The bug

19w08a and above :

Players don't interact with walls correctly.

-Players can have weird interactions with walls in water, by walking against a wall while pressing jump key, then keep walk against the wall without pressing the jump key. It is easier to reproduce if there is slimeblocks below water (Minecraft 19w07a 13_02_2019 20_27_56.mp4)

History :

19w07a :

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19w06a :

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19w05a :

-Slow falling against walls fixed, therefore double jump fixed.

-Interaction with walls in water not fixed (Minecraft 19w05a 30_01_2019 19_05_56.mp4)

19w04b :

-Interaction with walls in water not fixed (Minecraft 19w04b 25_01_2019 13_57_50.mp4)

-Walking on walls partially fixed, player now falls slowly when moving against a wall. Minecraft 19w04b 25_01_2019 14_00_23.mp4 (player)/Minecraft 19w04b 25_01_2019 14_04_10.mp4 (mobs)

-You can now perform a double jump. This bug is very cool, you should consider making an enchantment for boots that acts exactly the same (slow fall if you're against a wall and be able to double jump). This enchantment could be spider related, maybe only obtainable in a chest hidden deep in these cobwebs that are around cave spider spawners in mineshafts. Video : Minecraft 19w04b 25_01_2019 14_33_17.mp4

 -This affects mobs. Videos : Minecraft 19w04b 25_01_2019 14_57_44.mp4 (Zombie double jumping)/Minecraft 19w04b 25_01_2019 15_07_32.mp4 (Creeper double jumping)

19w04a :

Players and mobs hitboxes don't interact with walls correctly.

-You can't jump if you are moving against a wall (this is MC-142913)

-If you jump against a block you'll stand a little bit higher (0.1213 block) if you keep moving forwards.

-If you jump again, this time you'll stand 0.0429 blocks higher.

-If you fall from a high place and trying to move against a wall, the player can stand in the wall. The high you'll end depends of the high you were when you fell. For example, if you're standing 4 blocks high, you'll end 0.65373 block high. This is not proportional : if you're standing 5 blocks high, you'll end 0.15552 block high. If you're standing 150 blocks high, you'll end 1.91484 blocks high.

-You can literally walk on walls (and if you have blocks above your head it reduces your heigh while walking on walls)

-If you are in water, if there is slime blocks below it, and if you walk against the wall the player keeps moving strangely. In order to reproduce it, you need to be against the wall, press jump and move forwards at the same time. Once you're glitched you don't need to press jump anymore. You can reproduce it without slimeblocks but it is a little bit more tricky.

-2 mobs or players are stucked if they are in a 1x1 hole (probably because they are pushing each other against the wall)

See the screenshots and videos attached.