Expand output of interpolation

[hektor]

I would like to create a snippet to make a choice from a list of options. As UltiSnips supports
choices via the ${1|<choice-1>,...,<choice-n>|} syntax I was wondering if there is any way to use shell code interpolation to generate the choice syntax.

When I use the following snippet

snippet fontnames_snippet "Snippet for fontnames"
${1|`cat /tmp/fontnames.txt | sort | uniq | awk 'NF' | paste -sd ','`|}
endsnippet

UltiSnips expands to the following:

${1|Adobe Courier Bold,...,STIXMathJax_Variants-Regular|}

where I would actually like to expand this again to get the desired menu of choices.
Is there a way to achieve this with UltiSnips?

[BertrandSim]

This can be done through the expansion of an anonymous snippet:

global !p

def font_names_choicer(snip, filename):
	file = open(filename, "r")
	font_names = file.readlines()
	snip.expand_anon('${1|' + ','.join(font_names) + '|}')

endglobal


post_jump "font_names_choicer(snip, '/tmp/fontnames.txt')"
snippet fontnames_snippet "Snippet for fontnames"
endsnippet

In the above,
'${1|' + ','.join(font_names) + '|}' results in something of the form ${1|Adobe Courier Bold,...,STIXMathJax_Variants-Regular|}, which then gets expanded through expand_anon().