translation exports do not respect nplurals properly

[Dennis Schridde]

For nplurals=3 Launchpad sometimes just creates 2 plural forms, which gives this gettext error:
rm -f pl.gmo && /usr/bin/gmsgfmt -c --statistics -o pl.gmo pl.po
pl.po:7: nplurals = 3...
pl.po:12256: ...but some messages have only 2 plural forms
/usr/bin/gmsgfmt: found 1 fatal error

Affected was for example: https://translations.launchpad.net/warzone2100/2.1/+pots/warzone2100/pl/+translate

[Diogo Matsubara (matsubara)]

Setting to incomplete and assigning to Jeroen.

Jeroen, please help triage this one and set it back to Confirmed, Triaged, Invalid or Won't Fix as appropriate.

[Dennis Schridde (devurandom)]

"Incomplete" as in information missing? Can I provide something in addition?

[Dennis Schridde (devurandom)]

Attached is a file Launchpad(-librarian) generated from this translation:
https://translations.launchpad.net/warzone2100/2.1/+pots/warzone2100/pl/+translate

[Dennis Schridde (devurandom)]

Attached is a file Launchpad(-librarian) generated from this translation:
https://translations.launchpad.net/warzone2100/2.1/+pots/warzone2100/pl/+translate

Error message:
rm -f pl.gmo && /usr/bin/gmsgfmt -c --statistics -o pl.gmo pl.po
pl.po:7: nplurals = 3...
pl.po:12263: ...but some messages have only 2 plural forms
/usr/bin/gmsgfmt: found 1 fatal error

[Jeroen T. Vermeulen (jtv)]

This appears to be an export bug when translation forms are missing: out of the 3 forms this translation uses, if form 2 is not translated, it is not included in the export. For an untranslated message, 2 rather than 3 empty msgstrs are generated.

This is probably something to do with how the exporter finds out how many forms to export: it looks as if it exports up to and including the highest translated form, and in the problem cases, picks a bad default number of forms (either when there is no highest translated form, or when it's <2, or when it's below the language's highest form; I can't say from this example).