When villager put in a confined 1x1 square with workstation adjacent in one of the cardinal directions, the villager won't pick up the trade. 

The villager is standing on top of double carpet (as I've found via YouTube to work) with trapdoors confining the villager to a 1x1 space. When a workstation is put in front of villager I would expect the said villager to pick up the trade (during the day at least). This is however not done. 

I've tried to change the trapdoors to other blocks , both full, half and transparent.

When villager is set free and roams into another room (otherwise blocked off) it picks up a barrel and becomes a fisherman. 

In the exact same premises in creative mode it works fine, right of the bat, and the villager does pick up the correct trade - no problems what so ever.