[ruby-core:89459] [Ruby trunk Bug#14127] (CSV) generating UTF-16LE encoded file without BOM

Issue #14127 has been updated by printercu (Max Melentiev).


WDYT about adding `file_header` option or something like this?

It's quite tricky to add this in streaming mode:

```ruby
CSV.open(file, 'wb', encoding: 'utf-16le', headers: headers_row, write_headers: true) do |csv|
  bom_written = false
  for_each_row do |row|
    unless bom_written
      csv.to_io.write(BOM)
      bom_written = true
    end
    csv << row
  end
end
```

----------------------------------------
Bug #14127: (CSV) generating UTF-16LE encoded file without BOM
https://bugs.ruby-lang.org/issues/14127#change-74499

* Author: laykou (Ladislav Gallay)
* Status: Rejected
* Priority: Normal
* Assignee: kou (Kouhei Sutou)
* Target version: 
* ruby -v: 2.4.1
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
This file should contain BOM information so that it is properly detected as UTF-16LE file.

How to generate such file:

~~~ruby
file = CSV.generate(encoding: 'UTF-16LE') do |csv|
    csv << ['something', 'トセナ。ト最・ナセテステ。テュテゥ']
end
~~~

According to `file -I file.csv` this file is recognized as `application/octet-stream; charset=binary` because it is missing the BOM information.

According to Wikipedia https://en.wikipedia.org/wiki/UTF-16 it should contain "\xFF\xFE" on the beginning of the document so that everyone knows iths UTF-16LE.

Here is someone trying to fix this in the similiar way: https://stackoverflow.com/a/22950912/1632815 I did it: manually adding that BOM information.

~~~ ruby
## Adds BOM, albeit in a somewhat hacky way.
new_html_file = File.open(foo.txt, "w:UTF-8")
new_html_file << "\xFF\xFE".force_encoding('utf-16le') + some_text.force_encoding('utf-8').encode('utf-16le')
~~~




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