Country code or language code (or language tag)

[747]

75.1. Translating built-in labels

When converting to DocBook, you can rely on the DocBook toolchain to translate (most) built-in labels. To activate this feature, simply set the lang attribute to a valid country code (which defaults to en for English).

A.2. Built-in Attributes

Attribute name	Description	Default value	Allowed values	Header only	See also
lang	Set the value of the lang attribute on the root element of the output document.	en	Valid XML country code	✔	Translating built-in labels

(emphasis by me)

The country code and the language code are different standards (ISO 3166-1 and ISO 639), and there's no "country code for English". Moreover, there's neither "XML country code" nor "XML language code", by which I think you mean language tag (BCP 47), which is the only binding standard in the XML spec among them.

This confusion brings about actual contradictions in your assets in https://github.com/asciidoctor/asciidoctor/tree/master/data/locale, namely:

• misnomers if it means country code (or locale)

  • ar: Argentina, not any Arabic countries
  • ca: Canada, not Catalonia
  • cs: reserved for former Serbia and Montenegro, not Czech
  • fa: nonexistent
  • ja: reserved for Jamaica, not Japan
  • nb: nonexistent
  • nn: nonexistent
  • pt_BR: invalid even as Portugal's subdivision
  • sr: Suriname, not Serbia
  • sr_Latn: invalid even as Suriname's subdivision
  • sv: El Salvador, not Sweden
  • uk: reserved for United Kingdom, not Ukraine
  • zh_CN, zh_TW: nonexistent

• misnomers if language code

  • kr: Kanuri, not Korean
  • pt_BR, sr_Latn, zh_CN, zh_TW: no such format

• misnomers if language tag

  • kr: Kanuri, not Korean

Strictly speaking, subtags of a language tag need to be connected by hyphen, not underscore.

[mojavelinux]

The documentation has been updated to clarify that the value of the lang attribute must be a BCP 47 language tag. That's because the attribute value is passed directly to the lang attribute or xml:lang attribute for HTML and DocBook, respectively.

If you believe that one of the locale files is named incorrectly and needs to be changed, feel free to submit a pull request to correct it.