Irish: With the preposition chuig, do adjectives and other parts of compound nouns need to mutate?
With the preposition chuig, do adjectives and other parts of compound nouns need to mutate too? That is, do they need to be placed into dative forms? Maybe the examples I am using below aren't good examples. For instance, siopa doesn't have a different dative form and deas seems to be deasa in both the plural nominative and plural dative. Hmmm. Perhaps you could provide some examples where things would actually need to be altered if they do?

chuig (an) siopa = to a/the shop
chuig (na) siopaí = to (the) shops

chuig (an) siopa leabhar = to a/the bookshop
chuig (na) siopaí leabhar = to (the) bookshops

chuig (an) siopa leabhar deas = to a/the nice bookshop
chuig (na) siopaí leabhar deasa = to (the) nice bookshops

Question

Irish: With the preposition chuig, do adjectives and other parts of compound nouns need to mutate?
With the preposition chuig, do adjectives and other parts of compound nouns need to mutate too? That is, do they need to be placed into dative forms? Maybe the examples I am using below aren't good examples. For instance, siopa doesn't have a different dative form and deas seems to be deasa in both the plural nominative and plural dative. Hmmm. Perhaps you could provide some examples where things would actually need to be altered if they do?

chuig (an) siopa = to a/the shop
chuig (na) siopaí = to (the) shops

chuig (an) siopa leabhar = to a/the bookshop
chuig (na) siopaí leabhar = to (the) bookshops

chuig (an) siopa leabhar deas = to a/the nice bookshop
chuig (na) siopaí leabhar deasa = to (the) nice bookshops

Answer

The dative case for adjectives is identical to the nominative case, so they don't change; however, in Ulster Irish the adjective will be lenited in the dative singular with both masculine and feminine nouns when the article is present (I believe in such cases some Munster dialects eclipse the adjective):

Feminine noun
U: chuig an phictiúrlann/phictiúrlainn bheag 
C/M: chuig an bpictiúrlann/bpictiúrlainn bheag
(M: chuig an bpictiúrlann/bpictiúrlainn mbeag)

Masculine noun
U: chuig an ghort bheag
C/M: chuig an ngort beag
(M: chuig an ngort mbeag)

There's no change in the dative plural (in some dialects there is a dative plural ending -ibh which is added to nouns and sometimes adjectives, you may come across this in reading, but don't worry about using it).
In compound nouns, only the head noun is inflected, the rest of the construction doesn't change.