bookdown 项目中的 Rmd 文件名中包含这种类型的字符 Naïve-Bayes.Rmd，使用 bookdown::render_book('index.Rmd') 会报这种如下错误

Error in check_special_chars(files) : 
  Filenames must not contain special characters
Calls: <Anonymous> ... setdiff -> as.vector -> source_files -> check_special_chars
In addition: Warning message:
In check_special_chars(files) :
  The filename "05-Na?ve-Bayes.Rmd" contains special characters. You may rename it to, e.g., "05-Na-ve-Bayes.Rmd".
Execution halted

Exited with status 1.

根据错误提示，我运行

bookdown:::check_special_chars('Naïve-Bayes.Rmd')
[1] "Naïve-Bayes.Rmd"

结果是没问题，继续查 bookdown:::check_special_chars

function (filename) 
{
    reg = rmarkdown:::.shell_chars_regex
    for (i in grep(reg, filename)) warning("The filename \"", 
        filename[i], "\" contains special characters. ", 
        "You may rename it to, e.g., \"", gsub(reg, "-", 
            filename[i]), "\".")
    if (!is.null(i)) 
        stop("Filenames must not contain special characters")
    filename
}
<bytecode: 0x0000005a61fe7c30>
<environment: namespace:bookdown>

继续查 rmarkdown:::.shell_chars_regex

rmarkdown:::.shell_chars_regex
[1] "[ <>()|\\:&;#?*']"

没说不允许这种字符，继续查，不使用 bookdown::render_book 而使用 rmarkdown::render

rmarkdown::render('05-Naïve-Bayes.Rmd')

processing file: 05-Na<U+00EF>ve-Bayes.Rmd
  |.................................................................| 100%
  ordinary text without R code


output file: 05-Na<U+00EF>ve-Bayes.knit.md

"C:/PROGRA~3/CHOCOL~1/bin/pandoc" +RTS -K512m -RTS 05-Naïve-Bayes.utf8.md --to html4 --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash+smart --output 05-Naïve-Bayes.html --email-obfuscation none --wrap preserve --standalone --section-divs --table-of-contents --toc-depth 3 --template "D:\library\bookdown\templates\gitbook.html" --highlight-style pygments --number-sections --css style.css --include-in-header "C:\Users\xy-huang\AppData\Local\Temp\RtmpOOXf8D\rmarkdown-strd545e286996.html" --mathjax --metadata pagetitle=05-Naïve-Bayes.utf8.md 

Output created: final-words.html

自然 knitr::knit 也不会有毛病

knitr::knit('05-Naïve-Bayes.Rmd')


processing file: 05-Na<U+00EF>ve-Bayes.Rmd
  |.................................................................| 100%
  ordinary text without R code


output file: 05-Na<U+00EF>ve-Bayes.md

[1] "05-Naïve-Bayes.md"

看起来没毛病，首先我认为 Naïve-Bayes.Rmd 文件名应该被允许，不然那些德文该怎么破，从上面的追查结果看也是允许这种文件名的，那么问题来了，这报错来自bookdown的哪里？怀疑可能是某个隐藏颇深的编码转化问题？

下附环境信息

xfun::session_info(c('rmarkdown','bookdown'))
R version 3.6.0 (2019-04-26)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 8.1 x64 (build 9600), RStudio 1.2.1335

Locale:
  LC_COLLATE=Chinese (Simplified)_China.936  LC_CTYPE=Chinese (Simplified)_China.936   
  LC_MONETARY=Chinese (Simplified)_China.936 LC_NUMERIC=C                              
  LC_TIME=Chinese (Simplified)_China.936    

Package version:
  base64enc_0.1.3 bookdown_0.11   digest_0.6.19   evaluate_0.14   glue_1.3.1      graphics_3.6.0 
  grDevices_3.6.0 highr_0.8       htmltools_0.3.6 jsonlite_1.6    knitr_1.23      magrittr_1.5   
  markdown_1.0    methods_3.6.0   mime_0.6        Rcpp_1.0.1      rmarkdown_1.13  stats_3.6.0    
  stringi_1.4.3   stringr_1.4.0   tinytex_0.13    tools_3.6.0     utils_3.6.0     xfun_0.7       
  yaml_2.2.0     

Pandoc version: 2.7.2

重现本问题，只需执行以下三步

打开 RStudio 新建 bookdown 项目
将其中某个 Rmd 文件如 05-application.Rmd 重命名为 05-Naïve-Bayes.Rmd
运行 bookdown::render_book('index.Rmd') 即重现问题

traceback() 定位到 check_special_chars

bookdown::render_book('index.Rmd')
Error in check_special_chars(files) : 
  Filenames must not contain special characters
In addition: Warning message:
In check_special_chars(files) :
  The filename "05-Na?ve-Bayes.Rmd" contains special characters. You may rename it to, e.g., "05-Na-ve-Bayes.Rmd".
> traceback()
6: stop("Filenames must not contain special characters")
5: check_special_chars(files)
4: source_files(format, config)
3: as.vector(x)
2: setdiff(source_files(format, config), main)
1: bookdown::render_book("index.Rmd")

问题可能是把文件名中的字符给转换坏了，比如转成问号 ?