I should attach the debugging log from fontconfig too to see what actually happens.
$ FC_DEBUG=4 fc-match monospace:lang=en
...
FcConfigSubstitute Pattern has 2 elts (size 16) family: "monospace"(s) lang: en(s)
FcConfigSubstitute test pattern any lang Contains "ja" FcConfigSubstitute test pattern any family Equal "monospace" Substitute match pattern any lang Contains "ja" pattern any family Equal "monospace" edit Edit family Prepend "VL Gothic";
Prepend list before "DejaVu Sans Mono"(w) "Bitstream Vera Sans Mono"(w) "DejaVu Sans Mono"(w) "Inconsolata"(w) "Andale Mono"(w) "Courier New"(w) "Cumberland AMT"(w) "Luxi Mono"(w) "Nimbus Mono L"(w) "Courier"(w) "monospace"(s) Prepend list after "DejaVu Sans Mono"(w) "Bitstream Vera Sans Mono"(w) "DejaVu Sans Mono"(w) "Inconsolata"(w) "Andale Mono"(w) "Courier New"(w) "Cumberland AMT"(w) "Luxi Mono"(w))) "Nimbus Mono L"(w) "Courier"(w) "VL Gothic"(s) "monospace"(s)
...
For reference: $ FC_DEBUG=4 fc-match sans-serif:lang=en
...
FcConfigSubstitute Pattern has 2 elts (size 16) family: "sans"(s) lang: en(s)
...
FcConfigSubstitute test pattern any family Equal "sans" Substitute match pattern any family Equal "sans" edit Edit family Assign "sans-serif";
Append list before "sans"(s) Append list after "sans"(s) "sans-serif"(w) FcConfigSubstitute editPattern has 2 elts (size 16) family: "sans-serif"(w) lang: en(s)
...
So it just works for sans or sans-serif, because the family name pattern isn't "strong" binding anymore. but not for serif and monospace.
Aside from that, I should inform you a fact of the kind of side-effect of "contains" here. as you may noticed, it also matches "en" too. I don't know if we should avoid using that to do the exact match for lang.
Anyway, the package list and files this issue affects attached. note that it may be missing something if any packages aren't in comps.
Regards, -- Akira TAGOH
baekmuk-ttf-batang-fonts-2.2-24.fc13: 65-baekmuk-ttf-batang.conf baekmuk-ttf-dotum-fonts-2.2-24.fc13: 65-baekmuk-ttf-dotum.conf baekmuk-ttf-gulim-fonts-2.2-24.fc13: 65-baekmuk-ttf-gulim.conf culmus-aharoni-clm-fonts-0.104-2.fc14: 65-culmus-aharoni-clm.conf culmus-david-clm-fonts-0.104-2.fc14: 65-culmus-david-clm.conf culmus-drugulin-clm-fonts-0.104-2.fc14: 65-culmus-drugulin-clm.conf culmus-ellinia-clm-fonts-0.104-2.fc14: 65-culmus-ellinia-clm.conf culmus-frank-ruehl-clm-fonts-0.104-2.fc14: 65-culmus-frank-ruehl-clm.conf culmus-miriam-clm-fonts-0.104-2.fc14: 65-culmus-miriam-clm.conf culmus-miriam-mono-clm-fonts-0.104-2.fc14: 65-culmus-miriam-mono-clm.conf culmus-nachlieli-clm-fonts-0.104-2.fc14: 65-culmus-nachlieli-clm.conf hanazono-fonts-20091003-1.fc13: 66-hanazono.conf ipa-gothic-fonts-003.02-1.fc13: 66-ipa-gothic.conf ipa-mincho-fonts-003.02-1.fc14: 66-ipa-mincho.conf ipa-pgothic-fonts-003.02-1.fc13: 65-ipa-pgothic.conf ipa-pmincho-fonts-003.02-1.fc13: 65-ipa-pmincho.conf kacst-art-fonts-2.0-6.fc14: 67-kacst-art.conf kacst-book-fonts-2.0-6.fc14: 67-kacst-book.conf kacst-decorative-fonts-2.0-6.fc14: 67-kacst-decorative.conf kacst-digital-fonts-2.0-6.fc14: 67-kacst-digital.conf kacst-farsi-fonts-2.0-6.fc14: 67-kacst-farsi.conf kacst-letter-fonts-2.0-6.fc14: 67-kacst-letter.conf kacst-naskh-fonts-2.0-6.fc14: 67-kacst-naskh.conf kacst-office-fonts-2.0-6.fc14: 67-kacst-office.conf kacst-one-fonts-2.0-6.fc14: 67-kacst-one.conf kacst-pen-fonts-2.0-6.fc14: 67-kacst-pen.conf kacst-poster-fonts-2.0-6.fc14: 67-kacst-poster.conf kacst-qurn-fonts-2.0-6.fc14: 67-kacst-qurn.conf kacst-screen-fonts-2.0-6.fc14: 67-kacst-screen.conf kacst-title-fonts-2.0-6.fc14: 67-kacst-title.conf kacst-titlel-fonts-2.0-6.fc14: 67-kacst-titlel.conf knm-new-fixed-fonts-1.1-10.fc13: 69-knm-new-fixed.conf lklug-fonts-0.6-3.20090803cvs.fc14: 65-lklug.conf lohit-assamese-fonts-2.4.3-3.fc13: 66-lohit-assamese.conf lohit-bengali-fonts-2.4.3-4.fc13: 66-lohit-bengali.conf lohit-devanagari-fonts-2.4.3-5.fc13: 66-lohit-devanagari.conf lohit-gujarati-fonts-2.4.4-2.fc13: 66-lohit-gujarati.conf lohit-kannada-fonts-2.4.4-3.fc13: 66-lohit-kannada.conf lohit-malayalam-fonts-2.4.4-4.fc13: 67-lohit-malayalam.conf lohit-oriya-fonts-2.4.3-3.fc13: 66-lohit-oriya.conf lohit-punjabi-fonts-2.4.3-3.fc13: 66-lohit-punjabi.conf lohit-tamil-fonts-2.4.5-2.fc13: 66-lohit-tamil.conf lohit-telugu-fonts-2.4.5-4.fc13: 66-lohit-telugu.conf madan-fonts-2.000-1.fc13: 65-madan.conf samyak-devanagari-fonts-1.2.1-9.fc14: 67-samyak-devanagari.conf samyak-gujarati-fonts-1.2.1-9.fc14: 67-samyak-gujarati.conf samyak-malayalam-fonts-1.2.1-9.fc14: 68-samyak-malayalam.conf samyak-oriya-fonts-1.2.1-9.fc14: 67-samyak-oriya.conf samyak-tamil-fonts-1.2.1-9.fc14: 67-samyak-tamil.conf sarai-fonts-1.0-8.fc13: 68-sarai.conf sazanami-gothic-fonts-0.20040629-9.fc13: 66-sazanami-gothic.conf sazanami-mincho-fonts-0.20040629-9.fc13: 66-sazanami-mincho.conf smc-anjalioldlipi-fonts-04.2-6.fc14: 67-smc-anjalioldlipi.conf smc-dyuthi-fonts-04.2-6.fc14: 67-smc-dyuthi.conf smc-kalyani-fonts-04.2-6.fc14: 67-smc-kalyani.conf smc-meera-fonts-04.2-6.fc14: 66-smc-meera.conf smc-rachana-fonts-04.2-6.fc14: 67-smc-rachana.conf smc-raghumalayalam-fonts-04.2-6.fc14: 67-smc-raghumalayalam.conf smc-suruma-fonts-04.2-6.fc14: 67-smc-suruma.conf thai-scalable-garuda-fonts-0.4.12-2.fc12: 90-thai-scalable-synthetic-garuda.conf thai-scalable-kinnari-fonts-0.4.12-2.fc12: 90-thai-scalable-synthetic-kinnari.conf thai-scalable-umpush-fonts-0.4.12-2.fc12: 90-thai-scalable-synthetic-umpush.conf vlgothic-fonts-20100126-2.fc14: 65-1-vlgothic-gothic.conf vlgothic-p-fonts-20100126-2.fc14: 65-0-vlgothic-pgothic.conf woodardworks-laconic-shadow-fonts-001.001-4.fc12: 60-woodardworks-laconic-shadow.conf wqy-microhei-fonts-0.2.0-0.2.beta.fc13: 65-wqy-microhei.conf wqy-zenhei-fonts-0.9.45-1.fc14: 65-wqy-zenhei.conf