Add validate_t

[metanivek]

While experimenting with atdgen, I came across an edge case when trying validations and untypable JSON.

If I use the following, I get a build warning about deprecation of the json type.

type json <ocaml module="Yojson.Safe"> = abstract

If I add an explicit type (t="t") to address the warning, compilation fails with Unbound value Yojson.Safe.validate_t, so this PR adds it. Since it appears that the json type is disappearing, I also made validate_json an alias to validate_t as the canonical definition.

[Leonidas-from-XIV]

The type json will be removed removed in 2.0.0, atdgen will need to update to use Yojson.Safe.t.

In fact, I feel like we should probably also remove validate_json since this function doesn't seem to serve any purpose, @panglesd?

[metanivek]

Got it. I’m happy to remove validate_json here. atdgen does work with Yojson.Safe.t but it needs validate_t to exist when using validations.

[Leonidas-from-XIV]

I think in such case it would be more reasonable to define a module that wraps Yojson.Safe.t in your code and provides validate_t. Or change atdgen to allow injecting a validation function in another way.

[metanivek]

Agreed. This seems like a good opportunity to break this connection between the two libraries since it is really an atdgen concern.

[Leonidas-from-XIV]

Closing this in favor of #136. Thanks @metanivek for pointing our attention to the fact that we have old left-over code that doesn't work, let's make 2.0.0 the best release we can.

[metanivek]

@Leonidas-from-XIV happy to help!

[MisterDA]

Just had the same problem. Could you explain how to turn off the validation for the json type? Every combination I'm using turn out to be wrong with the code atdgen.2.2.1 generates.
You could also point to this issue from the changelog.

[metanivek]

@MisterDA I missed your comment previously, but I came back to this the other day and realized it wasn't working. I made a PR that should fix this as of atdgen.2.9.1 release. 🎉