This affects the Farming Profession of Villagers from the 1.14 and subsequent versions of Minecraft, it is not known if it will affect villagers generated from earlier versions (pre-1.14).

Tested using minecraft:carrot on the minecraft:composter block which was the workstation of the villager affected.  The villager trade was 22 minecraft:carrot(s) for 1 minecraft:emerald(s).

Can be recreated by composting Carrots in a Composter block while within range of a villager that has a trade for carrots in return for an emerald. This may work with other compostable items.

The villager will continue to hold the emerald in its arms until hotbar slot is changed or another non-trade item is moved into the slot through the inventory.