The bug

The interior faces of hoppers appear to render at a continuous light level, rather than being shaded differently depending on direction. This behaviour is inconsistent with cauldrons, where the inner faces are shaded differently depending on direction. Interestingly, minecarts with hoppers are not affected by this problem, and the inner faces are shaded differently as one would expect.

How to reproduce

1. Place a hopper
2. Place a minecart with hopper
3. Place a cauldron
4. Compare the inner faces of all three

Expected results

The inner faces of the hopper would appear at differing brightnesses depending on direction.

Actual results

The brightness appears the same regardless of direction.

Further notes

This issue affected Java Edition until 14w10a, when hoppers were converted over to block models (see also MC-249267). Interestingly, minecarts with hoppers in Java Edition were also shaded correctly even when the placed block forms of hoppers weren't, which is without a doubt due to MC-248703.