I searched the Irish Family History online database at ROOTSIRELAND.IE. It has abt 20M B/M/D records for most Irish counties. Records before 1863 are increasingly sparse: almost non-existant before 1800.
For Ann(abell) and J(ames) marriage 1850 +/- 10 yrs, somewhere in Ireland (including Donegal), I found 0 records.
Sporadically, small amounts of newly discovered records are added to this database. Suggest you visit the database, register (free), browse (free), and opt (also free) to be notified as records are added to it.