This is not a bug, but I do have a question regarding the start-up of 1.6 worlds to 1.7.  If you are prompted similar to the output below, is there a way to manually reconcile these blocks?

 

There are 17 missing blocks and items in this save.

If you continue the missing blocks/items will get removed.

A world backup will be automatically created in your saves directory.

 

Missing Blocks/Items:

RopesPlus:Confusing Arrow303

RopesPlus:Exploding Arrow303

RopesPlus:Fire Arrow303

RopesPlus:Seed Arrow303

RopesPlus:Penetrating Arrow303

RopesPlus:Rope Arrow303

RopesPlus:Torch Arrow303

RopesPlus:Warp Arrow303

RopesPlus:Redstonetorch Arrow303

PetBat:fed Pet Bat

MoCreatures:MoC_Grass

MoCreatures:MoC_Dirt

MoCreatures:MoC_Stone

MoCreatures:MoC_TallGrass

MoCreatures:MoC_Planks

MoCreatures:MoC_Leaf

MoCreatures:MoC_Log

You could use a NBT editor to edit the save file to align the names.

Or, write a mod that handles the missing event and fixes them.

But no not simple way for the end users to do it as this is a modder issue not a end user issue.

When you say the save file, are you referring to level.dat or another file that is now generated?  I'm already using NBT explorer to change over our new world gen to largeBiomes.  Most of these items are easily replaced, but the MOC blocks have me worried.  Provided that they are the blocks we are actually using, it may come down to manually correcting just these files, provided it is a one time thing.

I managed to work through this issue.  For anyone else that runs into this for Mo'Creatures, Pet Bats and/or Ropes+, the names were changed from 1.6.4 to 1.7.2 for some blocks.

 

 

Examples:

MOC_dirt is now Mocdirt (underscore removed for each of these blocks)

MOC_Planks is now MoCwoodplank

MOC_Leaf is now Mocleaves

Seed Arrow303 is now SeedArrow (no spaces or 303 for each of the arrows)

fed Pet Bat is now fed_pet_bat (spaces changed for underscores)

 

If you edit the level.dat for the world and for each of the dimensions, modify the Forced Name for each of these to the new entry.  When you start the server, be sure that you are only including the 1.7 version of any mods you had for 1.6.  Once the server startups, it will migrate to the new system.  Then, you can shut the server down and add any new mods.  Failing to do this can result in very broken worlds  (lamps for tree leaves for instance).

It seems from what you explain that Block/Item names with spaces and / or underscores do not get properly remapped. That does sort of make sense. I wonder if there is a FML fix in the works for such a thing. It may not be possible as naming by modders is so all over the place.

The registry doesnt care about any of those special characters, a string.

However if a modder changes the name between versions, there isnt anything we can do.

The modder can however as we fire a missing mapping event that lets them handle it.