Water does not leak through leaves and regular stairs but upside down stairs

Confirmed.

Affects 13w09c. Related to MC-1390 (seems the bugs are just few lines apart). And fix incoming.

Fix

BlockFluid.randomDisplayTick()

...
        if (random.nextInt(10) == 0
                //&& world.doesBlockHaveSolidTopSurface(x, y - 1, z)
                && world.getBlockMaterial(x, y - 1, z).blocksMovement()
                && !world.getBlockMaterial(x, y - 2, z).blocksMovement()) {
            var21 = (double) ((float) x + random.nextFloat());
            var22 = (double) y - 1.05D; // <== MC-1390 ?
            var23 = (double) ((float) z + random.nextFloat());

            if (this.blockMaterial == Material.water) {
                world.spawnParticle("dripWater", var21, var22, var23, 0.0D, 0.0D, 0.0D);
            } else {
                world.spawnParticle("dripLava", var21, var22, var23, 0.0D, 0.0D, 0.0D);
            }
        }

Fix tested on 1.4.7, also with fences, iron bars, glass block. Not tested on everything, but if something does not work right, that just means a bit more logic into that if.

I have a leaky roof of brick stairs, rightside-up, dripping from the upper seam (not the lower, apparently). FWIW, it seems similar to the way light "leaks" through the seams on stairs as well. v1.5

Edit: Actually, it might be more accurate to say that it drips from the joins where there is an air-block to either side of it

Further Edit: It occurs to me now that I did NOT see this when the roof was wood, only after I switched to brick

That description is a bit difficult to understand, could you attach a screenshot which shows the setup?

Attachments not cooperating; http://www.drlgraphics.com/images/Minecraft/driperrorexample.png

Can't really show the "drip" without video 😛

Use "More Actions" -> "Attach file" for attaching screenshots. Not "Attach Screenshot"

Attached image

For me, on 1.5, both wood and brick stairs produce similar effect. And while the effects is a little bit like "why do they leak?", it is actually a different issue, and probably will be considered a feature.

At least I could not see any water effects (well) below the stair blocks (unless they were also horizontally right next to a stairs block). Such drops would have indicated "leaking", which this particular JIRA issue is about.

Technically, at least what I saw, was not the dripping (droplets drop down from block's bottom side), but "splashes" (splash up and back down on block's top surface). However, the splashing (and dripping) only consider a single level for the whole block to start from, and since stairs have two levels on the "up" side, it works a little bit better when the effect starts at the half-block level. For the other taller side of stairs, this means the splashes will be inside the block. And that is what at least I could see, the rare splashes that started near the inner surface.

It is possible to "fix" that (as the necessary methods to get the proper surface do exist), but it might be a bit inefficient, and it would certainly be worthy of another issue, for Mojang to decide.

This issue still in 1.5.

Still a concern in 1.7.4/5 and 14w08a

Confirmed for 14w10c and 14w11b

Confirmed for 15w46a

Confirmed for 16w15a and 16w15b

Confirm for 1.9.3 pre-2

Confirmed for 1.9.4

Confirmed for 16w20a

Confirmed for 17w13b

Confirmed for 17w45b

Confirmed for 18w07a

Confirmed for 18w11a

Confirmed for 18w20c

Confirmed for 18w22c

Confirmed for 1.13-pre2

Confirmed for 1.13-pre5

Fixed in 1.13-pre7