Minecraft Forge 1.10.2-12.18.3.2185 - Fully-defined variants in Forge's blockstates format - http://www.minecraftforge.net/forum/index.php?topic=44165.0

dirt_slab.json

{
  "forge_marker": 1,
  "defaults": {
    "model": "half_slab",
    "textures": {
      "top": "blocks/dirt",
      "bottom": "blocks/dirt",
      "side": "blocks/dirt"
    }
  },
  "variants": {
    "snowy=false,variant=dirt": {
      "__dummy": "Forge's blockstates format requires all non-array values of `variants` to be objects with at least one property"
    },
    "snowy=true,variant=dirt": {
      "__dummy": "Forge's blockstates format requires fully-defined variants to have something other than an object as their first value",
      "textures": {
        "top": "blocks/snow"
      }
    },
    "snowy=false,variant=grass": {
      "model": "betterwithmods:grass_slab"
    },
    "snowy=true,variant=grass": {
      "__dummy": "See snowy=true,variant=dirt",
      "textures": {
        "top": "blocks/snow",
        "side": "blocks/grass_side_snowed"
      }
    },
    "snowy=false,variant=mycelium": {
      "__dummy": "See snowy=true,variant=dirt",
      "textures": {
        "top": "blocks/mycelium_top",
        "side": "blocks/mycelium_side"
      }
    },
    "snowy=true,variant=mycelium": {
      "__dummy": "See snowy=true,variant=dirt",
      "textures": {
        "top": "blocks/snow",
        "side": "blocks/mycelium_side"
      }
    }
  }
}