytable::style_tt(tabularray_inner = "row{12}={guard}")

Note that the X for the fixed effect line caused no issues.

[vincentarelbundock]

I agree that this is not a great user experience, and the fact that the table doesn't compile at all makes this feel like a more serious issue than https://github.com/vincentarelbundock/modelsummary/issues/827

Thanks for posting. I'll think about it.