polyglossia, Korean and LuaLaTeX

Question

I'm confused about language names in the polyglossia package. Table 1 on page 5 of the polyglossia documentation lists the language names in lower case (e.g. 'korean', not 'Korean'). But when I try to use the lower case name 'korean' in a document, and run it with LuaLaTeX, I get an error. Here's the MWE:

\documentclass{article}
\usepackage{polyglossia}
\setmainlanguage{korean}
\setmainfont{UnBatang}

\begin{document}
한국
\end{document}

..and here's the error message (I've pretended it's code to make it stand out on stackexchange):

You cannot set field spec in a node of type glue.
\newpage ...k \@nobreakfalse \everypar {}\fi \par
                                              \ifdim \prevdepth >\z@ \vs...

LuaLaTeX appears to work ok with the upper case name 'Korean'.

I don't get this kind of error with the other (3) lower case language names I've tried (russian, farsi and tamil).

Neither upper nor lower case names trigger an error message in XeLaTeX, although the upper case version does give me a rather odd message:

Package polyglossia Warning: No hyphenation patterns were loaded for `orean'
(polyglossia)   I will use \language=\l@nohyphenation instead on input line 6.

--so something has apparently stripped off the upper case 'K'. I get no such message with the lower case 'korean'.

I suppose it's possible that LuaLaTeX is also stripping off the upper case 'K', and as a result polyglossia isn't doing something (like loading hyphenation patterns) that triggers an error in lualatex. In other words, it's possible that the apparent success with the uppercase 'Korean' in lualatex is due to something else that goes wrong.

Is polyglossia supposed to use lowercase or upper case language names?

If this is a bug in lualatex and/or polyglossia (and if language names in polyglossia are supposed to be lower case), is there a better way to work around it than supplying an upper case name for Korean?

Answer 1

The names are supposed to be lowercase. On my system passing Korean even results in a warning:

Package polyglossia Warning: File gloss-Korean.ldf does not exist!
(polyglossia)                I will nevertheless try to use hyphenation pattern
s for Korean. on input line 3.

The korean language file for polyglossia is broken because it tries to set the glue_spec of a glue node, but for two years now the glue_spec is no longer used for this purpose.

You can temporary fix the problemby by finding the file gloss-korean.ldf and changing some lines in there:

Replace (around line 690)

local function get_new_glue (wd, st, sh)
    local glue = node.new("glue")
    local spec = node.new("glue_spec")
    spec.width   = wd
    spec.stretch = st
    spec.shrink  = sh
    glue.spec = spec
    return glue
end

with

local function get_new_glue (wd, st, sh)
    local glue = node.new("glue")
    glue.width   = wd
    glue.stretch = st
    glue.shrink  = sh
    return glue
end

and at line 706 replace

    local hss = get_new_glue(0, 65536, 65536)
    hss.spec.stretch_order = 2
    hss.spec.shrink_order  = 2

with

    local hss = get_new_glue(0, 65536, 65536)
    hss.stretch_order = 2
    hss.shrink_order  = 2

I will send these changes to the polyglossia maintainer but it does not look like there will be any update for polyglossia soon.