minecraft-assets/assets/minecraft/recipes/hopper_minecart.json

{
  "type": "crafting_shaped",
  "pattern": [
    "A",
    "B"
  ],
  "key": {
    "A": {
      "item": "minecraft:hopper"
    },
    "B": {
      "item": "minecraft:minecart"
    }
  },
  "result": {
    "item": "minecraft:hopper_minecart"
  }
}