cue vet with bytes type

[joelanford]

I'm hoping to use cue vet to vet a JSON struct that contains a base64 encoded string, so I'd like my cue schema to contain a bytes field. However cue vet interprets my JSON struct as a string (technically, it is) and complains that it is not a bytes (even though it was exported from a bytes field). Is there any way to vet base64 encoded strings as bytes?

Given the follow files:

schema.cue

package hello
#Bytes: {
   base64data: bytes
}

bytes.cue

package hello
#Bytes & {
    base64data: 'Hello, World'
}

I expect to be able to export JSON and then vet it, but vet fails.

$ cue export schema.cue bytes.cue > bytes.json
$ cat bytes.json
{
  "base64data": "SGVsbG8sIFdvcmxk"
}
$ cue vet bytes.json schema.cue -d '#Bytes'
base64data: conflicting values "SGVsbG8sIFdvcmxk" and bytes (mismatched types string and bytes):
    ./bytes.json:2:17
    ./schema.cue:2:14

[myitcv]

@joelanford welcome to the CUE project!

This looks like a bug, or more specifically a feature we haven't yet implemented totally in cmd/cue. This is very much analogous to recent work in the protobuf space, where data can be interpreted (imported/vetted/whatever) in the context of a specific schema. Here the transformation from JSON string field to bytes is something that could be expressed by the -d flag, and hence checked.

Please can you raise a feature request issue for this?

[amilicms]

Hello, I've also run into this issue with CUE v0.8.0. I would expect that the bytes would interpret the string as base64 and validate accordingly. My current work around is something along the lines of the following:

import "encoding/base64"

#base64Bytes: input={
	string
	#valid: base64.Decode(null, input)
}

b: #base64Bytes & "aGVsbG8sIHdvcmxkIQo="
// c: #base64Bytes & "$$$" // uncomment to see error

Ideally I would like to be able to use the bytes type directly.