Villagers only have 8 inventory slots to store items, however, the client still shows villagers picking up items even when these slots are full and they have no space in their inventory anymore. Server-side the villager never picked up these items.

This started occuring in 1.14.2 Pre-Release 1. 1.14.1 didn't have this issue. Possibly introduced with the changes made to fix MC-140174.

When the player picks up these non-existent (for the client) items no pickup sound is played.

The bug is now slightly different in 1.14.3 Pre-Release 1: This does not occur for potatoes or carrots anymore. It looks like villagers can now only hold up to 4 stacks of potatoes, and up to 4 stacks of carrots, and will not attempt to pick up more than this. (Is that intended? I assume this was introduced as part of the fix for MC-74407, but it seems rather strange.) The issue still occurs for bread, wheat, and wheat seeds.