Here is the summary of this lighting bug I encountered while moving through the 1.14 snapshots on my 1.14 survival world.

What should be happening:
The light within enclosed buildings should only come from light-emitting blocks, windows, and doors that lead outside, and the night time should not affect the edges or corners of building interiors. Update: Light-emitting blocks should be emitting light around them according to their specifications.

What actually happens:
The light from the outside area passes through the solid blocks on my Minecraft buildings, creating weird lighting effects. In the day, this light illuminates the interior of the buildings as if it the ceiling was missing. In the night, a black shadowy area forms on the edges and corners of the interiors of the buildings. Update: I have now noticed areas within my mountain base and my underground railway tunnel with no light at all, daylight or light-emitting blocks, even when I place lanterns in the areas. You'll find this occurrence in one of the newer screenshots.

Steps to reproduce this lighting bug:
1. Create a world with of the current 1.14 snapshots.
2. Make a complex medium-sized building that reaches a high altitude with a ceiling still covering it, preferably a medieval house with a tall tower.
3. Go far away from the building until the chunk(s) unloads, then return back to the building and go to the high altitude area of the building. It should be lit up by skylight in the day without any light-emitting blocks. And at night, it should have a black shadowy area on the edges and corners if you place light-emitting blocks.