Mobs "control" the minecart they are riding
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Here is a world download if you want to see the bug for yourself:
http://www.mediafire.com/download/qq1vyxuxvdcq7e1/Minecart_Bug_Demo.rar
There is a cat spawn egg for your convenience.
Edit: I uploaded Picture 7 with the debug screen so you can see the version and a better view of the machine as well.
Environment
Windows 8, java 7 update 51
Linked Issues
is duplicated by14
MC-88227Mobs interacting with minecarts weirdlyDuplicateMC-95525Minecarts start moving randomlyDuplicateMC-95856Living-Entity (Mob) in minecart causes random movementDuplicateMC-98803Mobs in a minecart on a non-powered powered rail starts movingDuplicateMC-98974Villagers can move the minecart they are ridingDuplicateMC-99136Minecart with villager DuplicateMC-99450Minecarts not behaving correctly when animal is riding insideDuplicateMC-99612Mobs move while in minecartsDuplicateMC-99625Minecart bugDuplicateMC-100388Mobs in minecarts move on their ownDuplicateMC-100658Mobs will over minecartsDuplicateMC-109998Baby Villager on Minecart can push Player DuplicateMC-110889Minecarts, full velocity without powerDuplicateMC-128474Villagers control minecarts?Duplicate
Low
Created Issue:
Mobs "control" the minecart they are riding
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Environment
Windows 8, java 7 update 51.
I have tested the bug in 1.7.10 and 14w31a but it is very plausible that it affects all other 1.8 snapshots as well.
Attachments6
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Edit: I uploaded Picture 7 with the debug screen so you can see the version.
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Edit: I uploaded Picture 7 with the debug screen so you can see the version.
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Here is a world download if you want to see the bug for yourself:
http://www.mediafire.com/download/qq1vyxuxvdcq7e1/Minecart_Bug_Demo.rar
There is a cat spawn egg for your convenience.Edit: I uploaded Picture 7 with the debug screen so you can see the version and a better view of the machine as well.
is duplicated by
![[Mod] Torabi](../../../data/assets/gravatar/torabi.png){kind=small}
relates to
is duplicated by
is duplicated by
A comment with security level 'global-moderators' was removed.
Launcher.exe
![[Bot] Arisa](../../../data/assets/gravatar/mustek2.png){kind=small}
is duplicated by
is duplicated by
is duplicated by
is duplicated by
Windows 8, java 7 update 51.
I have tested the bug in 1.7.10 and 14w31a but it is very plausible that it affects all other 1.8 snapshots as well.Windows 8, java 7 update 51
is duplicated by
is duplicated by
is duplicated by
is duplicated by
blocks
![[Mod] Neko](../../../data/avatars/users/92901.png){kind=small}
is duplicated by
is duplicated by
is duplicated by
Confirmed for: 1.12
Villager trying to go back to his Village
![[Mod] Michael Wobst](../../../data/avatars/users/37868.png){kind=small}
relates to
I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Here is a world download if you want to see the bug for yourself:
http://www.mediafire.com/download/qq1vyxuxvdcq7e1/Minecart_Bug_Demo.rar
There is a cat spawn egg for your convenience.Edit: I uploaded Picture 7 with the debug screen so you can see the version and a better view of the machine as well.
A code analysis by Xcom6000 can be found here.
![[Mod] tryashtar](../../../data/avatars/users/41963.png){kind=small}
![[Mojang] Grum (Erik Broes)](../../../data/assets/gravatar/grum.png){kind=small}
[Mojang] Grum (Erik Broes)I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Here is a world download if you want to see the bug for yourself:
http://www.mediafire.com/download/qq1vyxuxvdcq7e1/Minecart_Bug_Demo.rar
There is a cat spawn egg for your convenience.Edit: I uploaded Picture 7 with the debug screen so you can see the version and a better view of the machine as well.
A code analysis by
Xcom6000 can be foundhere.I was trying to create a machine that would take mobs and put them in minecarts when i noticed that some mobs moved their minecarts and others did not. This was weird, as mobs do not have pathfinding when riding in minecarts. For example, zombies riding minecarts do not react at all when close to villagers. Therefore it would make sense that mobs should not be able to control the minecart they are riding as they do not have pathfinding.
To investigate the cause of this bug I set up a system that places mobs in minecarts and tested it with creepers. Pictures 1 shows a creeper being placed in the mechanism. The minecart eventually comes to a stop (picture 2), showing that the creeper did not control the minecart at all. Placing cats next to the creeper (picture 3) also caused no response, which further shows that the creeper was not in control of the minecart.
For the second test, I placed a cat close to the rails and then summoned the creeper so that it would flee and thus BE IN MOTION when the minecart picks it up (picture 4). In picture 5 we see that the creeper goes forward in a similar matter to the first test. However, the creeper then stops and starts going backwards (picture 6), which is very weird.
We saw from the previous test that the cat should not affect the creeper when it is riding the minecart, and therefore there is no reason why test 1 and 2 should have different results. The only difference is that the creeper had momentum BEFORE it was picked up in test 2, whereas in test 1 it was stationary. My hypothesis is that when mobs enter minecarts, they keep whatever pathfinding they had before and try to get to the direction they were going before by controlling the minecart.
To conclude, mobs should not control minecarts, but test 2 shows that they sometimes can, and thus this bug should be fixed.
Here is a world download if you want to see the bug for yourself:
http://www.mediafire.com/download/qq1vyxuxvdcq7e1/Minecart_Bug_Demo.rar
There is a cat spawn egg for your convenience.Edit: I uploaded Picture 7 with the debug screen so you can see the version and a better view of the machine as well.
![[Mod] violine1101](../../../data/avatars/users/92858.png){kind=small}
is duplicated by
This relates to:
It seems like mobs in Minecarts aren't able to control them (except chicken jockeys). This is different to boats and seems to cause some problems.
When a minecart picks up for example a entity which is moving (like a Zombie), it will some kind of take the Motion value causing it to stuck for example at powered rails next to a block.
Confirmed for
- 15w44b This only relates to
MC-64836as in this case here it also happens without the minecart being on rails
This seems to happen for mobs which AI is overridden by default, so chickens and spiders:
/summon MinecartRideable ~ ~ ~ {Passengers:[{id:"Chicken",Passengers:[{id:"Zombie"}]}]}
/summon MinecartRideable ~ ~ ~ {Passengers:[{id:"Spider",Passengers:[{id:"Zombie"}]}]}
Note: For spiders the movement seems to be inversed so they move away from their target
@Vincenzo Cilino Don't worry it'll get fixed! I can't imagine them going into the release in their current state. Minecarts are totally useless currently, as we can't use them to transport entities, and we can't use them to travel either (chunks don't load and we get stuck in them, forcing a relog or crashing).
Of course it's annoying but we have to be more patient with showstopper bugs like this. Cosmetic bugs get fixed quickly because they're easier to isolate, are more obvious, thus easier to fix.
But I agree minecarts should receive some sort of priority because they are REALLY broken. This one, MC-89915 & MC-64836 are the most important ones.
Not to be nitpicking but, how exactly does the bug system work? 1 week old, insignificant bugs with 2 votes get fixed right away (I understand they can be easy fixes) while a very important one like this, that exist since a good while, that crashes the game or the server, has accumulated 97 votes, is not even being looked into or assigned to anyone yet?
Minecarts have been unuseable for almost 2 months now and none of the related bugs have even been assigned yet (this one is the most important, then MC-92165 and MC-64836).
This is not to complain, it's just to understand, and to not lose my time reporting or voting for issues for nothing.
See MC-64836.
@moss gridley
Present issue being the most annoying, the 2nd worse is MC-92165 (near impossible to transport entities), and to a lesser degree MC-64836 (entities control minecarts, if you manage to get them in).
I'm really sick of minecarts in the current state too. I think they're important enough to be considered seriously.
142 voters isn't enough, it hasn't been assigned yet...
Hey! I just wanted to tell You, that I dont think that that is a duplicate of MC-64836 !!! Because that bug is about path finding ans This one is about Minecarts which are not stopping. I might be wrong but I dont think so.
Duplicates MC-64836
@Jeffrey King
I know, the mobs controlling minecarts is MC-64836. And it won't get fixed for 1.9. It's very likely that this issue will make it into the release too.
We can discuss these issues on the reddit thread I created for that (my previous post). Unfortunately, no one cares about reddit, not even Mojang, the Devs, the mods, and the community.
Blocked by MC-64836
![[Mod] Les3awe](../../../data/avatars/users/79847.png){kind=small}
MC-64836 describe this issue?
Confirmed for 1.11. Not fully blocked by MC-64836: minecarts with slimes do not interact with powered rails properly. A cow in a minecart will stop when crossing an unpowered powered rail, for example.
While building a villager trading area which uses powered and unpowered rails to transport the villages to their designated trading point, the villagers were moving the minecarts on their own.
I believe the same issue was reported (MC-64836) but has been marked as resolved...?
I am not sure if this is still an existing 'bug' or an issue that has returned.
I cannot upload a picture of a villager moving a minecart but I made a short video: https://youtu.be/6xLJM9DOhME
I usually play Minecraft with Optifine, but this issue still exists on full Vanilla in both creative and survival worlds.
After a bit more testing, I have determined the following things:
-Mobs in minecarts actually track a block, not a direction; they will always face this block when in a minecart.
-Mobs will continue to go towards that block after the minecart is broken and they are free to move.
-Mobs will continue to target that block even if the block is located in unloaded chunks.
Only cows and skeletons can control minecarts I think
Confirmed for
/summon Zombie ~ ~1 ~ {Invulnerable:1,HealF:0.1,Riding:{id:Chicken,HealF:0.1,Riding:{id:MinecartRideable}}}This even overwrites NoAI of the chicken, see also
MC-41566However it seems like mobs in minecarts aren't as fast as players in minecarts when they are driving rather fast (without pressing any key), but when the minecarts slow down, the mob is faster than the player resulting it both player and mob travelled the same distance at the end.
Here's a video showing a villager "controlling" a minecart. It's standing on an unpowered rail and should remain still as long as there's no power. But as soon as the villager tries to move or turn, the minecart goes off. This is in snapshot 15w38a.
https://youtu.be/ASM7yMUw1e4
Edit: Still present in 15w40b.
Edit 2: looks like it's been fixed in 15w41b.
Seems like the fix also removed the ability for players to control the minecart.
It is unlikely this was fixed. There is a bug that minecarts cannot be controlled in this snapshot, see
MC-89946. Reopening.Controllable minecarts have been fixed in 15w44b, making this bug resurface.
No surprise there...
Confirmed for
/summon MinecartRideable ~ ~1 ~ { Passengers:[ { id:"Chicken", Health:0.1f, Passengers:[ { id:"Zombie", Invulnerable:1b, Health:0.1f } ] } ] }Marcono: Still affects all mobs. They try to path find somewhere and start moving in that direction, which moves the minecart. Easily reproducible by putting a zombie in a minecart and spawning a villager nearby.
Cannot confirm for only zombie as passenger of a minecart, please test this
Can still confirm without the villager.
Oh I see I miss understood this. I will probably create a new report because chicken jockeys can control minecarts that are not on rails as well.
But isn't this behaviour intended as it was (currently is not anymore) the same for boats as well.
Still in 15w45a.
Confirmed still in 15w47a.
"Fix version: Far Future Version - 1.10"
Is this serious?
Yep.
Still in 16w06a
A villager in a minecart was able to push me against the direction I was walking. He - on wheels - was able to overpower me. This makes no sense and breaks a lot of functionality. (16w07a)
I told all my Friends to vote for This. Also I told many creators of big Iron farms which Are using This principle to vote and tell their Friends. And yesterday I tweeted it to Searge. That's everything I can so and what You could do too.
It will eventually get fixed, just not for 1.9.
I know. But I Want it to get fixed for 1.9
Confirmed for 1.9pre4
Why was this issue postponed?
I'm sorry if this question is unreasonable because I'm new to this bugtracker.
Tim Schumacher I don't know for sure, but I assume because there were myriads of even more urgent bugs to fix, and they had to get out the release version out at some point.
Although this bug here is quite annoying for mainly Survival farms, there really were many other more "gamebreaking" bugs that had to be attended to.
The mods don't like it if we meta-discuss in the comments (writing something that doesn't help the bugpost like you and I do now) but as you were new, I had to ;-;
If you got any questions to the bugtracker, maybe post here on the bugtracker-Reddit or PM the mods there or so }=)
Welcome to the bugtracker 🍪😸
This issue was postponed because it will require a significant code rewrite to fix properly. Rideable entities such as minecarts and horses were designed with certain assumptions – like the entity riding would always control it. That mobs didn't under some circumstances was more of a hack than the systems working together in a well-designed way, and some of those systems have undergone significant upheaval over the past several versions. It's hard to produce reliable, correct behavior under those circumstances – hacks tend to be fragile, and extremely dependent on the underlying code. When that code is changed in order to improve it or fix other behavior, the hacks break. Rather than try to hack it together again, Mojang would rather fix the problem correctly, by rewriting the legacy code. This would have taken more development time and testing time than was reasonable for the current release, which had been in development for much longer than was typical for Minecraft, resulting in the longest delay between releases in the history of the game. 1.9 has a huge number of changes, new content, and bug fixes, and they wanted to get those out to people who don't play the snapshots, which were relatively stable by this time. Ripping into delicate code would have likely introduced new bugs, and made the game too unstable to release for a significant period of time, possibly several more months. There will definitely be some smaller releases in between 1.9 and 1.10 that will hopefully address some of the important issues that couldn't be fixed for 1.9.
I can confirm this for 1.9. The odd thing is I did not have this problem in any of the 1.8 versions. Now my villager sorting system is half broken until this is fixed. (The villagers do eventually go down the track, but it's very annoying to have to wait sometimes minutes for them to arrive instead of the 5 seconds it's supposed to be)
In 1.9 unpowered-powered rails don't prevent minecarts movement as in previous version so, In my opinion, this bug has become more noticeable. Patching powered rails may be easier and could help some contraptions bugged.
Confirmed for
Confirmed for 1.10.2
Villager trying to go back to his Village
Still in 1.11. Please update Affected Versions.
Still in 1.11.2. Please update the Affected Versions. Thank you
Please do not mark unreleased versions as affected.
You don't have access to them yet.
Confirmed for 1.12
why is some major bug like that postponed? whats the point of putting a mob into a cart if it can walk around like free? Makes carts pretty useless in regards of actual working contraptions always have to push the mobs off the track wich is a workaround but by no means a fix
Jack, see this comment
so the reason this isnt fixed is simply chikenjokeys? seems worth postponing rendring anything involving carts and mobs useless... maybe the chiken jokeys and whatever else is affected by this should be changed.... i dont get how a gameruining bug like this isnt beeing worked on.....
Here's what I don't get: Why do you assume the entity riding it will always control it? There should be far more cases of where it shouldn't, than when it should, so doesn't it make sense to assume the rider doesn't control it unless it's the player/jockey?
I'm not a programmer, but my logic suggests it would make sense to code for:
Those rules would have far fewer exceptions than coding for every mob in the game to not control an entity, and it wouldn't increase unless a new jockey was added (which doesn't happen that often compared to how often new mobs are added)
Eta740, Jack for discussions of the nature of "the developers should" / "the developers should not" please refer to the Mojira subreddit. You can create a text post there to discuss this matter.
The issue with entity controlling what they are riding is historical; Minecraft never underwent a proper design and planning phase prior to implementation (or at least not one that could have foreseen its future success). (When Notch made Minecraft and added minecarts your argument was the very other way around.)
I'm suggesting how it can be fixed with quite more detail than the average complaint. Besides, when minecarts were first added, there was still more cases of mobs not controlling than when they did. The only jockey at that time would've been the spider jockey (if they even existed at that time), and then there's the player. Meanwhile, you still have pigs, cows, and chicken. Not sure if the nether came before, but if they did, there's also the pigman and ghast.
@Eta740 don't forget wither skeleton and stray in case the Skeleton trap is in the nether/cold biome.
@Guerin Since 1.11, they don't spawn anymore, because they are separate entities and no longer variants of a skeleton. But I guess it would be fine to make any rider control a horse, in case map makers want to use it.
@Eta740 I guess I didn't realise that this change affected tat. So my super idea for an unusual wither skeleton farm is no longer usable.
The behaviour to change all entity's controlling the minecart is quite simple. In EntityMinecart.java a simple if statement can be changed to make only players control the minecart.
line 545:
changed to
Changing EntityLivingBase to EntityPlayer makes the minecart only be controllable by the player.
I think this is intentional, because when you press the button for moving forward, the minecart moves forward, and if you press the button for moving backwards, the minecart moves backwards.
This also happens to the mobs, but they are not players, so their code tells them to move forward, and the minecart is programmed to move forward when the thing inside of it gives the signal that they are, or want to move in any direction.
The thing is that they can override powered rails or inclines, which a player can't actually do, so when they pathfind to a selected spot they become impossible to manage and makes minecarts useless when it comes to mob storage or transport.