When I load my pre-1.8 world in 15w31a and go to the end, the dragon respawns automatically! The console reports "Found that the dragon has not yet been killed in this world.", which is incorrect.
The problem seems to be that the game is searching for existing end portal blocks to detect "dragon was killed", but it only searches chunks south and east of 0,0. My existing portal is centered at -26,23 and so none of the portal blocks are found. If I make a copy of the portal at positive X and Z in 1.8 before loading the world in 15w31a, it correctly "Found that the dragon has been killed in this world already."
Comments 6
No, it's not. The ultimate plan is to have to craft some variant of the Ender Crystals to cause it to respawn, but for now you're supposed to make a creeper face out of clay.
And if it were intended, why is there specifically a test that causes the dragon to not automatically respawn if you have end portal blocks in the correct quadrant of the End?
The fix should be simple, they just need to check chunks -8 to 8 (on both axes) instead of only 0 to 8.
Can confirm. Also confirmed not intended:
You will need to respawn the dragon to get the new end features. Doing so may destroy things you've built in the end, so it's something you (the player) have to initiate.
Source: http://www.reddit.com/r/Minecraft/comments/3extko/will_19s_end_gateway_work_on_18_worlds/ctjejif
This does not seem to be fixed in 15w31c. OTOH, in 15w31c using the creeper-face does turn the old portal to endstone instead of ignoring it.
I see three places in the 'apd' class that iterate from 0 to 8: purposes appear to be "find if there are any portal blocks", "replace existing portal structure with endstone", and "make sure chunks are still loaded". Only one (the "replace portal with endstone" one) was changed to iterate -8 to 8 in 15w31c.
This may be intentional: