Cured villagers sell bookshelves for 1 emerald and buy books for 1 emerald, allowing players to easily get an unlimited amount of emeralds

There's a similar exploit, try curing a cartographer twice.  You can buy glass at 4 per emerald, then sell it as panes for 1 emerald per pane.

In progress? I think the developers are missing the big picture about villager exploitation.

There are countless ways of trading that can be considered "exploiting", even ones that are way easier to access than the librarian bookshelf "exploit" (and any of the other ones mentioned in the previous comments of this report). One of the many examples (that is a big number that is maybe in the hundreds but really hard to actually determine)? The easiest "exploit" on the top of my head is getting two wood planks and two flint to get a fletching table. Convert a villager to get a fletcher using the fletching table and the short answer is getting 32 emeralds a day by gathering only two stacks of wood and trading it in as sticks, EZ! With the librarian "exploit", you have to access a lectern by getting some wood slabs and a bookshelf, or finding one. You then have to then level up the librarian with a bit of sugar cane crafted into paper, or by buying enchanted books if you want, but you need the bookshelf trade. When the librarian is leveled up, cross your fingers as you have a 1/3 chance of getting unlucky and having to start with a new librarian. If you successfully get the book trade with the bookshelf, brew a potion of weakness using a spider eye, a brown mushroom, and a sugar to get a fermented spider eye (not to mention you can't do that without going all the way into the Nether to find a fortress for blazes; you need blaze powder to brew), then gain access to a pricy golden apple and then put your librarian under the painful process of being zombified and cured. Enjoy your "exploited" librarian that you actually worked hard for! These two villager "exploits" I mentioned will get you a lot of emeralds, but the "exploited" librarian is clearly harder to get than the "exploited" fletcher. You may have to break less blocks for the "exploited" librarian, but the librarian will only give you 24 emeralds a day instead of 32 emeralds a day for the fletcher by trading in wood, which is actually almost as easy to find as the books from the librarian. The "exploited" librarian trade also make sense, maybe the librarian wants you to do the manual labor of getting books out of bookshelves. In summary, if you can get many emeralds in a much easier way than librarians, then "exploited" librarians are not the problem here.

If librarian book trades are not the villager exploit problem, then what is? I know that I should only explain why fixing this is pointless, but I will go a step further to bring light on an actual exploit for villagers, which also supports why the librarian bookshelf to book trade shouldn't be fixed. Due to the multitude of "exploits" you could use to eventually gain tons of emeralds, they are very easy to obtain if you live in a village. I like that villager trading gives more resources and allows you to get things in a way cheaper manner than just crafting them in the long run, so there would be absolutely no point in removing a small piece of that functionality. This is why I put no more effort into mentioning more examples of "exploits", which are actually a good mechanic of the game that you always have to put work into. Since emeralds are really abundant after time and careful planning, the balance of trading really boils down to what you can buy from the villagers, and that is where we find the true exploit. No, it isn't diamond armor for an emerald, it's actually way more overpowered and easy to access. The true exploit is MC-150777, and it is especially exploitable for librarians. You can find every enchantment from the very beginning of the game without any tools, armor, or even any resources. All you have to do is find a village and a lectern, which can also be crafted with a bookshelf and some slabs. Unlike the "exploited" librarian, you are actually set after the lectern, and there is a 100% chance that you will get any enchantment you need if you break and replace the lectern enough times (as opposed to a 2/3 chance of getting an "exploited" librarian). Doing this requires no resources or anything, just a mere fraction of the time it takes to AFK fish for enchantments you want. Once you find the enchantment you want, it may cost a bit of emeralds, but like I said, they are very easy to obtain. For each librarian you find or employ, you can buy any enchantment you want with minimal effort or time compared to doing other tasks for enchanted books.

Since cheap and selectable enchanted books are an actual problem unlike an essential mechanic to our new trading system, I will come up with some ideas on how to fix MC-150777. The way I would fix this is to remove the novice level enchanted book trade from the librarian, as well as the novice level enchanted iron sword trade from the weaponsmith because early looting is really powerful (I know this wouldn't really be a fix to MC-150777 because we still would be able to cycle through trades in a much less OP way). If MC-150777 should be completely fixed, make each villager had a randomized "trade seed" that keeps their trades consistent, them we wouldn't be able to get easy enchanted books of our choice, so if we don't like an enchanted book that a librarian sells, we could convert it to a weaponsmith and maybe find a good enchanted iron sword.

To shorten that all up, MC-153334 isn't even a real problem compared to getting any enchanted books we want with little effort.

This is a bug tracker, not a discussion forum. If you wish to discuss this ticket, please head over to /r/Mojira.

first of all, what a snitch 😃 😞
Second, HOW was this fixed? It is not enough for us to know that it has been fixed!!
Third, I agree this is not an exploit, given that villagers can only trade a few times per day and it takes a LOT of effort to get a few of them transformed, im really disappointed to see this go!