How to source() .R file saved using UTF-8 encoding?

Question

The following, when copied and pasted directly into R works fine:

> character_test <- function() print("R同时也被称为GNU S是一个强烈的功能性语言和环境，探索统计数据集，使许多从自定义数据图形显示...")
> character_test()
[1] "R同时也被称为GNU S是一个强烈的功能性语言和环境,探索统计数据集,使许多从自定义数据图形显示..."

However, if I make a file called character_test.R containing the EXACT SAME code, save it in UTF-8 encoding (so as to retain the special Chinese characters), then when I source() it in R, I get the following error:

> source(file="C:\\Users\\Tony\\Desktop\\character_test.R", encoding = "UTF-8")
Error in source(file = "C:\\Users\\Tony\\Desktop\\character_test.R", encoding = "utf-8") : 
  C:\Users\Tony\Desktop\character_test.R:3:0: unexpected end of input
1: character.test <- function() print("R
2: 
  ^
In addition: Warning message:
In source(file = "C:\\Users\\Tony\\Desktop\\character_test.R", encoding = "UTF-8") :
  invalid input found on input connection 'C:\Users\Tony\Desktop\character_test.R'

Any help you can offer in solving and helping me to understand what is going on here would be much appreciated.

> sessionInfo() # Windows 7 Pro x64
R version 2.12.1 (2010-12-16)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United Kingdom.1252 
[2] LC_CTYPE=English_United Kingdom.1252   
[3] LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C                           
[5] LC_TIME=English_United Kingdom.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods  
[7] base     

loaded via a namespace (and not attached):
[1] tools_2.12.1

and

> l10n_info()
$MBCS
[1] FALSE

$`UTF-8`
[1] FALSE

$`Latin-1`
[1] TRUE

$codepage
[1] 1252

Answer 1

On R/Windows, source runs into problems with any UTF-8 characters that can't be represented in the current locale (or ANSI Code Page in Windows-speak). And unfortunately Windows doesn't have UTF-8 available as an ANSI code page--Windows has a technical limitation that ANSI code pages can only be one- or two-byte-per-character encodings, not variable-byte encodings like UTF-8.

This doesn't seem to be a fundamental, unsolvable problem--there's just something wrong with the source function. You can get 90% of the way there by doing this instead:

eval(parse(filename, encoding="UTF-8"))

This'll work almost exactly like source() with default arguments, but won't let you do echo=T, eval.print=T, etc.