How do you convert a custom-item /give command into a villager trade? (in general) [duplicate]

The CanPlaceOn list and all other item data is inside the tag compound tag:

{
  Items:[ 
    {
      id: "minecraft:wooden_button",
      Count: 1b,
      Slot: 0b,
      tag:{
        CanPlaceOn:[
          "minecraft:log"
        ]
      }
    }
  ]
}

Example command for 1.12−:

/setblock 294 5 -1251 minecraft:chest 0 replace {Items:[{Count:1b,Slot:0b,id:"minecraft:wooden_button",tag:{CanPlaceOn:["log"]}}]}

Example command for 1.13+:

/setblock 294 5 -1251 minecraft:chest{Items:[{Count:1b,Slot:0b,id:"minecraft:wooden_button",tag:{CanPlaceOn:["minecraft:log"]}}]}

Item NBT structure can be found on this wiki page.

Common mistakes include:

• forgetting tag:

  {
    id: "minecraft:wooden_button",
    Count: 1b,
    CanPlaceOn: [
      "minecraft:log"
    ]
  }
  

• attempting to put it inside the item ID:

  {
    id: "minecraft:wooden_button{CanPlaceOn:['minecraft:log']}",
    Count: 1b
  }