R notebook: Rmd and html do not match

Question

I have a .Rmd

---
title: "R Notebook"
output: html_notebook
---

```{r}
dplyr::glimpse(cars)
```

When I execute the chunk, I get the expected output:

However when previewing the notebook I see artifacts:

What is going on here? I restarted R, and cleared knitr cache but no luck.

> version
               _                           
platform       x86_64-conda-linux-gnu      
arch           x86_64                      
os             linux-gnu                   
system         x86_64, linux-gnu           
status                                     
major          4                           
minor          0.3                         
year           2020                        
month          10                          
day            10                          
svn rev        79318                       
language       R                           
version.string R version 4.0.3 (2020-10-10)
nickname       Bunny-Wunnies Freak Out   

Answer 1

Unfortunately, this is only a partial answer (and too long a comment) but it can address at least some confusion.

1.) The problem you have is not new; rather, it is well-known. See the (unanswered) questions here and here. Also, it does not depend on your specific R session but rather seems to be a general HTML/knitr problem that needs to be fixed. Also, if you google your spurious ASCII color codes there A LOT of Rmd and knitr files popping up with people having the exact same problem, even on CRAN or RStudio pages! (Exhibit A)

2.) What you see, are ASCII color codes that are due to the grey <dbl> text and the otherwise white text output. More specifically, they stem from the 256-color extended color set that has the general form \u001b[38;5;${ID}m (Source: second link above).

Sadly, I don't know exactly how to solve the issue but you can at least circumvent it by using only Base R functions that do not change the color scheme within the output! If I come up with a full-fledged answer, I will edit this partial one accordingly.