tikzDevice produces a non-UTF-8 output file on Windows

[julianre]

The TeX/TikZ files generated by tikzDevice are not encoded in UTF-8 but in the Windows 1252 file encoding (under Windows, see Session Info). This results in a problem, if the plot is included in the main LaTeX document (UTF-8 encoding). In my case (MWE), I receive the following error message:

pandoc.exe: Cannot decode byte '\xd6': Data.Text.Internal.Encoding.streamDecodeUtf8With: Invalid UTF-8 stream Error: pandoc document conversion failed with error 1

Minimal working example (RMarkdown file):

---
title: "test"
author: "test"
date: "Today"
output: 
  pdf_document: 
header-includes:
   - \usepackage{tikz}
---
```{r setup, include=FALSE}
library(tikzDevice)
options(tikzDefaultEngine = "xetex")

x <- rnorm(50)
y <- rnorm(50)

plot(x, y, xlab = "ÖÄÜ", ylab = "öäü")

I tried the MWE under Ubuntu and the generated file is encoded in UTF-8 (no problem). 

xfun::session_info()

R version 3.6.1 (2019-07-05) Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows 10 x64 (build 18362), RStudio 1.2.1335

Locale: LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252
LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
LC_TIME=German_Germany.1252

Package version: compiler_3.6.1 evaluate_0.14
filehash_2.4-2 glue_1.3.1
graphics_3.6.1 grDevices_3.6.1
grid_3.6.1 highr_0.8
knitr_1.24 magrittr_1.5
markdown_1.1 methods_3.6.1
mime_0.7 png_0.1.7
rstudioapi_0.10 stats_3.6.1
stringi_1.4.3 stringr_1.4.0
tikzDevice_0.12.3 tools_3.6.1
utils_3.6.1 xfun_0.9
yaml_2.2.0

[rstub]

Thanks for the report. Besides the workarounds mentioned on SO, you could also try to tell LaTeX to read the file using Windows 1252 encoding instead of the default UTF-8:

options( tikzLatexPackages = c(getOption( "tikzLatexPackages" ),
                               "\\usepackage[cp1252]{inputenc}" ))

(Completely untested since I am not on Windows right now ...)

[rstub]

Maybe related: Encoding problems on Linux at https://stackoverflow.com/q/58401825/8416610