What server are you running?

Ooo nice idea, but it's actually quite a tricky one, as there's no entities involved in that situation.

With commands there's no way to "select blocks of type" and dispensers and vines are both blocks. And while dropped shears are an entity, dispensers don't spit them into the world for selecting, but keep them in their inventory.

You could use a dropper and execute on the shears that get spit out, then if they're touching a vine, setblock to air, summon a vine item, then finally replaceitem shears back into the droppers inventory with damage applied. It's all pretty tricky, especially that last part.

Another way is to mark a dispenser with an entity from which you can run commands. There's a complex automated way to do this with scoreboard "used" objectives, invisible armour stands and raycasting to find where the dispenser was placed.

But to start with, a more manual way would be to put an item frame on top of the dispenser in game. Then you can run something like this in your main tick function:
execute as @e[type=minecraft:item_frame] at @s if block ~ ~-1 ~ minecraft:dispenser[triggered=true] run function yournamespace:yourfunction

Then in the "yourfunction.mcfunction" file run a bunch more execute commands to find which way the dispenser is facing, find if there's a vine in the block space in front of the dispenser, and if so setblock to air and summon the dropped vine item there.


I don't know how helpful all the above is, but that's how I would approach it. I don't personally have time to help you learn all the commands etc, and as I don't personally use vines much I probably wouldn't make this datapack myself, sorry.


But yeah, I learnt by watching a bunch of Youtube videos where they explain commands. Then once I had a bit of a handle on the commands, I found datapacks that looked like they did similar things, downloaded them and read through the mcfunction files. Then there's the wiki, which can be confusing to begin with, but helpful later on. It also helps to write and run single commands using the in game autocomplete when you type "/" in chat, then copy them into your function files. Knowing how to Google the right keywords is key to finding the info you need.


Finally, if you're interested in programming, I'd suggest not wasting time with MC commands, and instead learn Java and how to make Forge mods. You can do much more complex things that way, and knowledge of Java can translate into things outside of MC, and will enable you to easily learn other languages in the future if you so desire.


Wow this ended up being really long.
Hope this helps.

No the villager breeding mechanic is different to other passive mobs.