The most recent snapshot (17w48a) added the ability for datapacks to include custom recipes.

Recipes with NBT tags (for example, a named or enchanted item) should work. In-game crafting, however, ignores the nbt tag and crafts as if it were not specified.

As a test, I tried two ways of doing the NBT tags for the resulting item, which should be (as an example) a diamond chestplate with Protection I.

1: As its own string, i.e.

"result": {
    "item": "minecraft:diamond_chestplate",
    "nbt": "{ench:[{id:0,lvl:1}]}",
    "count": 1
}

This results in a diamond chestplate which is not enchanted, seen below in the screenshot with the emerald. No errors are returned in the output log here.

2: With the item string (as the newer syntax for item nbt), i.e.

"result": {
    "item": "minecraft:diamond_chestplate{ench:[{id:0,lvl:1}]}",
    "count": 1
}

This crafting recipe has no result at all, seen below in the screenshot with the nether star.
The output log returns the result:

java.lang.IllegalArgumentException: Non [a-z0-9/._-] character in path of location: minecraft:diamond_chestplate{ench:[{id:0,lvl:1}]}

referring to the NBT tag itself.

In case it helps, I've also attached a zipped version of the datapack I'm using.