Ender Pearling through a nether portal in the over-world tp's you to the portals nether coordinates but in the overworld

Confirmed for 15w43c.
Same thing happens when you do it in the Nether.

Confirmed for 15w44a.

Affects Version Minecraft 15w45a [ 15408 ]

Confirmed for 15w46a.

same bug? MC-90605

Confirmed for 16w15a. Was hard to even find this bug, since nobody seems to have checked it for a long time.

I would like to add that if you disconnect from a multiplayer server while in a portal, when you reconnect you will spawn in the nether with the coordinates you had in the overworld.

I'm thousands of blocks away from a valid portal. It seems that it's possible to have your overworld coordinates in the nether, and your nether coordinates in the overworld. Wasn't sue if this is worthy of it's own issue as these two issues are probably related.

Fix for 1.10 based on MCP:

diff --git a/src/minecraft/net/minecraft/entity/projectile/EntityThrowable.java b/src/minecraft/net/minecraft/entity/projectile/EntityThrowable.java
index e4c8044..1ab602e 100644
--- a/src/minecraft/net/minecraft/entity/projectile/EntityThrowable.java
+++ b/src/minecraft/net/minecraft/entity/projectile/EntityThrowable.java
@@ -125,60 +125,65 @@ public abstract class EntityThrowable extends Entity implements IProjectile
 
     /**
      * Updates the velocity of the entity to a new value.
      */
     public void setVelocity(double x, double y, double z)
     {
         this.motionX = x;
         this.motionY = y;
         this.motionZ = z;
 
         if (this.prevRotationPitch == 0.0F && this.prevRotationYaw == 0.0F)
         {
             float f = MathHelper.sqrt_double(x * x + z * z);
             this.rotationYaw = (float)(MathHelper.atan2(x, z) * (180D / Math.PI));
             this.rotationPitch = (float)(MathHelper.atan2(y, (double)f) * (180D / Math.PI));
             this.prevRotationYaw = this.rotationYaw;
             this.prevRotationPitch = this.rotationPitch;
         }
     }
 
     /**
      * Called to update the entity's position/logic.
      */
     public void onUpdate()
     {
         this.lastTickPosX = this.posX;
         this.lastTickPosY = this.posY;
         this.lastTickPosZ = this.posZ;
         super.onUpdate();
 
+        if (this.isDead)
+        {
+            return;
+        }
+
         if (this.throwableShake > 0)
         {
             --this.throwableShake;
         }
 
         if (this.inGround)
         {
             if (this.worldObj.getBlockState(new BlockPos(this.xTile, this.yTile, this.zTile)).getBlock() == this.inTile)
             {
                 ++this.ticksInGround;
 
                 if (this.ticksInGround == 1200)
                 {
                     this.setDead();
                 }
 
                 return;
             }
 
             this.inGround = false;
             this.motionX *= (double)(this.rand.nextFloat() * 0.2F);
             this.motionY *= (double)(this.rand.nextFloat() * 0.2F);
             this.motionZ *= (double)(this.rand.nextFloat() * 0.2F);
             this.ticksInGround = 0;
             this.ticksInAir = 0;
         }
         else
         {
             ++this.ticksInAir;
         }

Related to MC-98153, MC-89928, MC-90062. If these did not exist you would just be teleported through twice and arrive where you started I think.

To reproduce this easier, try to throw the ender pearl diagonally into the portal, preferably from the bottom of the portal up. The important thing is that the pearl (which is very fast) is inside any portal block for at least a few ticks (maybe one is enough, I don't know). It doesn't collide with the portal, so it flies through if the game doesn't notice that it's inside the portal fast enough and teleports it. But if it stays in the portal block for a few ticks, it definitely gets teleported. Maybe the reason why this is hard to reproduce is related to MC-4581.